A Phase 3, Randomized, Stratified, Observer-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety, and Immunogenicity of mRNA-1273 SARS-CoV-2 Vaccine in Adults Aged 18 Years and Older
Phase: PHASE3
Conditions: SARS-CoV-2
Sponsor: ModernaTX, Inc.

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
Confidential 
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CLINICAL STUDY PROTOCOL 
Protocol Title: 
A Phase 3, Randomized, Stratified, Observer-Blind, 
Placebo-Controlled Study to Evaluate the Efficacy, Safety, and 
Immunogenicity of mRNA-1273 SARS-CoV-2 Vaccine in 
Adults Aged 18 Years and Older  
Protocol Number: 
mRNA-1273-P301 
Sponsor Name: 
Legal Registered Address: 
ModernaTX, Inc. 
200 Technology Square 
Cambridge, MA 02139 
Sponsor Contact and 
Medical Monitor: 
 
 
ModernaTX, Inc. 
200 Technology Square, Cambridge, MA 02139 
Telephone: 
 
e-mail: 
Regulatory Agency 
Identifier Number(s): 
IND: 19745 
Amendment Number: 
10 
Date of Amendment 10: 
07 Apr 2022 
Date of Amendment 9: 
10 Sep 2021 
Date of Amendment 8: 
23 Mar 2021 
Date of Amendment 7: 
10 Feb 2021 
Date of Amendment 6: 
23 Dec 2020 
Date of Amendment 5: 
11 Nov 2020 
Date of Amendment 4: 
30 Sep 2020 
Date of Amendment 3: 
20 Aug 2020 
Date of Amendment 2: 
31 Jul 2020 
Date of Amendment 1: 
26 Jun 2020 
Date of Original Protocol: 
15 Jun 2020  
NCT #: NCT04470427
PPD
PPD
PPD
PPD

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
 
Confidential 
 
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CONFIDENTIAL 
All financial and nonfinancial support for this study will be provided by ModernaTX, Inc. The 
concepts and information contained in this document or generated during the study are considered 
proprietary and may not be disclosed in whole or in part without the expressed written consent of 
ModernaTX, Inc. The study will be conducted according to the International Council for 
Harmonisation (ICH) Technical Requirements for Registration of Pharmaceuticals for Human 
Use, E6(R2) Good Clinical Practice (GCP) Guidance. 
 

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
 
Confidential 
 
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Protocol Approval – Sponsor Signatory 
Study Title: 
A Phase 3, Randomized, Stratified, Observer-Blind, 
Placebo-Controlled Study to Evaluate the Efficacy, Safety, and 
Immunogenicity of mRNA-1273 SARS-CoV-2 Vaccine in Adults 
Aged 18 Years and Older 
Protocol Number: 
mRNA-1273-P301 
Protocol Version Date: 07 Apr 2022 
 
 
Protocol accepted and approved by: 
Please see eSignature and date in the 
last page of the document. 
 
 
 
 
ModernaTX, Inc. 
200 Technology Square 
Cambridge, MA 02139 
Telephone: 
 
 
Date 
 
 
 
 
 
PPD
PPD
PPD

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
 
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DECLARATION OF INVESTIGATOR 
I have read and understood all sections of the protocol entitled “A Phase 3, Randomized, Stratified, 
Observer-Blind, Placebo-Controlled Study to Evaluate the Efficacy, Safety, and Immunogenicity 
of mRNA-1273 SARS-CoV-2 Vaccine in Adults Aged 18 Years and Older” and the most recent 
version of the Investigator’s Brochure. 
I agree to supervise all aspects of the protocol and to conduct the clinical investigation in 
accordance with the current protocol, the International Council for Harmonisation (ICH) 
Technical Requirements for Registration of Pharmaceuticals for Human Use, E6(R2) Good 
Clinical Practice (GCP) Guidance, and all applicable government regulations. I will not make 
changes to the protocol before consulting with ModernaTX, Inc. or implement protocol changes 
without institutional review board (IRB)/independent ethics committee (IEC) approval except to 
eliminate an immediate risk to participants. 
I agree to administer study treatment only to participants under my personal supervision or the 
supervision of a sub-investigator. I will not supply study treatment to any person not authorized to 
receive it. I also agree that persons debarred from conducting or working on clinical studies by any 
court or regulatory agency will not be allowed to conduct or work on studies for the Sponsor or a 
partnership in which the Sponsor is involved. I will immediately disclose it in writing to the 
Sponsor if any person who is involved in the study is debarred, or if any proceeding for debarment 
is pending, or, to the best of my knowledge, threatened. 
I will not disclose confidential information contained in this document including participant 
information, to anyone other than the recipient, study staffs, and members of the IRB/IEC. I agree 
to ensure that this information will not be used for any purpose other than the evaluation or conduct 
of the clinical investigation without the prior written consent from ModernaTX, Inc. I will not 
disclose information regarding this clinical investigation or publish results of the investigation 
without authorization from ModernaTX, Inc. 
The signature below provides the necessary assurance that this study will be conducted according 
to all stipulations of the protocol, including statements regarding confidentiality, and according to 
local legal and regulatory requirements, US federal regulations, and ICH E6(R2) GCP guidelines. 
 
Signature of Principal Investigator 
 
 
Date 
 
 
 
 
 
Printed Name of Principal Investigator  
 
 

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
 
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Protocol Amendment Summary of Changes 
DOCUMENT HISTORY 
Document 
Date 
Amendment 10 
07 Apr 2022 
Amendment 9 
10 Sep 2021 
Amendment 8 
23 Mar 2021 
Amendment 7 
10 Feb 2021 
Amendment 6 
23 Dec 2020 
Amendment 5 
11 Nov 2020 
Amendment 4 
30 Sep 2020 
Amendment 3 
20 Aug 2020 
Amendment 2 
31 Jul 2020 
Amendment 1 
26 Jun 2020 
Original Protocol 
15 Jun 2020 
Amendment 10, 07 Apr 2022: Current Amendment 
This amendment is considered to be substantial based on the criteria set forth in Article 10(a) of 
Directive 2001/20/EC of the European Parliament and the Council of the European Union. 
Main Rationale for the Amendment: 
1. To provide guidance to the investigators in providing a booster dose to participants with 
breakthrough coronavirus disease 2019 infection after primary series. 
2. To include immunogenicity analysis for Part C as a secondary objective of the study. 
Summary of Major Changes From Protocol Amendment 9 to Protocol Amendment 10:  
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version 
and date. 
To reflect the new version 
and date of the protocol. 
Title Page, Protocol Approval Page 
Updated Sponsor contact. 
To reflect personnel change. 
Section 1.2 (Schema) 
Updated Figure 1 and 
Figure 2.  
To reflect Part C as 
described elsewhere in the 
current protocol. 

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
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Section # and Name 
Description of Change 
Brief Rationale 
Section 1.1 (Synopsis), Section 2.3.2 
(Risks from Study Participation), 
Section 2.3.3 (Overall Benefit/Risk 
Conclusion), Section 4.1.3 (Part C, the 
Booster Dose Phase) 
Text updated to reflect the 
current benefit-risk profile of a 
booster dose of mRNA-1273 
based on cumulative evidence.  
Additional evidence 
informing the benefit-risk 
profile of booster dose from 
the ongoing Moderna 
Phase 2a study 
(mRNA-1273-P201) has 
become available since the 
previous amendment. 
Section 1.1 (Synopsis), Section 2.3.2 
(Risks from Study Participation),  
Section 4.1.3 (Part C, the Booster Dose 
Phase), Section 4.2 (Scientific 
Rationale for Study Design) 
Updated sections to generally 
reference variants rather than a 
specific variant. 
To encompass a broad range 
of emerging variants.  
Section 1.1 (Synopsis), Section 3 
(Objectives and Endpoints), 
Section 9.5.3 (Immunogenicity 
Analyses) 
For Part C, immunogenicity 
analysis of BD vaccine 
response will be performed 
using the noninferiority tests 
of the 2 null hypotheses based 
on the 2 key secondary 
endpoints: Ab GMT and 
seroresponse rate at 
BD-Day 29 in Part C 
compared with Ab GMT and 
seroresponse rate at Day 57 
(28 days after the second dose 
of the primary series of 
mRNA-1273). 
To provide immunogenicity 
analysis plan relevant to the 
provision of a booster dose 
in Part C.  
Section 1.1 (Synopsis), Section 4.1.1 
(Part A, the Blinded Phase), Section 
8.1.3 (Convalescent Period Starting 
with the Illness Visit), Section 11.1 
(Appendix 1: Schedules of Events, 
Table 19)  
Clarified that the duration of 
the daily telemedicine visits 
may extend past the 28-day 
Convalescent Period. 
The Convalescent Period 
duration as presented in the 
Schedule of Events is 
28 days; however, text was 
added to clarify that 
telemedicine visits may 
occur outside of this window 
depending on the duration of 
symptoms. 

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
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Section # and Name 
Description of Change 
Brief Rationale 
Section 1.1 (Synopsis), Section 4.1.1 
(Part A, the Blinded Phase), Section 
6.4.2 (Concomitant Medications and 
Therapies)  
Occasional references to parts 
of the study (eg, “Part A 
only”) in regard to particular 
procedures, requirements, or 
prohibitions have been 
removed from protocol 
sections that are specific to the 
study part and/or where these 
apply to all parts of the study. 
To remove redundancies that 
did not improve clarity. 
Section 1.1 (Synopsis) Section 4.1.2 
(Part B, the Open-label Observational 
Phase), Section 4.4 (End of Study 
Definition), Section 7.2 
(Discontinuation of Study Treatment) 
Clarified that a participant who 
did not receive a second dose 
of IP will have a study follow-
up of 25 months after first 
dose of IP. 
To address participants who 
may not have had the second 
dose of their original IP 
assignment following 
randomization. 
Section 1.1 (Synopsis), Section 8.2 
(Safety Assessments), Section 8.3.3 
(Adverse Events of Special Interest), 
Section 9.5.2.1 (Adverse Events), 
Section 11.1 (Appendix 1: (Schedules 
of Events) 
Added AESIs as an assessment 
for Part C (for participants 
who receive the BD). 
Removed reference to AESI in 
Schedule of Events tables 
specific for Part A and Part B. 
To clarify that AESIs will be 
collected in Part C for 
participants who receive the 
BD. 
Section 1.1 (Synopsis), Section 9.5.2.1 
(Adverse Events) 
Clarified the analysis sets used 
for safety analyses. 
To clarify which analysis set 
will be used for specific 
parts of the study. 
Section 4.4 (End of Study Definition) 
Clarified the timing of the 
final visit.  
To clarify when the final 
study visit will occur for 
participants who missed the 
second dose and for 
participants who entered 
Part C and had a BD-3 visit 
later than Day 759 (Month 
25). 
Section 5.1.2 (Exclusion Criteria) 
Removed text specifying 
“Part A only” for exclusion 
criteria #4, #6, #11, #13, and 
#14; added text clarifying that 
exclusion criterion #10 is 
applicable to Part A only.  
To account for the addition 
of Part B and Part C to the 
study, exclusion criteria 
were updated to reflect 
applicability of criteria to 
Part B and Part C. 

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07 Apr 2022 
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Section # and Name 
Description of Change 
Brief Rationale 
Section 6.3 (Study Treatment 
Compliance), Section 7.2 
(Discontinuation of Study Treatment), 
Section 7.3.1 (Participant Withdrawal) 
Added participants who are 
withdrawn from the study due 
to receipt of a non-study 
primary series or first booster 
COVID-19 vaccine in addition 
to participants who withdraw 
consent.  
To clarify statements to 
cover both types of 
participant withdrawal. 
Section 6.4.3 (Concomitant 
Medications and Vaccines That May 
Lead to the Elimination of a 
Participant from Per-protocol 
Analyses) 
Clarified that any non-study 
COVID-19 may lead to 
exclusion from the 
per-protocol analysis in 
addition to withdrawal from 
the study (for primary series or 
first booster only). 
To remain consistent with 
Section 7.3.1 (Participant 
Withdrawal). 
Section 7.1 (Criteria for Delay of 
Study Treatment) 
Additional criteria for delay of 
study treatment added for 
Part C, including seasonal 
influenza vaccine and 
diagnosed COVID-19. 
To allow rescheduling of IP 
dosing in specified 
situations. 
Section 8.1.3 (Convalescent Period 
Starting With the Illness Visit), 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 19) 
Text added to allow 
participants who have been 
asymptomatic for more than 
72 hours prior to Day 14 to 
reduce the frequency of 
telemedicine calls during the 
convalescent period.  
To provide a reduced 
telemedicine call burden for 
the sites and participants 
when certain criteria are 
met. 
Section 9.5.2 (Safety Analyses, Table 
12) 
Added “Part A” to the table 
title. 
To clarify that this section 
applies to Part A of the 
study. 
Section 9.5.4 (Exploratory Analyses in 
Part A) 
Added “in Part A” to the 
section title and removed 
section paragraph specific to 
Part A, as this is now specified 
in the title. 
To clarify that this section 
applies to Part A of the 
study. 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 17 and Table 18) 
Duration of eDiary collection 
was corrected to Day 759. 
The eDiary collection 
duration was incorrectly 
listed in the previous version 
of the schedules of events. 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 18) 
Window for safety calls was 
increased from ±3 days to ±7 
days. 
The safety call window was 
increased to allow flexibility 
for sites and participants. 

ModernaTX, Inc. 
07 Apr 2022 
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Section # and Name 
Description of Change 
Brief Rationale 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 18) 
Window for Day 759 Visit 
was changed from ±14 days to 
-14/+28 days. 
The visit window was 
increased to allow flexibility 
for the sites and participants. 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 23) 
Window for BD-3 Visit 
changed from -3/+14 to ±14 
days. 
The visit window was 
increased to allow flexibility 
for the sites and participants. 
Section 11.1 (Appendix 1: Schedules 
of Events, Table 23) 
Clarified that not all 
participants may receive the 
booster in Part C; added 
footnote 4 regarding sample 
collection details for blood for 
immunologic analysis; 
clarified that physical 
examinations and vital sign 
collection are optional for 
participants who chose not to 
receive a BD. Clarified that 
pregnancy tests at the BD-1 
visit are for participants who 
receive a BD. 
Text added for clarity. 
Section 11.2.6 (Informed Consent 
Process) 
Clarified that participants who 
are rescreened or rescheduled 
are not required to re-sign the 
same version of the ICF if 
occurring within 28 days from 
the previous ICF signature 
date. 
Text added for clarity. 
Section 11.5 (Appendix 5: Adverse 
Events of Special Interest Terms) 
Appendix updated to clarify 
AESI terms.  
Text edited for clarity.  

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
mRNA-1273 
 
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IRB and Regulatory Authority Approval 
A copy of this amended protocol will be sent to the IRB and regulatory authority. 
The changes described in this amended protocol require IRB approval prior to implementation. In 
addition, if the changes herein affect the informed consent, sites are required to update and submit 
a revised informed consent for approval that incorporates the changes described in this amended 
protocol. 

ModernaTX, Inc. 
07 Apr 2022 
Protocol mRNA-1273-P301, Amendment 10 
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1. 
PROTOCOL SUMMARY 
1.1. 
Synopsis 
Protocol Number: 
mRNA-1273-P301 
Title: 
A 
Phase 
3, 
Randomized, 
Stratified, 
Observer-Blind, 
Placebo-Controlled Study to Evaluate the Efficacy, Safety, and 
Immunogenicity of mRNA-1273 SARS-CoV-2 Vaccine in Adults 
Aged 18 Years and Older. 
Study Phase: 
3 
Objectives: 
Primary: 
• To demonstrate the efficacy of mRNA-1273 to prevent 
coronavirus disease 2019 (COVID-19). 
• To evaluate the safety and reactogenicity of 2 injections of 
mRNA-1273 given 28 days apart. 
Secondary: 
• To evaluate the efficacy of mRNA-1273 to prevent severe 
COVID-19. 
• To evaluate the efficacy of mRNA-1273 to prevent 
serologically confirmed severe acute respiratory syndrome 
coronavirus 2 
(SARS-CoV-2) 
infection 
or 
COVID-19 
regardless of symptomatology or severity. 
• To evaluate vaccine efficacy (VE) against a secondary 
definition of COVID-19. 
• To evaluate VE to prevent death caused by COVID-19. 
• To evaluate the efficacy of mRNA-1273 to prevent COVID-19 
after the first dose of investigational product (IP). 
• To evaluate the efficacy of mRNA-1273 to prevent COVID-19 
in all study participants, regardless of evidence of prior 
SARS-CoV-2 infection. 
• To evaluate the efficacy of mRNA-1273 to prevent 
asymptomatic SARS-CoV-2 infection. 

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Exploratory for Part A: 
• To evaluate the effect of mRNA-1273 on the viral infection 
kinetics as measured by viral load at SARS-CoV-2 infection 
diagnosis by reverse transcriptase polymerase chain reaction 
(RT-PCR) and number of days from the estimated date of 
SARS-CoV-2 infection until undetectable SARS-CoV-2 
infection by RT-PCR. 
• To assess VE to reduce the duration of symptoms of 
COVID-19. 
• To evaluate VE against all-cause mortality. 
• To assess VE against burden of disease due to COVID-19. 
• To evaluate the genetic and/or phenotypic relationships of 
isolated SARS-CoV-2 strains to the vaccine sequence. 
• To evaluate immune response markers after dosing with IP as 
correlates of risk of COVID-19 and as correlates of risk of 
SARS-CoV-2 infection. 
• To conduct additional analyses related to furthering the 
understanding of SARS-CoV-2 infection and COVID-19, 
including analyses related to the immunology of this or other 
vaccines, detection of viral infection, and clinical conduct.  
Exploratory for Part C: 
• To evaluate the safety of a booster dose (BD) of mRNA-1273 
• To evaluate the immunogenicity of a BD of mRNA-1273. 
Study Design and 
Methodology: 
This is a 3-part Phase 3 study, comprising Part A, Part B, and Part C 
(Figure 1). Participants in Part A, the Blinded Phase of this study, 
were blinded to their treatment assignment. Given that the primary 
efficacy endpoint for mRNA-1273 against COVID-19 was met per 
the protocol-defined interim analysis (IA), Part B, the Open-Label 
Observational Phase of this study, was designed to offer participants 
who received placebo in Part A of this study an option to request 
open-label mRNA-1273 while investigational vaccine was still 
available. With regard to eligibility for Part B, the US Centers for 
Disease Control (CDC)-Emergency Use Authorization (EUA) 
guidance specifications will supersede eligibility criteria in the 
protocol. Part C is designed to offer eligible participants in Part B the 
option to request a BD of mRNA-1273. With regard to eligibility for 
Part C, the CDC-EUA guidance specifications will supersede 
eligibility criteria in the protocol. 

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Part A, the Blinded Phase: 
The Blinded Phase of this study (Figure 1) is a randomized, stratified, 
observer-blind, placebo-controlled evaluation of the efficacy, safety, 
and immunogenicity of mRNA-1273 SARS-CoV-2 vaccine 
compared to placebo in adults 18 years of age and older who have no 
known history of SARS-CoV-2 infection but whose locations or 
circumstances put them at appreciable risk of acquiring COVID-19 
and/or SARS-CoV-2 infection. 
Participants will be randomly assigned to receive injections of either 
100 µg of mRNA-1273 vaccine or a placebo control in a 
1:1 randomization ratio. Assignment will be stratified by age and 
health risk. This is a case-driven study and thus final sample size of 
the study will depend on the actual attack rate of COVID-19. 
All participants will be assessed for efficacy and safety endpoints and 
provide a nasopharyngeal (NP) swab sample and blood sample before 
the first and second dose of IP, in addition to a series of post-dose 
blood samples for immunogenicity through 24 months after the 
second dose of IP. Efficacy assessments will include surveillance for 
COVID-19 with RT-PCR confirmation of SARS-CoV-2 infection 
after the first and second dose of IP. 
As noted above, this is a case-driven study: if the prespecified criteria 
for early efficacy are met at the time of either IA or overall efficacy 
at the primary analysis, a final study report describing the efficacy 
and safety of mRNA-1273 will be prepared based on the data 
available at that time. In the event that success criteria are met either 
at the time of the IA or when the total number of cases toward the 
primary endpoint have accrued, participants will continue to be 
followed in a blinded fashion until Month 25 to enable assessment of 
long-term safety and durability of VE. 
If the study concludes early, all participants will be requested to 
provide a final blood sample at the time of study conclusion. 
Each participant will receive 2 doses of IP by 0.5 mL intramuscular 
(IM) injection, the first on Day 1 and the second on Day 29. An NP 
swab sample will be collected prior to the first and second dose of IP, 
for evaluation by RT-PCR. Participants will be given an electronic 
diary (eDiary) to report solicited adverse reactions (ARs) for 7 days 
after each dose of IP and to prompt an unscheduled clinic visit for 
clinical evaluation and NP swab sample if a participant experiences 
any symptoms of COVID-19 (throughout study). All participants will 
receive safety calls on Day 8, Day 15, Day 22, Day 36, and Day 43 

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that will serve both to monitor for unsolicited adverse events (AEs) 
and to monitor for symptoms of COVID-19. 
Surveillance for COVID-19 will be performed through weekly 
contacts with the participant via a combination of telephone calls and 
completion of an eDiary starting at Day 1 through the end of the 
study. 
Participants with symptoms of COVID-19 lasting at least 48 hours 
(except for fever and/or respiratory symptoms) will return to the 
clinic or will be visited at home by medically qualified site staff 
within 72 hours (an “Illness Visit”) to collect an NP swab sample for 
RT-PCR testing for SARS-CoV-2 and other respiratory pathogens, or 
alternatively, if a clinic or home visit is not possible, will submit a 
saliva sample for SARS-CoV-2 RT-PCR testing. Any confirmed 
COVID-19 occurring in a participant will be captured as a medically 
attended AE (MAAE) along with relevant concomitant medications 
and details about severity, seriousness, and outcome. All confirmed 
serious COVID-19 cases will be reported to the Sponsor or designee 
within 24 hours. 
Starting with the Illness Visit, study participants will be monitored by 
the study investigator (or appropriately delegated study staff) for a 
14-day period (from the Illness Visit or initial COVID-19 contact) or 
until symptoms resolve, whichever is later, and which may include 
symptoms persisting longer than the 28-day Convalescent Period. 
Each participant diagnosed with COVID-19 will monitor their body 
temperature, oxygen saturation, and symptoms following the 
diagnosis of COVID-19. In addition to daily follow-up of symptoms, 
assessments will include the collection of saliva samples during the 
28-day period following the diagnosis of SARS-CoV-2 infection. The 
investigator will determine if medical attention is required due to 
worsening of COVID-19. Finally, a Convalescent Visit will be 
scheduled approximately 28 days after the initial Illness Visit. At this 
visit, a saliva sample will be collected, and a blood sample will be 
drawn for immunologic assessment of SARS-CoV-2 infection. 
The 28-day period following the Illness Visit is referred to as the 
Convalescent Period. If during the Convalescent Period the 
participant has a positive result for SARS-CoV-2 from the Illness 
Visit, the participant will continue the Convalescent Period. If the 
participant has a negative result for SARS-CoV-2 from the Illness 
Visit, the participant will exit the Convalescent Period, including 

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discontinuation of daily telemedicine visits and collection of saliva 
samples, and will return to their respective study schedule. 
At each dosing visit, participants will be instructed (Day 1) or 
reminded (Day 29) on how to document and report solicited ARs in 
the eDiary provided. Solicited ARs will be assessed for 7 days after 
each IP dose and unsolicited AEs will be assessed for 28 days after 
each IP dose; serious AEs (SAEs), MAAEs, AEs leading to 
withdrawal, will be assessed throughout the study. 
Part B, the Open-Label Observational Phase: 
Part B, the Open-Label Observational Phase of the study, is prompted 
by the authorization of a COVID-19 vaccine under EUA. 
Transitioning the study to Part B permits all ongoing study 
participants to be informed of the availability and eligibility criteria 
of any COVID-19 vaccine made available under an EUA and the 
option to offer all ongoing study participants who request unblinding, 
an opportunity to schedule a participant decision visit (PDV) at the 
study site to learn their original treatment assignment (placebo vs. 
mRNA-1273 vaccine).  
Part B, the Open-Label Observational Phase of the study, also 
provides the opportunity for eligible study participants who 
previously received placebo to actively request to receive 2 doses of 
mRNA-1273 vaccine (subject to investigational vaccine availability).  
All study participants will receive a notification letter and will be 
asked to schedule a PDV. Principal Investigators should consider 
current local public health guidance for administration of COVID-19 
vaccines under EUA when determining the scheduling priority of 
participants. 
All participants will proceed to Part B, the Open-Label Observational 
Phase of the study, starting with a PDV (Figure 2).  

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At the PDV, all participants will: 
• Be encouraged to remain in the ongoing study, 
• Be given the option to be unblinded as to their original group 
assignment (placebo vs. mRNA-1273 vaccine), 
• Be counselled about the importance of continuing other public 
health measures to limit the spread of disease including social 
distancing, wearing a mask, and hand-washing, 
• Sign a revised informed consent form (ICF), 
• Provide a NP swab for RT-PCR for SARS-CoV-2 and a blood 
sample for serology prior to unblinding.  
The following participants will continue with the original study 
Schedule of Events (SoEs) (Figure 2): 
• Participants who request to not be unblinded, 
• Participants who request to be unblinded and received 
mRNA-1273, and 
• Participants who request to be unblinded and received placebo 
and choose to remain on placebo. 
Participants who are unblinded, received placebo, are eligible, and 
request to receive mRNA-1273 (Figure 2) will have the following 
clinic visits:  
• Open-label Dose 1 (OL-D1): To occur at the PDV or at a 
scheduled subsequent visit. 
• Open-label Dose 2 (OL-D29): To occur 28 days after Dose 1 
on OL-D1. 
• Open-label Clinic Visit (OL-D57): To occur 1 month after 
Dose 2 on OL-D29. 
• In addition, participants will continue to comply with the 
Original Study SoEs, as applicable. 
Participants who are unblinded, received ONLY 1 dose of 
mRNA-1273, are eligible, and request to receive mRNA-1273 
(Figure 2) will have the following clinic visits: 
• Their second dose on OL-D1: To occur at the PDV or at a 
scheduled subsequent visit. 
• And return on OL-D29: To occur 1 month after Dose 2 on 
OL-D1.  

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• In addition, participants will continue to comply with the 
Original Study SoEs, as applicable. 
All participants remain on their original SoE to complete 24 months 
of follow-up after Dose 2; study participants who enter the 
Supplemental/Modified Supplemental SoE as described above do so 
in addition to their original SoE. Accordingly, all study participants 
will complete the full study follow-up to 24 months after the second 
dose of their original inoculation (mRNA-1273 or placebo), or 
25 months after the first dose if the second dose is missed. 
At a point when the mRNA-1273 vaccine is no longer available for 
study use, any participant who schedules a PDV after this timepoint 
will be unblinded (with no option to stay blinded) but will not be 
offered to receive mRNA-1273 study vaccine. These participants will 
have all of the same procedures performed as outlined in the SoE 
table, with the exception of being offered to receive mRNA-1273 
vaccine. 
After the Biologics License Application database lock (on 
04 May 2021), any remaining participants who had not been 
unblinded were unblinded by the Moderna study team and received 
their unblinding treatment assignment (placebo vs. messenger RNA 
[mRNA] vaccine) via certified letter from the study site. 
Part C, the Booster Dose Phase 
Part C, providing a BD for all eligible participants who choose to 
receive one, is prompted by the interim results of an ongoing 
Moderna Phase 2a study (mRNA-1273-P201; NCT04405076), in 
which participants who, 6 to 8 months prior, received 2 doses of 
50 µg or 100 µg of mRNA-1273 were administered a 50 µg booster 
of mRNA-1273. Results demonstrated enhanced immune responses 
compared to pre-boost levels and met the noninferiority criteria 
stipulated in the Food and Drug Administration Guidance on EUA 
for Vaccines to Prevent COVID-19. In addition, no new safety 
signals emerged upon administration of the BD in 
Study mRNA-1273-P201. Based on cumulative evidence, the 
benefit-risk profile of a BD of mRNA-1273 is favorable, particularly 
in light of increasing breakthrough disease with the emergence of 
variants. With the wider availability of boosters under EUA, 
providing the option for a BD to all eligible participants currently 
enrolled in Part B is expected to promote retention of participants in 
the ongoing study and thereby defend the scientific integrity of the 

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study for the planned 2-year duration of follow-up after the 
completion of the primary vaccination series regimen. 
Each study participant will receive a notification letter and will be 
asked to schedule a BD-1 visit at their study site. Principal 
Investigators should consider current local public health guidance for 
administration of COVID-19 vaccines under EUA and marketing 
authorization (if any) when determining the scheduling priority of 
participants.  
At the BD-1 visit, each participant will: 
• Be encouraged to remain in the ongoing study, 
• Sign a revised ICF that includes both updated safety 
information relevant to the ongoing study and a BD, and the 
option to receive a BD, 
• Be given the option to receive a BD consisting of a 50 µg 
dose of mRNA-1273, 
• Be counselled about the importance of continuing other 
public health measures to limit the spread of disease including 
social distancing, wearing a mask, and hand-washing. 
After the BD-1 visit, participants who do not receive a BD will 
continue with the Part C Supplemental SoE for the BD-2 and BD-3 
visits but will not have the BD-1a visit or the safety calls. 
Participants who request a BD and are eligible  and have no 
contraindications to further dosing will have the following study site 
visits and complete scheduled activities (subject to investigational 
vaccine availability) according to the Part C Supplemental SoE: 
• BD-1 visit: Participants will receive a single 50 µg dose of 
mRNA-1273. 
• BD-1a visit: Optional, and subject to blood sample kit 
availability, Day 4, 3 days after BD on Day 1. 
• BD-2 visit: Day 29, 28 days after the BD on Day 1. 
• BD-3 visit: Day 181, 180 days after the BD on Day 1. 
The investigator is responsible for conducting all assessments as 
specified in the Part C Supplemental SoE, according to the schedule. 
As this Supplemental SoE is intended to occur in addition to the 
original SoEs being followed by all participants in Part B, there is a 
possibility for study visits to overlap. If visits overlap according to 

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respective visit windows, a single visit may be done with the 
combined study procedures completed once.  
This study will be conducted in compliance with the protocol, Good 
Clinical Practice, and all applicable regulatory requirements. 
Randomization: 
In Part A, the Blinded Phase of the study, approximately 
30,000 participants will be randomly assigned in 1:1 ratio to receive 
either mRNA-1273 100 µg or placebo. The randomization will be in 
a blinded manner using a centralized interactive response technology, 
in accordance with pre-generated randomization schedules. 
Stratification: 
Randomization in Part A, the Blinded Phase of the study, will be 
stratified based on age and, if they are < 65 years of age, based on the 
presence or absence of risk factors for severe illness from COVID-19 
based on CDC recommendation as of March 2020. There will be 
3 strata for randomization: ≥ 65 years, < 65 years and categorized to 
be at increased risk (“at risk”) for the complications of COVID-19, 
and < 65 years “not at risk”. Risk will be defined based on the study 
participants’ relevant past and current medical history. At least 25% 
of enrolled participants, up to 50%, will be either ≥ 65 years of age or 
< 65 years of age and “at risk” at Screening. 
Participants who are < 65 years old will be categorized as at risk for 
severe COVID-19 illness if they have at least 1 of the following risk 
factors at Screening: 
• Chronic lung disease (eg, emphysema and chronic bronchitis, 
idiopathic pulmonary fibrosis, and cystic fibrosis) or moderate 
to severe asthma 
• Significant cardiac disease (eg, heart failure, coronary artery 
disease, congenital heart disease, cardiomyopathies, and 
pulmonary hypertension) 
• Severe obesity (body mass index ≥ 40 kg/m2) 
• Diabetes (Type 1, Type 2, or gestational) 
• Liver disease 
• Human immunodeficiency virus infection 
Study 
Population: 
Participants (males and females 18 years of age or older at time of 
consent), who are at risk of SARS-CoV-2 infection with no known 
history of SARS-CoV-2 infection, are a subset of the planned target 
population. Additionally, potential study participants at increased risk 

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of complications from COVID-19 will be included, since it is 
hypothesized that these participants might derive the greatest benefit 
from a vaccine. Participants ≥ 65 years of age will be eligible for 
enrollment with or without underlying medical conditions further 
increasing their risk of severe COVID-19. 
Study sites may be selected based on SARS-CoV-2 infection risk of 
the local population. Approximately 30,000 participants will be 
enrolled. 
The full lists of inclusion and exclusion criteria are provided in the 
body of the protocol. 
Efficacy 
Assessments: 
Primary Efficacy Assessment: 
To be considered as a case of COVID-19 for the evaluation of the 
Primary Efficacy Endpoint, the following criteria must be met: 
• The participant must have experienced at least TWO of the 
following systemic symptoms: fever (≥ 38ºC), chills, myalgia, 
headache, sore throat, new olfactory and taste disorder(s), OR 
• The participant must have experienced at least ONE of the 
following respiratory signs/symptoms: cough, shortness of 
breath or difficulty breathing, OR clinical or radiographical 
evidence of pneumonia; AND 
• The participant must have at least 1 NP swab, or saliva 
sample (or respiratory sample, if hospitalized) positive for 
SARS-CoV-2 by RT-PCR. 
Secondary Efficacy Assessments: 
To be considered severe COVID-19, the following criteria must be 
met: a confirmed case of COVID-19 as per the Primary Efficacy 
Endpoint case definition, plus any of the following: 
• Clinical signs indicative of severe systemic illness, respiratory 
rate ≥ 30 per minute, heart rate ≥ 125 beats per minute, SpO2 
≤ 93% on room air at sea level or PaO2/FIO2 < 300 mmHg, 
OR 
• Respiratory failure or acute respiratory distress syndrome 
(defined as needing high-flow oxygen, non-invasive or 
mechanical ventilation, or extracorporeal membrane 
oxygenation), evidence of shock (systolic blood pressure [BP] 
< 90 mmHg, diastolic BP < 60 mmHg or requiring 
vasopressors), OR 
• Significant acute renal, hepatic, or neurologic dysfunction, 
OR 

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• Admission to an intensive care unit or death. 
The secondary case definition of COVID-19 is defined as having any 
of the following systemic symptoms: fever (temperature ≥ 38ºC) or 
chills, cough, shortness of breath or difficulty breathing, fatigue, 
muscle aches or body aches, headache, new loss of taste or smell, 
sore throat, nasal congestion or rhinorrhea, nausea or vomiting or 
diarrhea, AND a positive NP swab or saliva sample (or respiratory 
sample, if hospitalized) for SARS-CoV-2 by RT-PCR. 
Death attributed to COVID-19 is defined as any participant who dies 
during the study with a cause directly attributed to a complication of 
COVID-19. 
Asymptomatic SARS-CoV-2 infection is determined by 
seroconversion due to infection assessed by binding antibody (bAb) 
levels against SARS-CoV-2 as measured by a ligand-binding assay 
specific to the SARS-CoV-2 nucleocapsid protein and a negative NP 
swab sample for SARS-CoV-2 at Day 1.  
Immunogenicity 
Assessments: 
Immunogenicity assessments will include the following: 
• Serum bAb levels against SARS-CoV-2 as measured by 
ligand-binding assay specific to the SARS-CoV-2 S protein. 
• Serum bAb levels against SARS-CoV-2 as measured by 
ligand-binding assay specific to the SARS-CoV-2 
nucleocapsid protein. 
• Serum neutralizing antibody (nAb) titer against SARS-CoV-2 
as measured by pseudovirus and/or live virus neutralization 
assays. 
Safety 
Assessments: 
Safety assessments will include monitoring and recording of the 
following for each participant: 
• Solicited local and systemic ARs that occur during the 7 days 
following each injection (ie, the day of injection and 
6 subsequent days). Solicited ARs will be recorded daily using 
eDiaries (Part A). 
• Unsolicited AEs observed or reported during the 28 days 
following each injection (ie, the day of injection and 
27 subsequent days) (Part A [all participants] and Part C [only 
those who receive the BD]). 
• AEs leading to discontinuation from dosing and/or study 
participation from Day 1 through Day 759 or withdrawal from 
the study. 

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• MAAEs from Day 1 through Day 759 or withdrawal from the 
study. 
• SAEs from Day 1 through Day 759 or withdrawal from the 
study. 
• AEs of special interest (AESIs; for participants who receive the 
BD in Part C) from BD-Day 1 through Day 759 or withdrawal 
from the study. 
• Abnormal vital sign measurements. 
• Physical examination findings. 
• Pregnancy and accompanying outcomes. 
• Concomitant medications and non-study vaccinations. 

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Investigational 
Product, Dosage, 
and Route of 
Administration: 
The mRNA-1273 IP is a lipid nanoparticle (LNP) dispersion of an 
mRNA encoding the prefusion stabilized S protein of SARS-CoV-2 
formulated in LNPs composed of 4 lipids (1 proprietary and 
3 commercially available): the proprietary ionizable lipid SM-102; 
cholesterol; 1,2-distearoyl-sn-glycero-3 phosphocholine (DSPC); and 
1 monomethoxypolyethyleneglycol-2,3-dimyristylglycerol with 
polyethylene glycol of average molecular weight 2000 
(PEG2000-DMG). The mRNA-1273 vaccine is provided as a sterile 
liquid for injection and is a white to off- white dispersion in 
appearance, at a concentration of 0.2 mg/mL in 20 mM Tris buffer 
containing 87 mg/mL sucrose and 10.7 mM sodium acetate at pH 7.5. 
The placebo is 0.9% sodium chloride (normal saline) injection, which 
meets the criteria of the United States Pharmacopeia. 
In Part A and Part B, as applicable, IP will be administered as an IM 
injection into the deltoid muscle on a 2-dose injection schedule on 
Day 1 and Day 29. For injections administered for Part A and Part B, 
each injection will have a volume of 0.5 mL and contain 
mRNA-1273 100 µg or saline placebo. For Part C, each injection will 
have a volume of 0.25 mL and contain mRNA-1273 50 µg. 
Preferably, vaccine should be administered into the nondominant 
arm. The second dose of IP should be administered in the same arm 
as the first dose (Part A and Part B, as applicable). 
The IP will be prepared for injection as a single 0.5 mL (Part A and 
Part B) or 0.25 mL (Part C) dose for each participant per protocol, as 
detailed in the Pharmacy Manual. Unblinded personnel who will not 
participate in any other aspect of the study during Part A, the Blinded 
Phase, will perform IP accountability, dose preparation, and IP 
administration. Study site personnel who were blinded during the 
Blinded Phase will be unblinded at the participant level at the PDV. 
Sample Size: 
The sample size is driven by the total number of cases to demonstrate 
VE (mRNA-1273 vs. placebo) to prevent COVID-19 in Part A. 
Under the assumption of proportional hazards over time and with 
1:1 randomization of mRNA-1273 and placebo, a total of 
151 COVID-19 cases will provide 90% power to detect a 
60% reduction in hazard rate (60% VE), rejecting the null hypothesis 
H0: VE ≤ 30%, with 2 IAs at 35% and 70% of the target total number 
of cases using a 1-sided O’Brien-Fleming boundary for efficacy and 
a log-rank test statistic with a 1-sided false positive error rate of 
0.025. The total number of cases pertains to the Per-protocol (PP) Set 
accruing at least 14 days after the second dose. There are 2 planned 

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IAs in this study, which will be performed when approximately 35% 
and 70% of the target total number of cases have been observed. 
Approximately 30,000 participants will be randomized with the 
following assumptions: 
• The target VE against COVID-19 is 60% (with 
95% confidence interval [CI] lower bound ruling out 30%, 
rejecting the null hypothesis H0: VE ≤ 30%). 
• A 6-month COVID-19 incidence rate of 0.75% in the placebo 
arm. 
• An annual dropout rate of 2% (loss of evaluable participants). 
• Two IAs at 35% and 70% of total target cases across the 
2 treatment groups with O’Brien-Fleming boundaries for 
efficacy monitoring. 
• 3-month uniform accrual. 
• Approximately 15% of participants will be excluded from the 
PP population, and participants are at risk for COVID-19 
starting 14 days after the second dose. 
Power for Selected Secondary Efficacy Endpoints: 
For the secondary objective on VE against virologically confirmed 
SARS‑CoV‑2 infection or COVID‑19 regardless of symptomatology 
or severity (COV-INF), the study will have ≥ 90% power to 
demonstrate the VE is above 30% (to reject null hypothesis 
VE ≤ 30%) at 1-sided alpha of 2.5% if the true VE to prevent 
COV-INF is 60%, because every COVID-19 endpoint is necessarily 
a COV-INF endpoint. 
For the secondary objective on VE against severe COVID-19, the 
power of demonstrating VE based on a total of 30 and 60 events 
under different scenarios of true VE and VE criteria has been 
calculated. 

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Statistical 
Methods: 
Statistical Hypotheses: For the primary efficacy objective, the null 
hypothesis of this study is that the VE of mRNA-1273 to prevent first 
occurrence of COVID-19 is ≤ 30% (ie, H0efficacy: VE ≤ 0.3). 
The study will be considered to meet the primary efficacy objective if 
the corresponding CI of VE rules out 30% at either one of the IAs or 
at the primary analysis. In the primary analysis of VE of COVID-19, 
cases will be counted starting 14 days after the second dose of IP. 
Vaccine efficacy is defined as the percent reduction in the hazard of 
the primary endpoint (mRNA-1273 vs. placebo). Equivalently, the 
null hypothesis is: 
• H0efficacy: hazard ratio (HR) ≥ 0.7 (equivalently, proportional 
hazards VE ≤ 0.3). 
A stratified Cox proportional hazard model will be used to assess the 
magnitude of the treatment group difference (ie, HR) between 
mRNA-1273 and placebo at a 1-sided 0.025 significance level. 
Analysis Populations: Analysis populations for statistical analyses 
are Randomization Set, Full Analysis Set (FAS), Modified 
Intent-to-Treat (mITT) Set, PP Set, Immunogenicity Subset, Solicited 
Safety Set, and Safety Set, as shown below: 
• Randomization Set: All participants who are randomized, 
regardless of the participants’ treatment status in the study. 
• FAS: All randomized participants who received at least one dose 
of IP. Participants will be analyzed according to the group to 
which they were randomized. 
• mITT Set: All participants in the FAS who had no immunologic 
or virologic evidence of prior COVID-19 (ie, negative NP swab 
test at Day 1 and/or bAb against SARS-CoV-2 nucleocapsid 
below limit of detection or lower limit of quantification [LLOQ]) 
at Day 1 before the first dose of IP. Participants will be analyzed 
according to the group to which they were randomized. 
• PP Set: All participants in the mITT Set who received planned 
doses of IP per schedule and have no major protocol deviations, 
as determined and documented by Sponsor prior to database lock 
and unblinding, that impact critical or key study data. 
Participants will be analyzed according to the group to which 
they were randomized. 
• Immunogenicity Subset: All participants in the FAS who were 
sampled into subset for characterizing mRNA-1273 
immunogenicity and had a valid immunogenicity test result prior 

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to the first dose of IP and at least 1 valid result after the first dose 
of IP. Participants in the subset who had major protocol 
deviations that impact critical or key immunogenicity or study 
data may be excluded from the Immunogenicity Subset. The 
details of the Immunogenicity Subset will be documented prior 
to analysis of immunogenicity data.  
• Solicited Safety Set: The Solicited Safety Set consists of all 
randomized participants who received at least one dose of IP and 
contributed any solicited AR data. The Solicited Safety Set will 
be used for the analyses of solicited ARs and participants will be 
included in the treatment group corresponding to the IP that they 
actually received. 
• Safety Set : All randomized participants who received at least 
one dose of IP. The Safety Set will be used for all analyses of 
safety except for the solicited ARs. Participants will be included 
in the treatment group corresponding to the IP that they actually 
received. 
Efficacy Analyses: Efficacy analyses will be performed using the 
FAS, mITT, and PP populations, and participants will be included in 
the treatment group to which they were randomized. The primary 
analysis population for efficacy will be the PP Set. 
The table below summarizes the analysis approach for primary and 
secondary efficacy endpoints for Part A, the randomized, 
observer-blind, and placebo-controlled phase of the study. Sensitivity 
analysis methods are described for each endpoint as applicable.  

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Endpoint 
Statistical Analysis Methods 
Primary endpoint: 
VE of mRNA-1273 to 
prevent COVID-19 
• Primary analysis: VE will be 
estimated with 1 – HR (mRNA-
1273 vs. placebo) using a Cox 
proportional hazard regression 
model with treatment group as a 
fixed effect and adjusting for 
stratification factor based on the 
PP Set, with cases counted 
starting 14 days after the second 
dose of IP. 
• Analysis using the same model 
based on the mITT Set. 
• Sensitivity analysis using the 
same model based on the PP Set, 
with cases counted starting either 
immediately after the second 
dose of IP or immediately after 
the first dose of IP. 
• Subgroup analysis of the primary 
efficacy endpoint will be 
performed to assess consistency 
of VE, such as in the age groups 
≥ 18 and < 65 years and 
≥ 65 years. 
• Supportive analysis of VE to be 
estimated with 1 – ratio of 
incidence rates with 95% CI 
using the exact method 
conditional upon the total number 
of cases. 
• Supportive analysis of 
cumulative incidence VE.  
Secondary endpoints: 
• Vaccine efficacy of 
mRNA-1273 to prevent 
severe COVID-19 
• Vaccine efficacy of 
mRNA-1273 to prevent 
serologically 
Similar analysis method as for the 
primary endpoint analysis. 
For each of the secondary endpoints: 
• Primary analysis: VE will be 
estimated with 1 – HR 
(mRNA-1273 vs. placebo) 
using a Cox proportional 

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confirmed 
SARS‑CoV‑2 infection 
or COVID‑19 
regardless of 
symptomatology or 
severity. 
• Vaccine efficacy of 
mRNA-1273 to prevent 
COVID-19 using a 
secondary definition of 
symptoms 
• Vaccine efficacy of 
mRNA-1273 to prevent 
death caused by 
COVID-19 
• Vaccine efficacy of 
mRNA-1273 to prevent 
COVID-19 after the 
first dose of IP 
• Vaccine efficacy of 
mRNA-1273 to prevent 
asymptomatic 
SARS-CoV-2 infection 
hazard regression model with 
treatment group as a fixed 
effect and adjusting for 
stratification factor based on 
the PP Set, with cases 
counted starting 14 days after 
the second dose of IP. 
• Analysis using the same 
model based on the mITT Set. 
• Sensitivity analyses with 
cases counted starting 
immediately after the second 
dose of IP, 14 days after the 
first dose of IP, immediately 
after the first dose of IP, and 
immediately after 
randomization. 
• Vaccine efficacy and 95% CI 
based on the case incidence 
will be estimated with 1 – 
ratio of incidence rates using 
the exact method conditional 
upon the total number of 
cases. 
Vaccine efficacy of 
mRNA-1273 to prevent 
COVID-19 in all study 
participants, regardless of 
evidence of prior 
SARS-CoV-2 infection 
The FAS population will be used for 
this secondary objective, using 
similar analysis methods as for the 
primary endpoint analysis. 
• Primary analysis: VE will be 
estimated with 1 – HR 
(mRNA-1273 vs. placebo) 
using a Cox proportional 
hazard regression model with 
treatment group as a fixed 
effect and adjusting for 
stratification factor based on 
the FAS, with cases counted 
starting 14 days after the 
second dose of IP. 
• Sensitivity analyses with 
cases counted starting 

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immediately after the second 
dose of IP, 14 days after the 
first dose of IP, immediately 
after the first dose of IP, and 
immediately after 
randomization.  
 
The table below summarizes the analysis approach for long-term 
endpoints.  

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Endpoint 
Statistical Analysis Methods 
Long-term endpoints: 
Cases starting 14 days after 
the second injection of IP 
for participants in the 
mRNA-1273 Cohort and 
the Placebo Cohort, or 
after the second injection 
of mRNA-1273 for 
participants in the Placebo-
mRNA-1273 Cohort  
• COVID-19 
• Severe COVID-19 
• Either COVID-19 
or SARS-CoV-2 
infection 
• Secondary 
definition of 
COVID-19 
• Death caused by 
COVID-19 
• COVID-19 
regardless of 
evidence of prior 
SARS-CoV-2 
infection 
determined by 
serologic titer 
against 
SARS-CoV-2 
nucleocapsid 
Cases starting 14 days after 
the first injection of IP for 
participants in the 
mRNA-1273 Cohort and 
the Placebo Cohort, or 
after the first injection of 
mRNA-1273 for 
participants in the Placebo-
mRNA-1273 Cohort  
• Long-term efficacy will be 
evaluated after the primary 
analysis of the primary 
vaccination series with 
mRNA-1273 by including 
data collected in the 
Open-Label Phase. 
• Long-term efficacy data will 
be summarized descriptively 
by treatment cohort without 
cohort comparison. 
• In the primary approach, 
cases will be counted starting 
14 days after the second dose 
of IP for participants in 
treatment cohorts of mRNA-
1273 and placebo or starting 
14 days after the second dose 
of mRNA-1273 for 
participants in the 
Placebo-mRNA-1273 Cohort. 
• Sensitivity analyses with 
cases starting from the second 
dose, 14 days after the first 
dose, or first dose of IP for 
participants in the cohorts of 
mRNA-1273 and placebo, or 
mRNA-1273 for participants 
in the Placebo-mRNA-1273 
Cohort may be provided.  
• Incidences of cases assessed 
by numbers, rates, and 2-
sided 95% CI based on the 
exact method adjusting for 
person-time will be 
summarized by treatment 
cohort. 
• The Kaplan-Meier analysis 
will be used to estimate 
cumulative incidences of time 

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• COVID-19 
SARS-CoV-2 infection in 
the absence of symptoms 
defining COVID-19 
starting 14-days after the 
second injection of: 
• IP for participants 
in the mRNA-1273 
Cohort and the 
Placebo Cohort, or 
mRNA-1273 for 
participants in the 
Placebo-mRNA-
1273 Cohort 
to first cases by treatment 
cohort. 
• Long-term efficacy analysis 
will be performed using the 
PP Set and mITT Set. 
• Efficacy analyses of 
unblinded/open-label phase 
data collected in Part B will 
be provided, as measured by 
the incidence rate of COVID-
19 after the BD of mRNA-
1273. The details of analysis 
of long-term efficacy and 
open-label phase data (Part B 
and Part C) will be provided 
in the statistical analysis plan 
(SAP). 
 
Safety: Safety and reactogenicity will be assessed by clinical review 
of all relevant parameters. Safety analyses will be provided for 
Parts A, B, and C separately unless specified otherwise. 
All safety analyses will be based on the Safety Set, except summaries 
of solicited ARs, which will be based on the Solicited Safety Set. All 
safety analyses will be provided by treatment group, and by treatment 
cohort as applicable, unless otherwise specified. 
The number and percentage of participants with any solicited local 
AR, with any solicited systemic AR, and with any solicited AR 
during the 7-day follow-up period after each injection will be 
provided only for Part A. A 2-sided 95% exact CI using the 
Clopper-Pearson method will be also provided for the percentage of 
participants with any solicited AR for each treatment group. Analysis 
of solicited AR will be provided using the Solicited Safety Set for 
Part A. 
The number and percentage of participants with unsolicited AEs 
(Part A [all participants] and Part C [only those who receive the 
BD]), SAEs, MAAEs, AESIs (Part C [only those who receive the 
BD]), and AEs leading to discontinuation from IP or withdrawal from 
the study will be summarized. Unsolicited AEs will be presented by 
Medical Dictionary for Regulatory Activities preferred term and 
system organ class. Analyses of AEs will be provided for Part A and 

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Part B using the Safety Set. For Part C, analysis of AEs will be 
provided in the Part C Safety Set (ie, participants who received 
booster in Part C). 
For all other safety parameters, descriptive summary statistics will be 
provided. 
Further details will be described in the SAP. 
Immunogenicity: The secondary immunogenicity endpoints will be 
analyzed using the Immunogenicity Subset by treatment group, by 
treatment cohort as applicable, and by baseline SARS-CoV-2 
serostatus, unless otherwise specified. 
The SAP will describe the complete set of immunogenicity analyses, 
including the approach to sample individuals into an Immunogenicity 
Subset for characterizing vaccine immunogenicity and assessing 
immunological correlates of risk and protection. 
Part A 
Data from quantitative immunogenicity assays will be summarized 
for each treatment group using positive response rates and geometric 
means with 95% CI, for each timepoint for which an assessment is 
performed. Data from qualitative (ie, yielding a positive or negative 
result) assays will be summarized by tabulating the frequency of 
positive responses for each assay by group at each timepoint that an 
assessment is performed. Analyses will focus on the 2 key 
immunogenicity timepoints and the change in marker response 
between them: Day 1 before the first dose of IP and Day 57 (28 days 
after the second dose of IP). The SAP will describe the complete set 
of immunogenicity analyses. 
Quantitative levels or geometric mean titer (GMT) of specific bAb 
with corresponding 95% CI at each timepoint and geometric mean 
fold rise (GMFR) of specific bAb with corresponding 95% CI at each 
postbaseline timepoint over pre-dose baseline at Day 1 will be 
provided by study arm. Descriptive summary statistics including 
median, minimum, and maximum will also be provided. 
The GMT of specific nAb with corresponding 95% CI at each 
timepoint and GMFR of specific nAb with corresponding 95% CI at 
each post-baseline timepoint over pre-dose baseline at Day 1 will be 
provided by study arm. Descriptive summary statistics including 
median, minimum, and maximum will also be provided. For 
summarizations of group variables values, antibody (Ab) values 
reported as below the LLOQ will be replaced by 0.5 × LLOQ. Values 

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that are reported as greater than the upper limit of quantification 
(ULOQ) without the actual values will be converted to the ULOQ. 
The number and percentage of participants with a fold rise ≥ 2, ≥ 3, 
and ≥ 4 of serum SARS-CoV-2-specific nAb titers and participants 
with seroresponse from baseline will be provided with 2-sided 95% 
CI using the Clopper-Pearson method at each post-baseline 
timepoint. Seroresponse at a participant level may be defined as a 
change from below the LLOQ to at least 4 times the LLOQ, or at 
least a 4-fold rise in nAb or vaccine antigen-specific bAb in 
participants with pre-existing nAb or bAb of at least the LLOQ at 
baseline/pre-vaccination. Seroresponse may also be defined for each 
specific assay assessing nAb or bAb. The definition of seroresponse 
will be finalized and documented in the SAP.  
The GMT of specific nAb for each group and the geometric mean 
ratio (GMR) of mRNA-1273 versus placebo in Part A with 
corresponding 2-sided 95% CI will be estimated at each study 
timepoint using an analysis of covariance model with the treatment 
group and baseline values, if applicable, as explanatory variables, the 
analysis may adjust for the stratification factor. 
Part C 
In Part C, the immunogenicity analysis of BD vaccine response will 
be performed using the noninferiority tests of the 2 null hypotheses 
based on the 2 key secondary endpoints, respectively. 
Part C Key Secondary Endpoint 1: Ab GMT at BD-Day 29 
Hypothesis: immunogenicity response to mRNA-1273 BD as 
measured by Ab GMT at BD-Day 29 in Part C is noninferior 
compared with Ab GMT at Day 57 (28 days after the second dose) in 
the primary series of mRNA-1273. 
The noninferiority of post-booster GMT at BD-Day 29 in Part C as 
compared to the primary series at Day 57 is considered to be 
demonstrated if the lower bound of the 95% CI of the GMR (ratio of 
GMT at BD-Day 29 vs. GMT at Day 57 [28 days after Dose 2 of the 
primary series]) is ≥ 0.67 using a noninferiority margin of 1.5 
(1.5-fold immuno-bridging margin for the lower bound of the 95% CI 
for GMT ratio/GMR). 
The GMT with 95% CI will be summarized using t-distribution of the 
log transferred values and then back transformed to the original scale. 
The GMR with 95% CI to compare post-booster GMT at BD-Day 29 
in Part C with the primary series GMT at Day 57 (28 days after the 

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second dose) will be computed based on the t-distribution of mean 
difference in the log transferred values and then back transformed to 
the original scale. 
Part C Key Secondary Endpoint 2: Ab Seroresponse Rate at 
BD-Day 29 
Hypothesis: immunogenicity response to mRNA-1273 BD as 
measured by seroresponse rate (SRR) at BD-Day 29 in Part C is 
noninferior compared with SRR of the primary series at Day 57 
(28 days after the second dose of the primary series of mRNA-1273). 
The noninferiority in SRR post-booster at BD-Day 29 in Part C 
compared with SRR of the primary series at Day 57 (28 days after the 
second dose of the primary series of mRNA-1273) is considered to be 
demonstrated if the lower bound of the 95% CI of the SRR difference 
(SRR of the booster at BD-Day 29 – SRR of the primary series at 
Day 57) is > -10% (using the noninferiority margin of 10%). The 
SRR difference is defined as the seroresponse rate at BD-Day 29 in 
Part C minus the seroresponse rate at Day 57 (28 days after the 
second dose) following the primary series of mRNA-1273. The 
seroresponse of a booster or the primary series is defined as a titer 
change from baseline (pre-Dose 1 in primary series) below the LLOQ 
to ≥ 4 × LLOQ, or at least a 4-fold rise if baseline is ≥ LLOQ. 
The SRR with 95% CI (using Clopper-Pearson method) will be 
provided. The SRR difference with 95% CI to compare post-booster 
SRR at BD-Day 29 in Part C with the primary series SRR at Day 57 
(28 days after the second dose) will be computed. The method for 
computing 95% CI of seroresponse rate difference will be provided 
in the SAP. 
The primary immunogenicity objective in Part C is met if 
noninferiority is demonstrated based on both key secondary 
endpoints (both GMT and SRR). 

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1.2. 
Schema 
Figure 1: 
Study Flow Diagram: Part A, the Blinded Phase Followed by Part B, the 
Open-Label Phase Including Part C, the Booster Dose Phase 
 
Abbreviations: BD = booster dose visit; EUA = emergency use authorization 
 

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Figure 2: 
Part B, the Open-Label Observational Phase, and Part C, the Booster Dose 
Phase 
 
a All participants are encouraged to remain in the study. 
b All participants are given the option to be unblinded to treatment received in Part A: Blinded Phase. 
c All participants are counselled about the importance of continuing other public health measures to limit the spread 
of disease including physical-social distancing, wearing a mask, and hand-washing. 
d All participants sign a revised informed consent form. 
e All participants consent to provide a nasopharyngeal swab and a blood sample for immunologic analysis. 
f mRNA-1273 recipients who only received 1 dose of the mRNA-1273 vaccine will receive the second dose of 
mRNA-1273 vaccine. Additional details provided in the Supplemental Schedule of Events (Table 22). 
g Placebo recipients who request to receive mRNA-1273 and meet eligibility will comply with a Supplemental 
Schedule of Events (Table 21) in addition to the Original Study Schedule of Events. 
h Original Study Schedule of Events (Table 16, Table 17, Table 18, and Table 19). 
i Procedures required or not required based on receipt of the booster dose are clarified in the Part C Supplemental 
Schedule of Events (Table 23).  
 

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TABLE OF CONTENTS 
Clinical Study Protocol ................................................................................................................1 
Declaration of Investigator ...........................................................................................................4 
Protocol Amendment Summary of Changes ................................................................................5 
IRB and Regulatory Authority Approval ...................................................................................10 
1. 
Protocol Summary .......................................................................................................11 
1.1. 
Synopsis .......................................................................................................................11 
1.2. 
Schema .........................................................................................................................35 
Table of Contents .......................................................................................................................37 
List of Tables ..............................................................................................................................42 
List of Figures ............................................................................................................................43 
List of Abbreviations ..................................................................................................................44 
2. 
Introduction ..................................................................................................................47 
2.1. 
Study Rationale ............................................................................................................47 
2.2. 
Background and Overview ..........................................................................................47 
2.2.1. 
Nonclinical Studies ..............................................................................................48 
2.2.2. 
Clinical Studies ....................................................................................................48 
2.3. 
Benefit/Risk Assessment .............................................................................................51 
2.3.1. 
Potential Benefits of Study Participation .............................................................51 
2.3.2. 
Risks From Study Participation ...........................................................................51 
2.3.3. 
Overall Benefit/Risk Conclusion .........................................................................53 
3. 
Objectives and Endpoints ............................................................................................54 
4. 
Study Design ................................................................................................................59 
4.1. 
General Design ............................................................................................................59 
4.1.1. 
Part A, the Blinded Phase .....................................................................................59 
4.1.2. 
Part B, the Open-Label Observational Phase .......................................................61 
4.1.3. 
Part C, the Booster Dose Phase ............................................................................64 
4.2. 
Scientific Rationale for Study Design .........................................................................65 
4.3. 
Choice of Dose and Control Product ...........................................................................66 
4.4. 
End of Study Definition ...............................................................................................66 
5. 
Study Population ..........................................................................................................68 
5.1. 
Inclusion and Exclusion Criteria (Part A, Part B, and Part C) ....................................68 
5.1.1. 
Inclusion Criteria ..................................................................................................68 
5.1.2. 
Exclusion Criteria .................................................................................................69 

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5.2. 
Participant Restrictions ................................................................................................71 
5.3. 
Screen Failures (Part A, Blinded Phase Only).............................................................71 
6. 
Study Treatment ...........................................................................................................72 
6.1. 
Investigational Product ................................................................................................72 
6.2. 
Dosing and Management of Investigational Product...................................................72 
6.2.1. 
Method of Randomly Assigning Participants to Treatment Groups (Part A, 
Blinded Phase Only).............................................................................................72 
6.2.2. 
Administration of Investigational Product ...........................................................73 
6.2.3. 
Delivery and Receipt ............................................................................................74 
6.2.4. 
Packaging and Labeling .......................................................................................74 
6.2.5. 
Storage ..................................................................................................................75 
6.2.6. 
Investigational Product Accountability ................................................................75 
6.2.7. 
Handling and Disposal .........................................................................................75 
6.2.8. 
Unblinding ............................................................................................................76 
6.3. 
Study Treatment Compliance ......................................................................................78 
6.4. 
Prior and Concomitant Therapy...................................................................................79 
6.4.1. 
Prior Medications and Therapies ...........................................................................79 
6.4.2. 
Concomitant Medications and Therapies .............................................................79 
6.4.3. 
Concomitant Medications and Vaccines That May Lead to the Elimination of 
a Participant From Per-protocol Analyses .............................................................80 
7. 
Delaying or Discontinuing Study Treatment and Participant Withdrawal from the 
Study ............................................................................................................................81 
7.1. 
Criteria for Delay of Study Treatment .........................................................................81 
7.2. 
Discontinuation of Study Treatment ............................................................................82 
7.3. 
Participant Withdrawal From the Study ......................................................................83 
7.3.1. 
Participant Withdrawal .........................................................................................83 
7.4. 
Lost to Follow-up ........................................................................................................84 
8. 
Study Assessments and Procedures .............................................................................86 
8.1. 
Efficacy and Immunogenicity Assessments and Procedures .......................................87 
8.1.1. 
Efficacy Assessments Related to COVID-19 and SARS-CoV-2 Infection .........87 
8.1.2. 
Surveillance for COVID-19 Symptoms ...............................................................88 
8.1.3. 
Convalescent Period Starting With the Illness Visit ............................................91 
8.1.4. 
Ancillary Supplies for Participant Use .................................................................93 

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8.1.5. 
Immunogenicity Assessments ..............................................................................94 
8.2. 
Safety Assessments ......................................................................................................94 
8.2.1. 
Safety Phone Calls ...............................................................................................95 
8.2.2. 
Use of Electronic Diaries .....................................................................................95 
8.2.3. 
Demographics/Medical History ...........................................................................98 
8.2.4. 
Physical Examination ...........................................................................................98 
8.2.5. 
Vital Sign Measurements .....................................................................................98 
8.2.6. 
Blood Sampling ....................................................................................................99 
8.3. 
Safety Definitions and Procedures.............................................................................100 
8.3.1. 
Adverse Event ....................................................................................................100 
8.3.2. 
Medically Attended Adverse Events ..................................................................100 
8.3.3. 
Adverse Events of Special Interest.....................................................................101 
8.3.4. 
Serious Adverse Events ......................................................................................104 
8.3.5. 
Solicited Adverse Reactions (Part A).................................................................105 
8.3.6. 
Recording and Follow-up of Pregnancy.............................................................108 
8.3.7. 
Recording and Follow-up of an AE and/or SAE................................................109 
8.3.8. 
Time Period and Frequency for Collecting AE and SAE Information ..............109 
8.3.9. 
Assessment of Intensity ......................................................................................109 
8.3.10. 
Assessment of Causality.....................................................................................110 
8.3.11. 
Reporting Adverse Events ..................................................................................111 
8.3.12. 
Regulatory Reporting Requirements for SAEs ..................................................111 
8.4. 
Monitoring Committees .............................................................................................112 
8.4.1. 
Protocol Safety Review Team ............................................................................112 
8.4.2. 
Data and Safety Monitoring Board ....................................................................112 
8.4.3. 
Adjudication Committee ....................................................................................113 
8.4.4. 
Independent Cardiac Event Adjudication Committee ........................................113 
8.5. 
Management of Overdose ..........................................................................................114 
8.6. 
Pharmacokinetics .......................................................................................................114 
8.7. 
Pharmacodynamics ....................................................................................................114 
8.8. 
Exploratory Assessments and Biomarkers ................................................................114 
8.9. 
Medical Resource Utilization and Health Economics ...............................................114 
9. 
Statistical Considerations ...........................................................................................115 

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9.1. 
Blinding and Responsibility for Analyses .................................................................115 
9.2. 
Statistical Hypotheses ................................................................................................115 
9.3. 
Sample Size Determination .......................................................................................116 
9.3.1. 
Power for Selected Secondary Efficacy Endpoints ............................................118 
9.4. 
Analysis Populations .................................................................................................119 
9.5. 
Statistical Analyses ....................................................................................................120 
9.5.1. 
Efficacy Analyses ...............................................................................................120 
9.5.2. 
Safety Analyses ..................................................................................................126 
9.5.3. 
Immunogenicity Analyses ..................................................................................127 
9.5.4. 
Exploratory Analyses in Part A ..........................................................................130 
9.5.5. 
Subgroup Analyses .............................................................................................130 
9.6. 
Interim Analyses ........................................................................................................131 
10. 
References ..................................................................................................................133 
11. 
Supporting Documentation and Operational Considerations ....................................137 
11.1. 
APPENDIX 1: Schedules of Events ..........................................................................138 
11.2. 
APPENDIX 2: Study Governance Considerations ....................................................160 
11.2.1. 
Regulatory and Ethical Considerations ..............................................................160 
11.2.2. 
Study Monitoring ...............................................................................................160 
11.2.3. 
Audits and Inspections .......................................................................................162 
11.2.4. 
Financial Disclosure ...........................................................................................162 
11.2.5. 
Recruitment Procedures .....................................................................................162 
11.2.6. 
Informed Consent Process ..................................................................................162 
11.2.7. 
Protocol Amendments ........................................................................................163 
11.2.8. 
Protocol Deviations ............................................................................................164 
11.2.9. 
Data Protection ...................................................................................................164 
11.2.10. 
Sample Retention and Future Biomedical Research ..........................................165 
11.2.11. 
Data Quality Assurance and Quality Control .....................................................166 
11.2.12. 
Data Collection and Management ......................................................................167 
11.2.13. 
Source Documents..............................................................................................167 
11.2.14. 
Retention of Records ..........................................................................................168 
11.2.15. 
Study and Site Closure .......................................................................................168 
11.2.16. 
Publication Policy ..............................................................................................169 

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11.3. 
APPENDIX 3: Contraceptive Guidance ....................................................................170 
11.4. 
APPENDIX 4: Statistical Appendices .......................................................................172 
11.4.1. 
Estimands and Estimand Specifications .............................................................172 
11.4.2. 
Statistical Methods and Sensitivity Analyses.....................................................175 
11.5. 
APPENDIX 5: Adverse Events of Special Interest Terms ........................................176 
11.6. 
APPENDIX 6: Protocol Amendment History ...........................................................178 

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LIST OF TABLES 
Table 1: 
Objectives and Endpoints ......................................................................................54 
Table 2: 
Summary of Treatment Groups .............................................................................72 
Table 3: 
Grading of COVID-19 Symptoms .........................................................................92 
Table 4: 
Maximum Planned Immunogenicity Blood Sampling Volumes per Participant 
by Visit ...................................................................................................................99 
Table 5: 
Solicited Adverse Reactions and Grades .............................................................106 
Table 6: 
Conditions and Sample Size to Demonstrate Vaccine Efficacy ..........................117 
Table 7: 
Power of Demonstrating Vaccine Efficacy Against Severe COVID-19 .............118 
Table 8: 
Populations for Analyses .....................................................................................119 
Table 9: 
Statistical Analysis Methods of Efficacy Endpoints ............................................120 
Table 10: 
Treatment Cohorts for the Long-term Efficacy Analyses ....................................124 
Table 11: 
Long-term Efficacy Endpoints .............................................................................125 
Table 12: 
Analysis Strategy for Safety Parameters in Part A ..............................................127 
Table 13: 
Immunogenicity Endpoints and Statistical Methods ...........................................128 
Table 14: 
Burden of Disease Score ......................................................................................130 
Table 15: 
Interim Boundaries Using O’Brien-Fleming Spending Function, Calculation 
Based on the PP Set for the Primary Efficacy Endpoint ......................................132 
Table 16: 
Schedule of Events (Vaccination Phase, Day 1 – Day 57) ..................................139 
Table 17: 
Schedule of Events (Surveillance Phase, Day 64 – Day 394) .............................142 
Table 18: 
Schedule of Events (Surveillance Phase, Day 401 – Day 759) ...........................145 
Table 19: 
Schedule of Events (Convalescent Period, Starting With the Illness Visit) ........147 
Table 20: 
Part B: Participant Decision Visit ........................................................................149 
Table 21: 
Supplemental Schedule of Events: Open-Label Observational Phase - Placebo 
Participants who Request to Receive mRNA-1273 .............................................150 
Table 22: 
Modified Supplemental Schedule of Events: Open-Label Observational Phase 
– mRNA-1273 Participants Who ONLY Received 1 Dose of mRNA-1273.......153 
Table 23: 
Part C Supplemental Schedule of Events: Booster Dose Phase ..........................156 
Table 24: 
Intercurrent Event Types......................................................................................172 
Table 25: 
Primary Objective and Estimands With Rationale for Strategies to Address 
Intercurrent Events for Per-protocol Analysis .....................................................173 
Table 26: 
Summary of Statistical Methods and Sensitivity Analyses .................................175 
Table 27: 
Adverse Events of Special Interest ......................................................................176 

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LIST OF FIGURES 
Figure 1: 
Study Flow Diagram: Part A, the Blinded Phase Followed by Part B, the 
Open-Label Phase Including Part C, the Booster Dose Phase ...............................35 
Figure 2: 
Part B, the Open-Label Observational Phase, and Part C, the Booster Dose 
Phase ......................................................................................................................36 
Figure 3: 
Surveillance for COVID-19 Symptoms and the Corresponding Clinical Data 
Pathways ................................................................................................................90 
Figure 4: 
Boundary Crossing Probabilities by Effect Size ..................................................117 
 

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LIST OF ABBREVIATIONS 
The following abbreviations and terms are used in this study protocol. 
Abbreviation 
Definition 
Ab 
antibody 
AC 
adjudication committee 
AE 
adverse event 
AESI 
adverse event of special interest 
AR 
adverse reaction 
bAb 
binding antibody 
BD 
booster dose 
BLA 
Biologics License Application 
BOD 
burden of disease 
BP 
blood pressure 
CDC 
US Centers for Disease Control and Prevention 
CEAC 
Cardiac Event Adjudication Committee 
CFR 
Code of Federal Regulations 
CI 
confidence interval 
CLIA 
Clinical Laboratory Improvement Amendments 
cMRI 
cardiac magnetic resonance imaging 
CONSORT 
Consolidated Standards of Reporting Trials 
CoV 
coronavirus 
COVID-19 
coronavirus disease 2019 
COV-INF 
virologically confirmed SARS-CoV-2 infection or COVID-19 regardless 
of symptomatology or severity 
CP 
convalescent plasma 
CRO 
contract research organization 
CSR 
clinical study report 
DHHS 
Department of Health and Human Services 
DMID 
Division of Microbiology and Infectious Diseases 
DSMB 
Data and Safety Monitoring Board 
DSPC 
1,2-distearoyl-sn-glycero-3-phosphocholine 
ECG/EKG 
electrocardiogram 
eCRF 
electronic case report form 
eDiary 
electronic diary 
EUA 
Emergency Use Authorization 
FAS 
full analysis set 

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Abbreviation 
Definition 
FDA 
Food and Drug Administration 
FSH 
follicle-stimulating hormone 
GCP 
Good Clinical Practice 
GMFR 
geometric mean fold rise 
GMT 
geometric mean titer 
HCP 
healthcare practitioner 
HIV 
human immunodeficiency virus 
HR 
hazard ratio 
HRT 
hormonal replacement therapy 
IA 
interim analysis 
IB 
investigator’s brochure 
ICF 
informed consent form 
ICH 
International Council for Harmonisation 
IM 
intramuscular 
IP 
investigational product 
IRB 
institutional review board 
IRT 
interactive response technology 
LLOQ 
lower limit of quantification 
LNP 
lipid nanoparticle 
LOD 
limit of detection 
LTFU 
lost to follow-up 
MAAE 
medically attended adverse event 
mAb 
monoclonal antibody 
MedDRA 
Medical Dictionary for Regulatory Activities 
MERS-CoV 
Middle East respiratory syndrome coronavirus 
mITT 
modified intent-to-treat 
mRNA 
messenger RNA 
nAb 
neutralizing antibody 
NIAID 
National Institute of Allergy and Infectious Diseases 
NP 
nasopharyngeal 
PCR 
polymerase chain reaction 
PDV 
participant decision visit 
PEG2000-DMG 
1-monomethoxypolyethyleneglycol-2,3-dimyristylglycerol with 
polyethylene glycol of average molecular weight 2000 
PP 
per-protocol 

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Abbreviation 
Definition 
PSRT 
Protocol Safety Review Team 
RT-PCR 
reverse transcriptase polymerase chain reaction 
S 
Spike 
S-2P 
spike protein with 2 proline residues introduced for stability in a 
prefusion conformation 
SAE 
serious adverse event 
SAP 
statistical analysis plan 
SARS-CoV-2 
severe acute respiratory syndrome coronavirus 2 
 
 
 
SoE 
Schedule of Events 
SRR 
seroresponse rate 
TEAE 
treatment-emergent adverse event 
ULOQ 
upper limit of quantification 
USP 
United States Pharmacopeia 
VE 
vaccine efficacy 
WHO 
World Health Organization 
 
CCI

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2. 
INTRODUCTION 
2.1. 
Study Rationale 
Coronaviruses (CoVs) are a large family of viruses that cause illness ranging from the common 
cold to more severe diseases, such as Middle East respiratory syndrome CoV (MERS-CoV) and 
severe acute respiratory syndrome CoV (SARS-CoV). 
An outbreak of the CoV disease 2019 (COVID-19) caused by SARS-CoV-2 began in Wuhan, 
Hubei Province, China in December 2019 and has spread throughout China and to over 216 other 
countries and territories, including the United States (WHO 2020). On 11 Mar 2020, the World 
Health Organization (WHO) officially declared COVID-19 a pandemic. As of 28 May 2020, the 
WHO reported more than 5,593,631 confirmed cases and 353,334 deaths globally and the US 
Centers for Disease Control and Prevention (CDC) reported 1,698,523 confirmed and probable 
cases of COVID-19, with 100,446 deaths in the United States (CDC 2020a). The CDC have 
reported that the highest risk of disease burden is in older adults (≥ 65 years old) and people of any 
age who have serious underlying medical conditions, such as chronic lung disease or moderate to 
severe asthma; serious heart conditions; severe obesity; diabetes; chronic kidney disease requiring 
dialysis; liver disease; and those who are immunocompromised (CDC 2020b). 
At the time the present Phase 3 study was initiated, no vaccine against SARS-CoV-2 had been 
authorized or approved. Global efforts to evaluate novel antivirals and therapeutic strategies to 
treat severe SARS-CoV-2 infections have intensified, but no proven therapeutic currently exists. 
Therefore, there is an urgent public health need for rapid development of novel interventions to 
prevent the spread of this disease. The primary goal of this Phase 3 study is to evaluate the vaccine 
efficacy (VE) of mRNA-1273 to prevent COVID-19, compared to placebo.  
2.2. 
Background and Overview 
ModernaTX, Inc. (the Sponsor) has developed a rapid response, proprietary vaccine platform 
based on a messenger RNA (mRNA) delivery system. The platform is based on the principle and 
observations that cells in vivo can take up mRNA, translate it, and then express protein viral 
antigen(s) on the cell surface. The delivered mRNA does not enter the cellular nucleus or interact 
with the genome, is nonreplicating, and is expressed transiently. mRNA vaccines have been used 
to induce immune responses against infectious pathogens such as cytomegalovirus 
(NCT03382405), human metapneumovirus and parainfluenza virus type 3 (NCT03392389), Zika 
virus (NCT03325075), and influenza virus (NCT03076385 and NCT03345043). 
The Sponsor is using its mRNA-based platform to develop a novel lipid nanoparticle 
(LNP)-encapsulated mRNA-based vaccine against SARS-CoV-2 (mRNA-1273). mRNA-1273 
encodes for the full-length spike (S) protein of SARS-CoV-2, modified to introduce 2 proline 
residues to stabilize the S protein (S-2P) in a prefusion conformation. The CoV S protein mediates 

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attachment and entry of the virus into host cells (by fusion), making it a primary target for 
neutralizing antibodies (nAbs) that prevent infection (Johnson et al 2016; Wang et al 2015; 
Wang et al 2018; Chen et al 2017; Corti et al 2015; Yu et al 2015; Kim et al 2019; Widjaja et al 
2019). It has been confirmed that the stabilized SARS-CoV-2 S-2P antigen presents in the correct 
prefusion conformation (Wrapp et al 2020). 
The development of the mRNA-1273 vaccine is being accelerated to address the current 
SARS-CoV-2 outbreak as a result of the uniquely rapid and scalable manufacturing process for 
mRNA-1273. The primary goal of this Phase 3 study is to evaluate the VE of mRNA-1273 to 
prevent COVID-19, compared to placebo. 
2.2.1. 
Nonclinical Studies 
Nonclinical studies have demonstrated that CoV S proteins are immunogenic and S protein-based 
vaccines, including those based on mRNA delivery platforms, are protective in animals. Prior 
clinical studies of vaccines targeting related CoVs and other viruses have demonstrated that 
mRNA-based vaccines are safe and immunogenic. It is therefore anticipated that mRNA-1273 will 
generate robust immune responses to the SARS-CoV-2 S protein and will be well tolerated. In 
addition, mRNA-1273 has shown preliminary evidence of protection against SARS-CoV-2 in a 
murine model of infection (data on file). 
In support of development of mRNA-1273 for prophylaxis against SARS-CoV-2 infection, 
nonclinical immunogenicity, biodistribution, and safety studies have been completed with similar 
mRNA-based vaccines formulated in LNPs containing 
 
 
, the novel proprietary lipid used 
in the mRNA-1273 LNP formulation. 
A detailed review of nonclinical experience with mRNA-1273 vaccine is provided in the 
investigator’s brochure (IB). 
2.2.2. 
Clinical Studies 
The mRNA-1273 vaccine is currently being evaluated for safety and immunogenicity in a 
dose-ranging Phase 1 study (NCT04283461) sponsored and conducted by the Division of 
Microbiology and Infectious Diseases (DMID) of the National Institute of Allergy and Infectious 
Diseases (NIAID). The Phase 1 DMID study is an open-label dose-ranging study of mRNA-1273 
in healthy adult male and non-pregnant female participants in 3 age groups: age 18 to 55 years, 
inclusive (45 participants); age 56 to 70 years, inclusive (30 participants); and ≥ 71 years 
(30 participants). Each participant received an intramuscular (IM) injection (0.5 mL) of 
mRNA-1273 on Days 1 and 29 in the deltoid muscle and will be followed for 13 months after the 
second injection. Sera obtained from 41 participants who were convalescing from COVID-19 were 
included as a comparative control. 
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A total of 120 participants were enrolled, and 116 participants received the second injection. Three 
mRNA-1273 dose levels (25, 50, and 100 µg) administered 28 days apart have been assessed in 
participants 18 to 55 years, 56 to 70 years, and ≥ 71 years of age. The mRNA-1273 250-µg dose 
was not evaluated in participants 56 to 70 years and ≥ 71 years of age due to reactogenicity 
observed in 4 participants in the 250 µg (18 to 55 years) dose cohort. Across all age groups, 
solicited adverse reactions (ARs) were predominantly mild or moderate in severity and most 
commonly included fatigue, chills, headache, myalgia, and pain at the injection site. The incidence 
and severity of solicited ARs were generally dose dependent and increases in incidence and 
severity were generally observed after the second injection. The incidence of systemic reactions 
increased after the second injection, particularly at the highest (250 µg) dose. Four (27%) 
participants in the 250 μg dose cohort reported at least 1 severe solicited AR after the second 
injection, including feverishness, fatigue, fever, headache, myalgia, nausea, and erythema/redness. 
No serious adverse events (SAEs) were reported through Day 119, and no pause rules were 
triggered during the study. mRNA-1273 induced robust binding antibody (bAb) responses after 
2 injections. Notably, 100 µg of mRNA-1273 resulted in numerically higher S-2P-specific binding 
titers than 25 µg and 50 µg of mRNA-1273 in all age groups. Two injections of mRNA-1273 also 
induced robust nAb responses. The nAb response was marginal after the first injection but 
increased substantially after the second injection. The nAb response assessed by a pseudovirus 
neutralization assay at the 100 µg mRNA-1273 dose level was similar to that at the 250 µg 
mRNA-1273 dose level in the 18 to 55 years of age group and numerically higher than that 
observed at the 25 µg and 50 µg mRNA-1273 dose levels in the older age groups. The nAb 
response at the 100 µg dose level was similar across all age groups. 
mRNA-1273-P201 (Study 201; NCT04405076) is an ongoing Phase 2a, safety, reactogenicity, and 
immunogenicity study in healthy adults that provided confirmation of the immunogenicity of both 
the 100 μg and 50 µg doses. The study was designed as a randomized, observer-blind, 
placebo-controlled dose confirmation study (Part A). Two mRNA-1273 dose levels, 50 μg and 
100 μg, and placebo were evaluated in 2 age cohorts: Cohort 1 enrolled participants ≥ 18 to 
< 55 years old (300 participants), and Cohort 2 enrolled participants ≥ 55 years old 
(300 participants). A total of 600 participants received either mRNA-1273 or placebo according 
to a 1:1:1 randomization ratio; ie, within each age cohort, 100 participants each received 
mRNA-1273 50 μg, mRNA-1273 100 μg, or placebo. mRNA-1273 demonstrated an acceptable 
safety profile in the participant population enrolled in this study at both dose levels and both age 
cohorts, as observed through 6 months after the second injection.  
An amendment to the Study 201 protocol adapted the study design to include open-label 
interventional phases (Part B and Part C). Part B allowed unblinding of participants and offered 
2 injections of mRNA-1273 in an open-label manner, 28 days apart, to all participants who 
received placebo in Part A. Part B also offered a single booster dose (BD) of mRNA-1273 (50 μg) 

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to participants who received 1 or 2 doses of mRNA-1273 (50 μg or 100 μg) in Part A at least 
6 months prior. Part C was prompted by the need to proactively prepare for vaccination strategies 
that induce broader protection, including against emerging variants of SARS-CoV-2 such as 
B.1.351. Part C enrolled participants from Study 301 who received 2 doses of mRNA-1273 100 μg 
at least 6 months prior. Part C participants received a single injection of mRNA-1273.351 (20 μg 
or 50 μg) or mRNA-1273.351 mixture (50 μg total – 25 μg of mRNA-1273 and 25 μg of 
mRNA-1273.351).  
Vaccination with mRNA-1273 in Study 201 resulted in robust immune responses to SARS-CoV-2 
in participants 18 years and older at both dose levels, and persistence of immune response was 
observed up to 6 months after the second injection in Part A of the study. In Part A of Study 201, 
the time course and magnitude of antibody (Ab; both bAb and nAb) responses to mRNA-1273 
was similar between 100 µg and 50 µg dose levels at each postbaseline timepoint (Days 29, 43, 
57, and 209), although the 100 µg dose group had numerically greater responses. In Part B of 
Study 201, administration of a 50 µg BD of mRNA-1273 6 months or more after the primary series 
improved the immune responses to 1.7-fold the peak achieved after the primary vaccination series 
in the current mRNA-1273-P301 study, where efficacy of mRNA-1273 against COVID-19 was 
demonstrated.  
This present ongoing Phase 3 study (mRNA-1273-P301) is a pivotal Phase 3, efficacy, safety, and 
immunogenicity study that has provided the primary clinical evidence of VE and safety (see 
Section 4 for details of the study design). The study was designed as a randomized, observer and 
participant blind, placebo-controlled study of the efficacy, safety, and immunogenicity of 
mRNA-1273 compared to placebo. More than 30,000 participants 18 years of age and older were 
randomized 1:1 to mRNA-1273 100 μg or placebo based on 3 strata: ≥ 65 years of age, 18 to 
< 65 years of age and at increased risk for complications of COVID-19, and 18 to < 65 years of 
age and not at risk. The initial mRNA-1273 100 µg dose was followed by a second 100 µg dose 
28 days later. Participants are being followed for efficacy and safety until 24 months after the 
second dose. Vaccine efficacy was demonstrated based on the prespecified efficacy success 
criterion at the interim analysis (IA) (11 Nov 2020 dataset), based on a total of 95 adjudicated 
COVID-19 cases. The subsequent primary analysis of efficacy was performed with a total of 
196 adjudicated COVID-19 cases (25 Nov 2020 dataset) and was consistent with the IA. 
mRNA-1273 was subsequently granted emergency use authorization (EUA) in the US and 
conditional approvals worldwide.  
After EUA in the US was granted for mRNA-1273 and another mRNA COVID-19 vaccine, Part B, 
the Open-Label Observational Phase of the study was initiated. All participants in Part A were 
invited to proceed to Part B, starting with a participant decision visit (PDV) at the study site, at 
which participants were given the option to be unblinded to their original group assignment or 

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remain blinded. Unblinded participants who had received placebo in Part A had the choice to be 
vaccinated with mRNA-1273 in Part B.  
On 25 Aug 2021, Moderna announced that it had completed the rolling submission process for its 
Biologics License Application (BLA) to the US Food and Drug Administration (FDA) for the full 
licensure of the Moderna COVID-19 vaccine (mRNA-1273) for active immunization to prevent 
COVID-19 in individuals 18 years of age and older. mRNA-1273 showed durable efficacy of 93% 
through 6 months after the second dose. mRNA-1273 was highly immunogenic as measured by 
both bAb and nAb in both SARS-CoV-2 baseline-negative and baseline-positive individuals, as 
indicated by increased bAb and nAb levels 1 month after first injection (Day 29) and 1 month after 
second injection (Day 57). mRNA-1273 demonstrated an acceptable safety profile in the 
participant population enrolled in this study, having a reactogenicity profile consistent with 
parenteral vaccination and was generally well tolerated. No unexpected findings were identified 
in the final assessment of the randomized, blinded phase of the study (Part A). 
Protocol mRNA-1273-P301 Amendment 9 initiated Part C of the study (Section 4.1.3), providing 
for administration of a BD of mRNA-1273.  
2.3. 
Benefit/Risk Assessment 
2.3.1. 
Potential Benefits of Study Participation 
The target study population for this study is adults with no known history of SARS-CoV-2 
infection but whose locations or circumstances put them at high risk of COVID-19. The following 
benefits may accrue to participants: 
• The mRNA-1273 vaccine may be an effective vaccine against COVID-19. 
• A baseline (Day 1) evaluation for SARS-CoV-2 infection and ongoing surveillance for 
COVID-19 throughout the study. 
• Contributing to the development of a vaccine against COVID-19, a current pandemic 
disease. 
2.3.2. 
Risks From Study Participation 
Immediate systemic allergic reactions (eg, anaphylaxis) can occur following any vaccination. 
These reactions are very rare and are estimated to occur once per 450,000 vaccinations for vaccines 
that do not contain allergens such as gelatin or egg protein (Zent et al 2002). As a precaution, all 
participants will remain under observation at the study site for at least 30 minutes after vaccination. 
Vasovagal syncope (fainting) can occur before or after any vaccination, is usually triggered by the 
pain or anxiety caused by the injection, and is not related to the substance injected. Therefore, it is 
important that standard precautions and procedures be followed to avoid injury from fainting. 

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Intramuscular injection with other mRNA vaccines manufactured by the Sponsor containing the 
 lipid formulation commonly results in a transient and self-limiting local inflammatory 
reaction. This typically includes pain, erythema (redness), or swelling (hardness) at the injection 
site, which are mostly mild to moderate in severity and usually occur within 24 hours of 
vaccination. More severe but self-limited local reactions, erythema and induration, have been 
observed at doses of mRNA-1273 exceeding the dose proposed in this study. 
Most systemic ARs observed after vaccination do not exceed Grade 1 to Grade 2 in severity. The 
most commonly reported systemic ARs are anticipated to be fever, fatigue, chills, headache, 
myalgias, and arthralgias. More severe reactions, including erythema, induration, fever, headache, 
and nausea were reported after receiving doses of mRNA-1273 that were greater than the dose 
proposed for use in this study. In all cases, the reactions resolved spontaneously. 
Laboratory abnormalities (including increases in liver functional tests and serum lipase levels) 
following vaccination were observed in clinical studies with similar mRNA-based vaccines. These 
abnormalities were without clinical symptoms or signs and returned toward baseline (Day 1) 
values over time. The clinical significance of these observations is unknown. Further details are 
provided in the current IB. 
There is a theoretical risk that active vaccination to prevent the novel viral infection caused by 
SARS-CoV-2 may cause a paradoxical increase in the risk of disease. This possibility is based on 
the rare phenomenon of vaccine-associated disease enhancement which was first seen in the 1960s 
with 2 vaccines made in the same way (formalin-inactivated whole virus) and designed to protect 
children against infection with respiratory syncytial virus (Chin et al 1969) or measles (Fulginiti et 
al 1967). Disease enhancement has also been proposed as a possible explanation for cases of more 
serious disease associated with dengue vaccination (Thomas and Yoon 2019; WHO 2019).  
To monitor the risk of enhanced disease in this study, an independent Data and Safety Monitoring 
Board (DSMB) will review unblinded cases of COVID-19 to assess for inefficacy and also for 
numerical imbalance in cases of both COVID-19 and severe COVID-19 with the purpose of 
providing a non-binding recommendation to the Sponsor (Section 8.4.2). To date, clinical 
immunogenicity data from the DMID Phase 1 study of mRNA-1273 demonstrated high levels of 
nAbs and Th-1-polarized CD4+ T-cell responses (Jackson et al 2020). In addition, in Study P301, 
after a median follow-up of 2 months after the second dose of vaccine, the overwhelming majority 
of COVID-19 cases occurred in participants who received placebo rather than mRNA-1273 
(Baden et al 2020), consistent with a low risk of enhanced respiratory disease following 
vaccination with mRNA-1273. These data suggest that a paradoxical increase in the risk of disease, 
while not eliminated, is likely to be low. Further details are provided in the current IB. 
In the context of the EUA for individuals 18 years and older for mRNA-1273, there have been 
very rare reports of myocarditis and pericarditis occurring after vaccination with Moderna 
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COVID-19 vaccine. Further details about this risk are described in the Fact Sheets (available on 
www.fda.gov). Although causality has not been established, the majority of the cases have been 
reported in young males shortly after the second dose of the vaccine. These are typically mild cases 
and individuals tend to recover within a short time following standard treatment and rest 
(Gargano et al 2021). 
The adverse events (AEs) after getting a third dose of mRNA-1273 are currently being studied. It 
is unknown if the AEs after getting a third dose of mRNA-1273 are different from getting 2 doses 
of mRNA-1273. Based on cumulative evidence, the benefit-risk profile of a BD of mRNA-1273 
is favorable, particularly in light of increasing breakthrough disease with the emergence of 
variants. 
2.3.3. 
Overall Benefit/Risk Conclusion 
All participants will be included based on their increased risk of SARS-CoV-2 infection. 
Accordingly, all will benefit from baseline and ongoing evaluations for SARS-CoV-2 infection. 
Since this is a placebo-controlled study (Section 4), half the participants will have the potential to 
receive mRNA-1273 vaccine, the efficacy of which is unknown at present. Vaccination with 
mRNA-1273 may not prevent COVID-19 in all vaccinees. 
Participants who receive placebo as part of this study may have an opportunity cost of not being 
treated with another investigational vaccine against COVID-19. 
The placebo for this study is a saline solution, without any LNP. Thus, participants receiving saline 
may be at lower risk of AEs related to injection than participants receiving mRNA-1273. 
Safety findings will be monitored and periodically reviewed by the DSMB to evaluate the safety 
and treatment status of all participants. The DSMB will review and assess the safety data as 
described in Section 8.4.2. 
Considering the lack of approved vaccines for COVID-19 prior to initiation of the study, the 
participants’ risk of COVID-19 outside the study, and the nonclinical and clinical data to date, the 
Sponsor considers the potential benefits of participation to exceed the risks. 
Based on the interim results from the pivotal Phase 3 study, mRNA-1273 prevents COVID-19 and 
severe COVID-19. The demonstrated clinical benefit of mRNA-1273 is supported by evidence of 
a robust immune response both in terms of bAbs and nAbs as well as the induction of CD4+ T-cells 
with a Th-1 dominant phenotype. Based on administration of mRNA-1273 to approximately 
15,693 adults across all 3 clinical studies to date, there have been no emergent safety concerns and 
the AE profile is manifested largely by mild to moderate reactogenicity lasting 2 to 3 days. 
Additionally, interim results of the ongoing Moderna Phase 2a study (mRNA-1273-P201) 
demonstrate a favorable benefit-risk profile of a BD of mRNA-1273. 

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3. 
OBJECTIVES AND ENDPOINTS 
Table 1: 
Objectives and Endpoints 
Objectives and Endpoints 
Primary Objective 
Primary Endpoints 
Efficacy Objective (Primary): 
To demonstrate the efficacy of mRNA-1273 to 
prevent COVID-19. 
Efficacy Endpoints (Primary): Vaccine 
efficacy of mRNA-1273 to prevent the first 
occurrence of COVID-19 starting 14 days after 
the second dose of IP, where COVID-19 is 
defined as symptomatic disease based on the 
following criteria: 
• 
The participant must have experienced at 
least TWO of the following systemic 
symptoms: fever (≥ 38ºC), chills, 
myalgia, headache, sore throat, new 
olfactory and taste disorder(s), OR 
• 
The participant must have experienced at 
least ONE of the following respiratory 
signs/symptoms: cough, shortness of 
breath or difficulty breathing, OR clinical 
or radiographical evidence of pneumonia; 
AND 
• 
The participant must have at least 1 NP 
swab or saliva sample (or respiratory 
sample, if hospitalized) positive for 
SARS-CoV-2 by RT-PCR 
Safety Objective (Primary): 
To evaluate the safety and reactogenicity of 
2 injections of the mRNA-1273 vaccine given 
28 days apart. 
Safety Endpoint (Primary): 
• 
Solicited local and systemic ARs 
through 7 days after each dose of IP 
(Part A). 
• 
Unsolicited AEs through 28 days after 
each dose of IP (Part A [all participants] 
and Part C [only those who receive the 
BD]). 
• 
MAAEs or AEs leading to withdrawal 
through the entire study period. 
• 
SAEs throughout the entire study 
period. 

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Objectives and Endpoints 
Efficacy Objectives (Secondary) 
Efficacy Endpoints (Secondary) 
To evaluate the efficacy of mRNA-1273 to 
prevent severe COVID-19 
Vaccine efficacy of mRNA-1273 to prevent 
severe COVID-19, defined as first occurrence of 
COVID-19 starting 14 days after the second dose 
of IP, (as per the primary endpoint) AND any of 
the following: 
• 
Clinical signs indicative of severe 
systemic illness, respiratory rate ≥ 30 per 
minute, heart rate ≥ 125 beats per minute, 
SpO2 ≤ 93% on room air at sea level or 
PaO2/FIO2 < 300 mmHg, OR 
• 
Respiratory failure or acute respiratory 
distress syndrome (defined as needing 
high-flow oxygen, non-invasive or 
mechanical ventilation, or extracorporeal 
membrane oxygenation), evidence of 
shock (systolic BP < 90 mmHg, diastolic 
BP < 60 mmHg or requiring 
vasopressors), OR 
• 
Significant acute renal, hepatic, or 
neurologic dysfunction, OR 
• 
Admission to an intensive care unit or 
death 
To evaluate the efficacy of mRNA-1273 to 
prevent serologically confirmed SARS-CoV-2 
infection or COVID-19 regardless of 
symptomatology or severity. 
Vaccine efficacy of mRNA-1273 to prevent the 
first occurrence of either COVID-19 or 
SARS-CoV-2 infection starting 14 days after the 
second IP dose. 
This endpoint is a combination of COVID-19, 
defined as for the primary endpoint, and 
asymptomatic SARS-CoV-2 infection, determined 
by seroconversion assessed by bAb levels against 
SARS-CoV-2 as measured by a ligand-binding 
assay specific to the SARS-CoV-2 nucleocapsid 
protein and with a negative NP swab sample for 
SARS-CoV-2 at Day 1 (Section 8.1.1). 

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Objectives and Endpoints 
Efficacy Objectives (Secondary) 
Efficacy Endpoints (Secondary) 
To evaluate VE against a secondary definition of 
COVID-19. 
Vaccine efficacy of mRNA-1273 to prevent the 
secondary case definition of COVID-19 starting 
14 days after the second IP dose. 
The secondary case definition of COVID-19 is 
defined as the following systemic symptoms: 
fever (temperature ≥ 38ºC), or chills, cough, 
shortness of breath or difficulty breathing, fatigue, 
muscle aches or body aches, headache, new loss 
of taste or smell, sore throat, nasal congestion or 
rhinorrhea, nausea or vomiting, or diarrhea, AND 
a positive NP swab or saliva sample (or 
respiratory sample, if hospitalized) for 
SARS-CoV-2 by RT-PCR 
To evaluate VE to prevent death caused by 
COVID-19. 
Vaccine efficacy of mRNA-1273 to prevent death 
due to a cause directly attributed to a complication 
of COVID-19, starting 14 days after the second IP 
dose. 
To evaluate the efficacy of mRNA-1273 to 
prevent COVID-19 after the first dose of IP. 
Vaccine efficacy of mRNA-1273 to prevent the 
first occurrence of COVID-19 starting 14 days 
after the first dose of IP.  
To evaluate the efficacy of mRNA-1273 to 
prevent COVID-19 in all study participants, 
regardless of evidence of prior SARS-CoV-2 
infection. 
Vaccine efficacy of mRNA-1273 to prevent the 
first occurrence of COVID-19 starting 14 days 
after the second dose of IP regardless of evidence 
of prior SARS-CoV-2 infection determined by 
serologic titer against SARS-CoV-2 nucleocapsid 
(FAS analysis population, see Section 9.4). 
To evaluate the efficacy of mRNA-1273 to 
prevent asymptomatic SARS-CoV-2 infection. 
Vaccine efficacy to prevent the first occurrence 
of SARS-CoV-2 infection in the absence of 
symptoms defining COVID-19 starting 14 days 
after the second IP dose. SARS-CoV-2 infection 
determined by seroconversion assessed by bAb 
levels against SARS-CoV-2 as measured by a 
ligand-binding assay specific to the SARS-CoV-
2 nucleocapsid protein and with a negative NP 
swab sample for SARS-CoV-2 at Day 1 
(Section 8.1.1).  

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Objectives and Endpoints 
Immunogenicity Objective (Secondary): 
Immunogenicity Endpoints (Secondary):  
To evaluate the immunogenicity of 2 doses of 
mRNA-1273 given 28 days apart. 
• 
GMT of SARS-CoV-2-specific nAb on 
Day 1, Day 29, Day 57, Day 209, 
Day 394, and Day 759. 
• 
GMFR of SARS-CoV-2-specific nAb 
relative to Day 1 on Day 29, Day 57, 
Day 209, Day 394, and Day 759. 
• 
Quantified levels or GMT of S protein-
specific bAb on Day 1, Day 29, Day 57, 
Day 209, Day 394, and Day 759. 
• 
GMFR of S protein-specific bAb relative 
to Day 1 on Day 29, Day 57, Day 209, 
Day 394, and Day 759. 
Immunogenicity Objective (Secondary) for 
Part C: 
Immunogenicity Endpoints (Secondary) for 
Part C: 
To infer effectiveness of the 50 μg of 
mRNA-1273 booster by establishing 
noninferiority of Ab response after the BD 
compared to the primary series of mRNA-1273 
using GMT values of serum Ab and seroresponse 
rate of post booster in Part C compared with 
primary series recipients of mRNA-1273. 
Key secondary endpoints:  
• 
GMT of post-booster (post-BD-Day 1; 
BD-Day 29) Ab as compared to 
post-primary series mRNA-1273 (post-
Dose 2; Day 57)  
• 
Seroresponse rate of post-
booster/BD-Day 1 from baseline 
(pre-Dose 1) as compared to post-Dose 2 
from baseline (pre-Dose 1) in primary 
series recipients of mRNA-1273. 
Seroresponse is defined as a titer change 
from baseline (pre-Dose 1 in primary 
series) below the LLOQ to ≥ 4 × LLOQ, 
or at least a 4-fold rise if baseline is 
≥ LLOQ. 
Exploratory Objectives for Part A 
To evaluate the effect of mRNA-1273 on the viral infection kinetics as measured by viral load at 
SARS-CoV-2 infection diagnosis by RT-PCR and number of days from the estimated date of 
SARS-CoV-2 infection until undetectable SARS-CoV-2 infection by RT-PCR. 
To assess VE to reduce the duration of symptoms of COVID-19. 
To evaluate VE against all-cause mortality. 
To assess VE against burden of disease due to COVID-19. 
To evaluate the genetic and/or phenotypic relationships of isolated SARS-CoV-2 strains to the vaccine 
sequence. 
To evaluate immune response markers after dosing with IP as correlates of risk of COVID-19 and as 
correlates of risk of SARS-CoV-2 infection. 

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Objectives and Endpoints 
To conduct additional analyses related to furthering the understanding of SARS-CoV-2 infection and 
COVID-19, including analyses related to the immunology of this or other vaccines, detection of viral 
infection, and clinical conduct. 
Exploratory Objectives for Part C 
To evaluate the safety of a BD of mRNA-1273. 
To evaluate the immunogenicity of a BD of mRNA-1273.  
Abbreviations: Ab = antibody; AE = adverse event; AR = adverse reaction; bAb = binding antibody; BD = booster 
dose; BP = blood pressure; COVID-19 = coronavirus disease 2019; FAS = full analysis set; GMFR = geometric 
mean fold rise; GMT = geometric mean titer; IP = investigational product; LLOQ = lower limit of quantification; 
MAAE = medically attended adverse event; nAb = neutralizing antibody; NP = nasopharyngeal; RT-
PCR = reverse transcriptase polymerase chain reaction; S = spike; SAE = serious adverse event; SARS-CoV-
2 = severe acute respiratory syndrome coronavirus 2; VE = vaccine efficacy. 

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4. 
STUDY DESIGN 
4.1. 
General Design 
This is a 3-part Phase 3 study, comprising Part A, Part B, and Part C. Participants in Part A, the 
Blinded Phase of this study, were blinded to their treatment assignment. Given that the primary 
efficacy endpoint for mRNA-1273 against COVID-19 was met per the protocol-defined IA, Part B, 
the Open-Label Observational Phase of this study, was designed to offer eligible participants who 
received placebo in Part A of this study an option to request open-label mRNA-1273, subject to 
availability of investigational vaccine (Figure 1). Part C, the Booster Dose Phase, providing for an 
mRNA-1273 BD, is designed to offer eligible participants the option to request a BD of 
mRNA-1273.  
Upon entry into Part A, all participants had 8 scheduled clinic visits, including Screening, Day 1, 
Day 29, Day 57, Day 209, Day 394, Day 759, as specified in the Schedules of Events (SoEs) 
(Table 16, Table 17, Table 18, Table 19). With the initiation of Part B, a PDV was scheduled for 
all participants currently enrolled in Part A at that time (Table 20) and participants eligible for 
Part B dosing may have had up to 2 additional scheduled clinic visits as specified in SoEs (Table 21 
and Table 22). Part C will begin with a BD-1 visit (see SoE; Table 23) scheduled for all 
participants currently enrolled in Part B, and participants deciding to receive a BD may have up to 
3 additional clinic visits scheduled (Section 4.1.3; Table 23). 
This study will be conducted in compliance with the protocol, Good Clinical Practice (GCP), and 
all applicable regulatory requirements. 
4.1.1. 
Part A, the Blinded Phase 
The Blinded Phase of this study is a randomized, stratified, observer-blind, placebo-controlled 
evaluation of the efficacy, safety, and immunogenicity of mRNA-1273 SARS-CoV-2 vaccine 
compared to placebo in adults 18 years of age and older who have no known history of 
SARS-CoV-2 infection but whose locations or circumstances put them at appreciable risk of 
acquiring COVID-19 and/or SARS-CoV-2 infection. Figure 1 shows the study flow and 
Appendix 1 (Table 16, Table 17, Table 18, and Table 19) presents the planned SoEs. 
Approximately 30,000 participants will be randomly assigned to receive doses of either 100 µg of 
mRNA-1273 vaccine or a placebo control in a 1:1 randomization ratio. Assignment will be 
stratified by age and health risk (Section 6.2.1.1). This is a case-driven study and thus final sample 
size of the study will depend on the actual attack rate of COVID-19. 
All participants will be assessed for efficacy and safety endpoints and provide a nasopharyngeal 
(NP) swab sample and blood sample before the first and second dose of investigational product 
(IP), in addition to a series of post-dose blood samples for immunogenicity through 24 months 

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after the second dose of IP. Efficacy assessments will include surveillance for COVID-19 with 
reverse transcriptase polymerase chain reaction (RT-PCR) confirmation of SARS-CoV-2 infection 
after the first and second dose of IP. As noted above, this is a case-driven study: if the prespecified 
criteria for early efficacy are met at the time of either IA or overall efficacy at the primary analysis, 
a final study report describing the efficacy and safety of mRNA-1273 will be prepared based on 
the data available at that time. In the event that success criteria are met either at the time of the IA 
or when the total number of cases toward the primary endpoint have accrued, participants will 
continue to be followed in a blinded fashion until Month 25 to enable assessment of long-term 
safety and durability of VE. If the study concludes early, all participants will be requested to 
provide a final blood sample at the time of study conclusion. 
Each participant will receive 2 doses of IP by 0.5 mL IM injection, the first on Day 1 and the 
second on Day 29. An NP swab sample will be collected prior to the first and second dose of IP 
for evaluation by RT-PCR. To preserve observer blinding, only delegated unblinded study 
personnel responsible for study vaccine preparation, administration and/or accountability will have 
knowledge of study treatment assignment (Section 6.2.8.1). 
Participants will be given an electronic diary (eDiary) to report solicited ARs for 7 days after each 
dose of IP and to prompt an unscheduled clinic visit for clinical evaluation and NP swab sample if 
a participant experiences any symptoms of COVID-19 (throughout study). Participants will use 
the eDiary to report solicited ARs for 7 days after each dose of IP and weekly eDiary prompts 
(every 7 days) to elicit an unscheduled Illness Visit if the participant is experiencing COVID-19 
symptoms. All participants will receive safety calls on Day 8, Day 15, Day 22, Day 36, and Day 43 
that will serve both to monitor for unsolicited AEs and to monitor for symptoms of COVID-19. 
Safety telephone calls and eDiary safety prompts will be performed in conjunction with 
surveillance for COVID-19 according to the SoEs (Table 16, Table 17, Table 18, and Table 19) 
and are intended to capture SAEs, medically attended AEs (MAAEs), AEs leading to withdrawal, 
concomitant medications associated with these events, receipt of non-study vaccinations, and 
pregnancy (Section 8.2.1). If an eDiary prompt results in identification of a relevant safety event, 
a follow-up safety call will be triggered. 
Surveillance for COVID-19 will be performed through weekly contacts with the participant via a 
combination of telephone calls and completion of an eDiary starting at Day 1 through the end of 
the study (Section 8.1.2). Participants with symptoms of COVID-19 lasting at least 48 hours 
(except for fever and/or respiratory symptoms) will return to the clinic or will be visited at home 
by medically qualified site staff within 72 hours to collect an NP swab sample for RT-PCR testing 
for SARS-CoV-2 and other respiratory pathogens, or alternatively, if a clinic or home visit is not 
possible, will submit a saliva sample for SARS-CoV-2 RT-PCR testing (Section 8.1.1). 

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All study participants who experience COVID-19 symptoms and subsequently present for an 
Illness Visit (in-clinic or at home) will be given an instruction card listing symptoms and severity 
grading system along with a thermometer, an oxygen saturation monitor, and saliva collection 
tubes. The list of symptoms is presented in Section 8.1.2 and the severity scoring system is 
presented in Section 8.1.3. Study participants will be contacted by the investigator (or 
appropriately delegated study staff) daily with telemedicine visits through Day 14 (from the Illness 
Visit or initial COVID-19 contact) or until symptoms have resolved, whichever is later, and which 
may include symptoms persisting longer than the 28-day Convalescent Period. If symptoms persist 
beyond Day 60, then telemedicine calls can be reduced to weekly; however, the participant should 
still report the daily symptoms at that contact. During the telemedicine visit (preferably done in 
the evening), the participant will be asked to verbally report the severity of each symptom and 
their highest body temperature and lowest oxygen saturation for that day, and the investigator will 
determine if medical attention is required due to worsening of COVID-19 symptoms (Table 19). 
Study participants will collect their own saliva sample on 3, 5, 7, 9, 14, and 21 days after the initial 
Illness Visit meeting criteria for COVID-19 (defined as the date of onset of symptoms and positive 
virologic test). Finally, a Convalescent Visit will be scheduled approximately 28 days after the 
initial Illness Visit. At this visit, a saliva sample will be collected and a blood sample will be drawn 
for immunologic assessment of SARS-CoV-2 infection. 
At each dosing visit, participants will be instructed (Day 1) or reminded (Day 29) on how to 
document and report solicited ARs in the eDiary provided. Solicited ARs will be assessed for 
7 days after each IP dose and unsolicited AEs will be assessed for 28 days after each IP dose; 
SAEs, MAAEs, AEs leading to withdrawal, will be assessed throughout the study. 
Participants may experience AEs that necessitate an unscheduled visit. There may also be 
situations in which the investigator asks a participant to report for an unscheduled visit following 
the report of an AE. Additional examinations may be conducted at these visits as necessary to 
ensure the safety and well-being of participants during the study. Electronic case report forms 
(eCRFs) should be completed for each unscheduled visit. 
4.1.2. 
Part B, the Open-Label Observational Phase 
The Part B, the Open-Label Observational Phase of the study is prompted by the authorization of 
a COVID-19 vaccine under EUA. Transitioning the study to Part B permits all ongoing study 
participants to be informed of the availability and eligibility criteria of any COVID-19 vaccine 
made available under an EUA and the option to offer all ongoing study participants who request 
unblinding an opportunity to schedule a PDV to learn their original treatment assignment (placebo 
vs. mRNA-1273 vaccine).  

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Part B, the Open-Label Observational Phase of the study, also provides the opportunity for eligible 
study participants who previously received placebo, to actively request to receive 2 doses of 
mRNA-1273 vaccine (as long as investigational vaccine is available). All study participants will 
receive a notification letter and will be asked to schedule a PDV. Principal Investigators should 
consider current local public health guidance for administration of COVID-19 vaccines under 
EUA when determining the scheduling priority of participants. With regard to eligibility in Part B, 
the CDC-EUA guidance specifications will supersede eligibility criteria in the protocol. 
All participants will proceed to Part B, the Open-Label Observational Phase of the study, starting 
with a PDV (Figure 2). 
At the PDV, all participants will: 
• Be encouraged to remain in the ongoing study, 
• Be given the option to be unblinded as to their original group assignment (placebo vs. 
mRNA-1273 vaccine), 
• Be counselled about the importance of continuing other public health measures to limit the 
spread of disease including social distancing, wearing a mask, and hand-washing, 
• Sign a revised informed consent form (ICF), 
• Provide an NP swab sample for RT-PCR for SARS-CoV-2 and a blood sample for serology 
prior to unblinding.  
Figure 2 shows the Part B Study Flow schematic.  
The following participants will continue with the original study SoEs presented in Table 16, 
Table 17, Table 18, and Table 19 (Figure 2): 
• Participants who request to not be unblinded, 
• Participants who request to be unblinded and received mRNA-1273, and 
• Participants who request to be unblinded and received placebo and choose to remain on 
placebo. 
Participants who are unblinded, received placebo, are eligible, and request to receive mRNA-1273 
(as long as investigational vaccine is available) (Figure 2), will have the following clinic visits as 
shown in the Supplemental SoE (Table 21): 
• Open-label Dose 1 (OL-D1): To occur at the PDV or at a scheduled subsequent visit. 
• Open-label Dose 2 (OL-D29): To occur 28 days after Dose 1 on OL-D1. 
• Open-label Clinic Visit (OL-D57): To occur 1 month after Dose 2 on OL-D29. 

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• And in addition, continue to comply with the Original Study SoEs (Table 16, Table 17, 
Table 18, and Table 19) as applicable. 
• Participants who are unblinded, and received ONLY 1 dose of mRNA-1273 may be 
eligible to receive 1 more dose of mRNA-1273 if: They had a dosing error in Part A of the 
study that resulted in 1 dose of mRNA-1273 and 1 dose of placebo being administered. 
• They did not have an AE that contraindicated the second dose of mRNA-1273 in Part A of 
the study.  
• They did not withdraw consent in Part A of the study.  
• They did not complete their second dose in Part A of the study for reasons other than the 
above. 
If participants are eligible, and request to receive mRNA-1273 (Figure 2) will proceed to have the 
following clinic visits as shown in the Modified Supplemental SoEs (Table 22): 
• Their second dose on OL-D1: To occur at the PDV or at a scheduled subsequent visit. 
• Open-label Clinic Visit (OL-D29): To occur 1 month after Dose 2 on OL-D1.  
• And in addition, continue to comply with the Original Study SoEs (Table 16, Table 17, 
Table 18, and Table 19) as applicable. 
All participants remain on their original SoE to complete 24 months of follow-up after Dose 2; 
study participants who enter the Supplemental/Modified Supplemental SoE as described above do 
so in addition to their original SoE. Accordingly, all study participants will complete the full study 
follow-up to 24 months after the second dose of their original inoculation (mRNA-1273 or 
placebo) or 25 months after the first dose if the second dose is missed. 
At the point when the mRNA-1273 vaccine is no longer available for study use, any participant 
who schedules a PDV after this timepoint will be unblinded (with no option to stay blinded) but 
will not be offered to receive mRNA-1273 study vaccine. These participants will have all the same 
procedures performed as outlined in Table 20 with the exception of being offered to receive 
mRNA-1273 vaccine. There will be no scientific metric or ethical advantage for participants to 
remain blinded when most of the study has already been unblinded. If the participant wants to 
receive EUA vaccine outside of the study after being unblinded, they will need to be withdrawn 
from the study. 
After the BLA database lock (on 04 May 2021), any remaining participants who had not been 
unblinded were unblinded by the Moderna study team and received their unblinding treatment 
assignment (placebo vs. mRNA vaccine) via certified letter from the study site. These participants 
were not required to return to the site for an NP swab sample or blood draw. 

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4.1.3. 
Part C, the Booster Dose Phase  
Part C, the Booster Dose Phase providing a BD for all eligible participants who chose to receive 
one, is prompted by interim results of an ongoing Moderna Phase 2a study (mRNA-1273-P201), 
as described in Section 4.2. 
Each study participant will receive a notification letter and will be asked to schedule a BD-1 visit 
at their study site (Table 23). Principal Investigators should consider current local public health 
guidance for administration of COVID-19 vaccines under EUA and marketing authorization (if 
any) when determining the scheduling priority of participants. At the BD-1 visit, each participant 
will: 
• Be encouraged to remain in the ongoing study, 
• Sign a revised ICF that includes both updated safety information relevant to the ongoing 
study and a BD, and the option to receive a BD,  
• Be given the option to receive a BD consisting of a 50 µg dose of mRNA-1273, 
• Be counselled about the importance of continuing other public health measures to limit the 
spread of disease including social distancing, wearing a mask, and hand-washing. 
After the BD-1 visit, participants who do not receive a BD will continue with the Part C 
Supplemental SoE for the BD-2 and BD-3 visits but will not have the BD-1a visit or the safety 
calls (Table 23). 
Participants who request a BD and are eligible and have no contraindications to further dosing (see 
Section 7.1) will have the following study site visits and complete scheduled activities (subject to 
investigational vaccine availability) according to the Part C Supplemental SoE (Table 23):  
• BD-1 visit: Participants will receive a single 50 µg dose of mRNA-1273. 
• BD-1a visit: Optional, and subject to blood sample kit availability, Day 4, 3 days after BD 
on Day 1. 
• BD-2 visit: Day 29, 28 days after the BD on Day 1. 
• BD-3 visit: Day 181, 180 days after the BD on Day 1. 
The investigator is responsible for conducting all assessments as specified in the Part C 
Supplemental SoE, according to the schedule. As this Supplemental SoE is intended to occur in 
addition to the original SoEs (Table 16, Table 17, Table 18, and Table 19) being followed by all 
participants in Part B, there is a possibility for study visits to overlap. If visits overlap according 
to respective visit windows, a single visit may be done with the combined study procedures 
completed once (refer to Table 4 footnotes for more detailed instructions and exceptions).  

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4.2. 
Scientific Rationale for Study Design 
The mRNA-1273 vaccine is being developed to prevent COVID-19, the disease resulting from 
SARS-CoV-2 infection. The present study has been designed to primarily evaluate the clinical 
efficacy and safety of mRNA-1273 to prevent COVID-19 for up to 2 years after the planned second 
dose of mRNA-1273. The immunogenicity endpoints and detection of SARS-CoV-2 infection are 
secondary objectives. 
The design and focus of the study as designed for Part A were dependent on the then current 
COVID-19 pandemic, requiring identification of participant candidates at high risk of 
SARS-CoV-2 infection. This Phase 3 study was designed to be a randomized, stratified, 
observer-blind, placebo-controlled study to evaluate the efficacy, safety, and immunogenicity of 
mRNA-1273 SARS-CoV-2 vaccine compared to placebo in adults 18 years of age and older who 
had no known history of SARS-CoV-2 infection but whose locations or circumstances put them at 
appreciable risk of acquiring COVID-19 and/or SARS-CoV-2 infection.  
Following authorization of a COVID-19 vaccine under EUA, the study design was amended to 
include a transition to Part B, the Open-Label Observational Phase (Section 2.2.2). The 
demonstration of efficacy against COVID-19 with satisfactory safety data, at a time when the 
COVID-19 pandemic remained critical, warranted allowing those study participants who actively 
requested it to know their original assignment (placebo or mRNA-1273 vaccine) on study. 
Transitioning the study to the Open-Label Observational Phase permitted all ongoing study 
participants (a) to be informed of the availability and eligibility criteria of any COVID-19 vaccine 
made available under an EUA and (b) to schedule a study visit to know their original group 
assignment (placebo vs. mRNA-1273 vaccine). Part B also provided the opportunity for eligible 
study participants who previously received placebo to receive 2 doses of mRNA-1273 vaccine 
under open-label conditions. Prompted by the anticipated recommendations from the FDA and 
CDC regarding boosters, this study design was further amended to include a transition to Part C, 
the Open-Label Observational BD Phase. The interim results of an ongoing Moderna Phase 2a 
study (mRNA-1273-P201; NCT04405076), in which participants who, 6 to 8 months prior, 
received 2 doses of 50 µg or 100 µg of mRNA-1273 were administered a 50 µg booster of 
mRNA-1273. Results demonstrated enhanced immune responses compared to pre-boost levels and 
met the noninferiority criteria stipulated in the FDA Guidance on EUA for Vaccines to Prevent 
COVID-19 (DHHS 2021). In addition, no new safety signals emerged upon administration of the 
BD in Study mRNA-1273-P201. Based on cumulative evidence, the benefit-risk profile of a BD 
of mRNA-1273 is favorable, particularly in light of increasing breakthrough disease with the 
emergence of variants. With the wider availability of boosters under EUA, providing the option of 
a BD to all eligible participants currently enrolled in Part B is expected to promote retention of 
participants in the ongoing study and thereby defend the scientific integrity of the study for the 

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planned 2-year duration of follow-up after the completion of the primary vaccination series 
regimen. 
4.3. 
Choice of Dose and Control Product 
The primary vaccination series originally selected for Part A of this study, 2 doses of 100 µg 
mRNA-1273 administered 28 days apart, was based on assessment of available safety and 
immunogenicity data from Phase 1 studies of mRNA-1647 (NCT03382405), the DMID study 
20-0003 entitled “Phase I, Open-Label, Dose-Ranging Study of the Safety and Immunogenicity of 
2019-nCoV Vaccine (mRNA-1273) in Healthy Adults” (NCT04283461) and Study 201 
(Section 2.2.2). The primary vaccination series (at the 100-µg dose level) used in this study is 
being used in these studies, with evidence of safety and immunogenicity. At the time Part A was 
initiated, there was no licensed SARS-CoV-2 vaccine currently available to serve as a reference 
control; accordingly, 0.9% sodium chloride (normal saline) injection (United States Pharmacopeia 
[USP]) was used as a placebo control during Part A.  
For Part C, the provision of the option of a single BD for eligible participants during the 
Open-Label Observational Phase, the BD selected is 50 µg, based primarily on data from 
Study mRNA-1273-P201. In Part A of Study mRNA-1273-P201, the time course and magnitude 
of Ab (both bAb and nAb) responses to mRNA-1273 was similar between 100 µg and 50 µg dose 
levels at each postbaseline timepoint (Days 29, 43, 57, and 209), although the 100-µg dose group 
had numerically greater responses. In Part B of Study mRNA-1273-P201, administration of a 
50 µg BD of mRNA-1273 6 months or more after the primary series improved the immune 
responses to 1.7-fold the peak achieved after the primary vaccination series in the current 
mRNA-1273-P301 study, where efficacy of mRNA-1273 against COVID-19 was demonstrated. 
4.4. 
End of Study Definition 
Participants are considered to have completed the study if they complete the final visit at Day 759 
(Month 25), 24 months following their receipt of the original second dose of IP (where original 
refers to the IP received following randomization); if a participant did not receive a second dose 
of IP, their follow-up will be 25 months after first dose of IP. For participants who enter Part C, if 
visit BD-3 falls after Day 759 (Month 25), then BD-3 will be the final visit. 
The study duration will be approximately 26 months for each participant. This includes a screening 
period of up to 1 month and a study period of 25 months that includes the first dose of IP on Day 1 
and the second dose on Day 29 (Part A). The participant's final scheduled visit will be on Day 759 
(Month 25), 24 months after the second dose of IP on Day 29 (Month 1) or 25 months after the 
first dose if the second dose is missed. For participants who enter Part C, if visit BD-3 falls after 
Day 759 (Month 25), then BD-3 will be the final visit. 

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The end of study will be the final participant’s final scheduled visit at Day 759 (Month 25) or 
BD-3, whichever is later. 

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5. 
STUDY POPULATION 
The study population, adults at risk of SARS-CoV-2 infection who have no known history of 
SARS-CoV-2 infection, is a subset of the planned target population. Additionally, potential study 
participants at increased risk of complications from COVID-19 will be included since it is 
hypothesized that these participants might derive the greatest benefit from a vaccine. Participants 
≥ 65 years of age will be eligible for enrollment with or without underlying medical conditions 
further increasing their risk of severe COVID-19. 
Given the disproportionate disease burden of COVID-19 in racial and ethnic minorities, the study 
will also aim to enroll a representative sample of participants from these minority population and 
adjust site selection and enrollment accordingly, per FDA Draft Guidance “Enhancing the 
Diversity of Clinical Trial Populations - Eligibility Criteria, Enrollment Practices, and Trial 
Designs” (DHHS 2020b). Study sites may be selected on the basis of SARS-COV-2 infection risk 
of the local population as well. Approximately 30,000 participants will be enrolled. 
There will be no prospective approval of protocol deviations to recruitment and enrollment criteria 
(also known as protocol waivers or exemptions). 
5.1. 
Inclusion and Exclusion Criteria (Part A, Part B, and Part C)  
5.1.1. 
Inclusion Criteria  
Participants are eligible to be included in the study, or further dosing (Part B and Part C), only if 
all the following criteria apply: 
1. (Part A only) Adults, ≥ 18 years of age at time of consent, who are at high risk of 
SARS-CoV-2 infection, defined as adults whose locations or circumstances put them at 
appreciable risk of exposure to SARS-CoV-2 and COVID-19  
2. Understands and agrees to comply with the study procedures and provides written 
informed consent. 
3. Able to comply with study procedures based on the assessment of the investigator. 
4. Female participants of nonchildbearing potential may be enrolled in the study. 
Nonchildbearing potential is defined as surgically sterile (history of bilateral tubal 
ligation, bilateral oophorectomy, hysterectomy) or postmenopausal (defined as 
amenorrhea for ≥ 12 consecutive months prior to Screening without an alternative 
medical cause). A follicle-stimulating hormone (FSH) level may be measured at the 
discretion of the investigator to confirm postmenopausal status (see additional 
information in Appendix 11.3). 

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5.  Female participants of childbearing potential may be enrolled in the study if the 
participant fulfills all the following criteria: 
• Has a negative pregnancy test at Screening and on the day of the first dose (Day 1, 
OL-D1, and BD-1). 
• Has practiced adequate contraception or has abstained from all activities that could 
result in pregnancy for at least 28 days prior to the first dose (Day 1, OL-D1, and 
BD-1). 
• Has agreed to continue adequate contraception through 3 months following the last 
dose (Day 29, OL-D29, and BD-1). 
• Is not currently breastfeeding. 
Adequate female contraception is defined as consistent and correct use of an FDA 
approved contraceptive method in accordance with the product label. For example: 
• Barrier method (such as condoms, diaphragm, or cervical cap) used in conjunction 
with spermicide 
• Intrauterine device 
• Prescription hormonal contraceptive taken or administered via oral (pill), transdermal 
(patch), subdermal, or IM route 
• Sterilization of a female participant’s monogamous male partner prior to entry into 
the study 
Note: periodic abstinence (eg, calendar, ovulation, symptothermal, post-ovulation 
methods) and withdrawal are not acceptable methods of contraception. 
6. Healthy adults or adults with pre-existing medical conditions who are in stable condition. 
A stable medical condition is defined as disease not requiring significant change in 
therapy or hospitalization for worsening disease during the 3 months before enrollment. 
7. (Part C Only) Is currently enrolled in Part B of the current study (mRNA-1273-P301). 
8. (Part C Only) Has received at least 1 dose of mRNA-1273 in the current study 
(mRNA-1273-P301). 
5.1.2. 
Exclusion Criteria 
Participants are excluded from the study or further dosing (Part B and Part C) if any of the 
following criteria apply: 

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1. Is acutely ill or febrile 72 hours prior to or at Screening or dosing (Part B and Part C). 
Fever is defined as a body temperature ≥ 38.0°C/100.4°F. Participants meeting this 
criterion may be rescheduled within the relevant window periods. Afebrile 
participants with minor illnesses can be enrolled/dosed at the discretion of the 
investigator. 
2. Is pregnant or breastfeeding. 
3. (Part A Only) Known history of SARS-CoV-2 infection. 
4. Prior (Part A) or concurrent (Part B and Part C) administration of a non-study 
coronavirus (SARS-CoV, MERS-CoV) vaccine or current/planned simultaneous 
participation in another interventional study to prevent or treat COVID-19  
5. (Part A Only) Demonstrated inability to comply with the study procedures. 
6. An immediate family member or household member of this study’s personnel. 
7. Known or suspected allergy or history of anaphylaxis, urticaria, or other significant 
AR to the vaccine or its excipients. 
8. Bleeding disorder considered a contraindication to IM injection or phlebotomy. 
9. Has received or plans to receive a non-study vaccine within 28 days prior to or after 
any dose of IP (except for seasonal influenza vaccine which is not permitted within 
14 days before or after any dose of IP, see Section 6.4.3). 
10. (Part A only) Has participated in an interventional clinical study within 28 days prior 
to the day of enrollment. 
11. Immunosuppressive or immunodeficient state, asplenia, recurrent severe infections 
(human immunodeficiency virus [HIV]-positive participants with CD4 count 
≥ 350 cells/mm3 and an undetectable HIV viral load within the past year [low level 
variations from 50-500 viral copies which do not lead to changes in antiretroviral 
therapy are permitted]). 
12. Has received systemic immunosuppressants or immune-modifying drugs for 
> 14 days in total within 6 months prior to IP dose administration (for corticosteroids 
≥ 20 mg/day of prednisone equivalent).  
13. Has received systemic immunoglobulins or blood products within 3 months prior to 
the day of IP dose administration. 
14. Has donated ≥ 450 mL of blood products within 28 days prior to IP dose 
administration. 

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5.2. 
Participant Restrictions 
Participants must not eat or drink anything hot or cold within 10 minutes before oral temperature 
is taken. 
5.3. 
Screen Failures (Part A, Blinded Phase Only) 
Screen failures are defined as participants who consent to participate in the clinical study but are 
not subsequently randomly assigned to treatment. A minimum set of screen failure information is 
required to ensure transparent reporting of screen failures to meet the Consolidated Standards of 
Reporting Trials (CONSORT) publishing requirements and to respond to queries from regulatory 
authorities. Minimum information includes date of informed consent, demography, screen failure 
details, eligibility criteria, and information on any SAE that may have occurred from the time 
informed consent was obtained to the time of withdrawal. 
Participants meeting the exclusion criterion #1, acutely ill or febrile prior to or at the Screening 
Visit (exclusion criterion #1, Section 5.1.2), may be rescheduled within the relevant window 
periods and will retain their initially assigned participant number. 

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6. 
STUDY TREATMENT 
6.1. 
Investigational Product 
The term “investigational product” refers to both mRNA-1273 vaccine (blinded and open-label) 
and placebo administered in this study. 
The mRNA-1273 IP is an LNP dispersion of an mRNA encoding the prefusion stabilized S protein 
of SARS-CoV-2 formulated in LNPs composed of 4 lipids (1 proprietary and 3 commercially 
available): the proprietary ionizable lipid SM-102; cholesterol; 1,2-distearoyl-sn-glycero-
3-phosphocholine (DSPC); and 1-monomethoxypolyethyleneglycol-2,3-dimyristylglycerol with 
polyethylene glycol of average molecular weight 2000 (PEG2000-DMG). The mRNA-1273 
vaccine is provided as a sterile liquid for injection and is a white to off-white dispersion in 
appearance, at a concentration of 0.2 mg/mL in 20 mM Tris buffer containing 87 mg/mL sucrose 
and 10.7 mM sodium acetate at pH 7.5. 
The placebo is 0.9% sodium chloride (normal saline) injection, which meets the criteria of the 
USP. 
6.2. 
Dosing and Management of Investigational Product 
6.2.1. 
Method of Randomly Assigning Participants to Treatment Groups (Part A, 
Blinded Phase Only) 
Approximately 30,000 participants will be randomly assigned in 1:1 ratio to receive either 
mRNA-1273 100 µg or placebo. The randomization will be in a blinded manner using a centralized 
interactive response technology (IRT), in accordance with pre-generated randomization schedules. 
Only the unblinded personnel (Section 6.2.8.1) will have controlled access to which arm the 
participant is randomly assigned. 
Dose group assignment in is summarized in Table 2. 
Table 2: 
Summary of Treatment Groups 
Treatment Groups 
Investigational Product 
Age (years) 
Estimated Total 
Participants 
mRNA-1273  
mRNA-1273 100 µg 
≥ 18 
15,000 
Placebo  
Placebo 
≥ 18 
15,000 
Total 
 
 
30,000 
6.2.1.1. 
Stratification 
Randomization in Part A, Blinded Phase of the study will be stratified based on age and, if they 
are < 65 years of age, based on the presence or absence of risk factors for severe illness from 
COVID-19 based on CDC recommendation as of March 2020 (CDC 2020b). There will be 3 strata 

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for randomization: ≥ 65 years, < 65 years and categorized to be at increased risk (“at risk”) for the 
complications of COVID-19, and < 65 years “not at risk.” Risk will be defined based on the study 
participants’ relevant past and current medical history. At least 25% of enrolled participants, up to 
50%, will be either ≥ 65 years of age or < 65 years of age and “at risk” at Screening. 
Participants who are < 65 years old will be categorized as at risk for severe COVID-19 illness if 
they have at least 1 of the following risk factors at Screening: 
• Chronic lung disease (eg, emphysema and chronic bronchitis), idiopathic pulmonary 
fibrosis and cystic fibrosis) or moderate to severe asthma 
• Significant cardiac disease (eg, heart failure, coronary artery disease, congenital heart 
disease, cardiomyopathies, and pulmonary hypertension) 
• Severe obesity (body mass index ≥ 40 kg/m2) 
• Diabetes (Type 1, Type 2, or gestational) 
• Liver disease 
• HIV infection 
6.2.2. 
Administration of Investigational Product 
In Part A and Part B, as applicable, IP will be administered as an IM injection into the deltoid 
muscle on a 2-dose injection schedule on Day 1 and Day 29. For injections administered for Part A 
and Part B, each injection will have a volume of 0.5 mL and contain mRNA-1273 100 µg or saline 
placebo. For Part C, each injection will have a volume of 0.25 mL and contain mRNA-1273 50 µg. 
Preferably, vaccine should be administered into the nondominant arm. The second dose of IP 
should be administered in the same arm as the first dose (Part A and Part B, as applicable). 
The IP will be prepared for injection as a single 0.5 mL (Part A and Part B) or 0.25 mL (Part C) 
dose for each participant per protocol, as detailed in the Pharmacy Manual. Unblinded personnel 
who will not participate in any other aspect of the study during Part A, the Blinded Phase, will 
perform IP accountability, dose preparation, and IP administration. The investigator will designate 
unblinded medically qualified personnel (not involved in assessments of study endpoints) to 
administer the IP according to the procedures stipulated in this study protocol (Part A, the Blinded 
Phase), and Pharmacy Manual. Study-specific training will be provided. Study site personnel who 
were blinded during the Blinded Phase will be unblinded at the participant level at the PDV. 
At each visit when IP is administered, participants will be monitored for a minimum of 30 minutes 
after administration. Assessments will include vital sign measurements and monitoring for local 
or systemic reactions (Table 16, Table 21, Table 22, and Table 23). 
Eligibility for a subsequent dose of IP is determined by following the criteria outlined in Section 7. 

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The study site will be appropriately staffed with individuals with basic cardiopulmonary 
resuscitation training/certification. Either on-site resuscitation equipment and personnel or 
appropriate protocols for the rapid transport of participant to a resuscitation area/facility are 
required. 
6.2.3. 
Delivery and Receipt 
The Sponsor or designee is responsible for the following: 
• Supplying the IP 
• Confirming the appropriate labeling of mRNA-1273 IP, so that it complies with the legal 
requirements of the US 
The investigator is responsible for acknowledging the receipt of the IP by a designated staff 
member at the site, including the following: 
• Confirming that the IP was received in good condition 
• Confirmation that the temperature during shipment from the Sponsor to the investigator’s 
designated storage location was appropriate 
• Confirming whether the Sponsor has authorized the IP for use 
• Ensuring the appropriate dose level of mRNA-1273 is properly prepared using aseptic 
technique 
Further description of the IP and instructions for the receipt, storage, preparation, administration, 
accountability, and destruction of the IP are described in the mRNA-1273-P201 Pharmacy Manual. 
6.2.4. 
Packaging and Labeling 
The Sponsor will provide the investigator and study site with adequate quantities of mRNA-1273. 
The sterile vaccine product is packaged in a 10R glass vial with a 5.0-mL or 6.3-mL fill volume 
(Part A and Part B) or a 10R glass vial with an 8.0 mL fill volume (Part C). mRNA-1273 vaccine 
will have all required labeling per regulations and will be supplied to the pharmacy in an unblinded 
manner. Each vial will be individually labeled for future participant identification purposes. 
mRNA-1273 will be packaged and labeled in accordance with the standard operating procedures 
of the Sponsor or of its designee, Code of Federal Regulations Title 21 (CFR), Good 
Manufacturing Practice guidelines, International Council for Harmonisation (ICH) GCP 
guidelines, guidelines for Quality System Regulations, and applicable regulations. 
The Sponsor or Sponsor’s designee will supply the 0.9% sodium chloride injection for use as both 
a placebo and a diluent to mRNA-1273. The 0.9% sodium chloride bears a commercial label and 
does not contain study-specific identification (Part A only). 

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6.2.5. 
Storage 
The vials of mRNA-1273 with 5.0 ml fill volume must be stored at 2°C to 8°C in a secure area 
with limited access (unblinded personnel only) and protected from moisture and light until it is 
prepared for administration (Section 6.2.2). The vials of mRNA-1273 with 6.3 mL or 8.0 mL fill 
volume must be stored at -20°C in a secure area with limited access and protected from moisture 
and light until it is prepared for administration. The vials of mRNA-1273 with 6.3 mL fill volume 
can be stored at 2°C to 8°C for up to 30 days, but site personnel must account for this manually as 
it will not be managed in the IRT system. The freezer or refrigerator should have automated 
temperature recording and a 24-hour alert system in place that allows for rapid response in case of 
freezer or refrigerator malfunction. There must be an available backup freezer or refrigerator. The 
freezers or refrigerators must be connected to a backup generator. In addition, vaccine 
accountability study staff (eg, the unblinded personnel) are required to keep a temperature log to 
establish a record of compliance with these storage conditions. The site is responsible for reporting 
any mRNA-1273 that was not temperature controlled during shipment or during storage to the 
unblinded site monitor. Such mRNA-1273 will be retained for inspection by the unblinded monitor 
and disposed of according to approved methods. 
The 0.9% sodium chloride injection (USP) should be stored at 20ºC to 25ºC (68ºF to 77ºF) in a 
restricted access area (applicable to Part A only). 
6.2.6. 
Investigational Product Accountability 
It is the investigator’s responsibility that the unblinded personnel maintain accurate records in an 
IP accountability log of receipt of all IP, inventory at the site, dispensing of mRNA-1273 and 
placebo, IP injections, and return to the Sponsor or alternative disposition of used/unused products. 
An unblinded site monitor will review the inventory and accountability log during site visits and 
at the completion of the study. Additional details are found in the mRNA-1273-P301 Pharmacy 
Manual. 
6.2.7. 
Handling and Disposal 
An unblinded site monitor will reconcile the IP during the conduct and at the end of the study for 
compliance. Once fully reconciled at the site at the end of the study, the IP can be destroyed at the 
investigational site or at a Sponsor-selected third party, as appropriate. 
Investigational product may be destroyed at the study site only if permitted by local regulations 
and authorized by the Sponsor. A Certificate of Destruction must be completed and sent to the 
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6.2.8. 
Unblinding 
6.2.8.1. 
Planned Unblinding 
See Section 4.1.2 regarding the PDV.  
Part A, the Blinded Phase of this study is observer-blind. The investigator, study staff, study 
participants, site monitors, and Sponsor personnel (or its designees) will be blinded to the IP 
administered, with the following exceptions: 
• Unblinded personnel (of limited number) will be assigned to vaccine accountability 
procedures and will prepare IP for all participants. These personnel will have no study 
functions other than study vaccine management, documentation, accountability, 
preparation, and administration. They will not be involved in participant evaluations and 
will not reveal the identity of IP to either the participant or the blinded study site personnel 
involved in the conduct of the study unless this information is necessary in the case of an 
emergency. 
• Unblinded medically qualified study site personnel will administer the IP. They will not be 
involved in assessments of any study endpoints. 
• The dosing assignment will be concealed by having the unblinded personnel prepare the 
IP in a secure location that is not accessible or visible to other study staff. An opaque sleeve 
over the syringe used for injection will maintain the blind at the time of injection, as the 
doses containing mRNA-1273 will look different than placebo. Only delegated unblinded 
site staff will conduct the injection procedure. Once the injection is completed, only the 
blinded study staff will perform further assessments and interact with the participants. 
Access to the randomization code will be strictly controlled at the pharmacy. 
• Unblinded site monitors, not involved in other aspects of monitoring, will be assigned as 
the IP accountability monitors. They will have responsibilities to ensure that sites are 
following all proper IP accountability, preparation, and administration procedures. 
• An unblinded statistical and programming team will perform the pre-planned IAs 
(Section 9.6). 
• An independent DSMB will review the interim data to safeguard the interests of clinical 
study participants and to help ensure the integrity of the study. The DSMB will review 
unblinded statistical outputs and IA results, provided by the independent unblinded 
statistician, and make recommendations to the Sponsor (Section 8.4.2). 

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• At the initiation of Part B, the Open-Label Observational Phase of this study 
(Section 4.1.3), study site personnel who were blinded during the Blinded Phase will be 
unblinded at the participant level at the PDV. 
• If prespecified criteria for early efficacy are met by an IA or if the primary efficacy analysis 
is completed based on accrual of prespecified COVID-19 cases, pre-identified Sponsor and 
contract research organization (CRO) team members responsible for the analysis and 
reporting will be unblinded to treatment assignments in order to prepare a final study report. 
In order to maintain an observer-blind design, investigators, site staff, participants, and 
Sponsor and CRO staff with oversight of study conduct will remain blinded to treatment 
allocation for the study duration. All study participants will be followed for efficacy and 
safety endpoints through the remainder of planned study period and results will be 
summarized in an end of study report (Sections 4.1 and 9.1). 
6.2.8.2. 
Unplanned Unblinding 
A participant or participants may be unblinded in the event of an SAE or other severe event, or if 
there is a medical emergency requiring the identity of the product to be known to properly treat a 
participant. If a participant becomes seriously ill or pregnant during the study, the study 
investigator may request that the blind will be broken if knowledge of the administered vaccine 
will affect that participant’s dosing options. In this situation or in the event of a medical emergency 
requiring identification of the IP administered to an individual participant, the investigator will 
make every attempt to contact the Sponsor medical lead to explain the need for opening the code 
within 24 hours of opening the code. The investigator will be responsible for documenting the 
time, date, reason for the code break, and the names of the personnel involved. 
In addition to the situations described above where the blind may be broken, the data will also be 
unblinded to a statistical team at specified timepoints for IAs as outlined in Section 9.6. 
In December 2020, COVID-19 vaccines started to become available under EUA as an alternative 
option to some participants based on evolving recommended populations by the CDC and local 
supply chain distribution. While all participants should be encouraged to stay blinded in the study 
for as long as possible, their participation should not otherwise deny them the opportunity to 
receive a COVID-19 vaccine under EUA. Clinical investigators can exercise discretion as to 
whether individual participants should be unblinded upon request to allow them to make an 
informed decision regarding receipt of a COVID-19 vaccine outside of this study. Investigator 
judgment should consider a participant’s risk status under CDC recommendations, any current 
local public health guidance, and their access to imminently receive a COVID-19 vaccine under 
an EUA. 

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If a decision is made to unblind a participant to support an informed decision to receive a 
COVID-19 vaccine under an EUA outside of this study, investigators are asked to take the 
following steps: 
• Obtain a final assessment of safety from the participant to collect and resolve any 
outstanding safety experience. Verbal interview is sufficient. 
• Unblind the participant in the IRT and inform the participant of their treatment 
assignment. 
• Inform the Sponsor Medical Lead within 24 hours to confirm rationale for unblinding. 
Participants who are confirmed to have received placebo upon unblinding and intend to receive a 
COVID-19 vaccine under an EUA outside of this study will be withdrawn from the study at the 
point of unblinding (Section 7.3.1).  
Note: Participants who requested unblinding because of a stated imminent access to a COVID-19 
vaccine under an EUA outside of this study, were withdrawn from study, and then were unable to 
in fact receive a COVID-19 vaccine, will be permitted to re-enter this study upon re-consent to 
receive the mRNA-1273 vaccine once they are eligible (as long as investigational vaccine is 
available). 
6.3. 
Study Treatment Compliance 
All doses of IP will be administered at the study site under direct observation of unblinded 
medically qualified study personnel and appropriately recorded (date and time) in the eCRF. 
Unblinded personnel will confirm that the participant has received the entire dose of vaccine. If a 
participant does not receive vaccine or does not receive all of the planned doses, the reason for the 
missed dose will be recorded. Data will be reconciled with site accountability records to assess 
compliance. 
Participants who miss the second dose of IP due to noncompliance with the visit schedule and not 
due to a safety pause will still be required to follow the original visit and testing schedule as 
described in the protocol. Except for participants who withdraw consent or who are withdrawn 
from the study due to receipt of non-study COVID-19 primary series or first booster vaccine 
(Section 7.3.1), a participant who withdraws or is withheld from receiving the second dose of study 
vaccine in Part A or Part B will remain in the study and complete all efficacy, safety, and 
immunogenicity assessments required through the participant’s scheduled end of study. 
The study site is responsible for ensuring that participants comply with the study windows allowed. 
If a participant misses a visit, every effort should be made to contact the participant and complete 
a visit within the defined visit window (SoE Tables, Section 11.1). If a participant does not 
complete a visit within the time window, that visit will be classified as a missed visit (with the 

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exception of Dose 2 visits in Part A and Part B, as applicable) and the participant will continue 
with subsequent scheduled study visits. All safety requirements of the missed visit will be captured 
and included in the subsequent visit (eg, clinical laboratory testing, eDiary review for 
reactogenicity, immunologic testing, as applicable). 
6.4. 
Prior and Concomitant Therapy 
6.4.1. 
Prior Medications and Therapies 
Information about prior medications (including any prescription or over-the-counter medications, 
vaccines, or blood products) taken by the participant within the 28 days before providing informed 
consent (or as designated in the inclusion/exclusion requirements) will be recorded in the 
participant’s eCRF. 
6.4.2. 
Concomitant Medications and Therapies 
Study site staff must question the participant regarding any medications taken and vaccinations 
received by the participant and record the following information in the eCRF: 
• All non-study vaccinations administered within the period starting 28 days before the first 
dose of IP. 
• Seasonal influenza vaccine administered for the current influenza season (typically 
October through April in the Northern Hemisphere). 
• All concomitant medications and non-study vaccinations taken through 28 days after 
each dose of IP. Antipyretics and analgesics taken prophylactically (ie, taken in the 
absence of any symptoms in anticipation of an injection reaction) will be recorded as 
such. 
• Any concomitant medications used to prevent or treat COVID-19. 
• Any concomitant medications relevant to or for the treatment of an SAE or an MAAE. 
• Part A: Participant will be asked in the eDiary if they have taken any antipyretic or 
analgesic to treat or prevent fever or pain within 7 days after each IP injection, including 
the day of dosing. Reported antipyretic or analgesic medications should be recorded in 
the source document by the site staff during the post-injection study visits or via other 
participant interactions (eg, phone calls). 

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6.4.3. 
Concomitant Medications and Vaccines That May Lead to the Elimination of a 
Participant From Per-protocol Analyses 
The use of the following concomitant medications and/or vaccines will not require withdrawal of 
the participant from the study but may determine a participant’s eligibility to receive a second dose 
or evaluability in the per-protocol (PP) analysis (Analysis Sets are described in Section 9.4): 
• Any investigational or nonregistered product (drug or vaccine) other than the study 
vaccine used during the study period. 
• A non-study vaccine administered during the period from 28 days before through 28 days 
after each dose of IP or any seasonal influenza vaccine that was administered within 
14 days before or after any dose of IP. 
• Immunoglobulins and/or any blood products administered during the study period (except 
for treatment of COVID-19). 
• Medications that suppress the immune system (except for treatment of COVID-19). 
In addition, any participant confirmed to have received or plans to receive a non-study 
COVID-19 vaccine, either licensed or under EUA, may also not be included in the PP analysis 
(and may also be withdrawn from the study per Section 7.3.1 if non-study COVID-19 vaccine is 
primary series or first booster). 
If a participant takes a prohibited drug therapy, the investigator and the CRO’s medical monitor 
will make a joint decision about continuing or withholding further dosing from the participant 
based on the time the medication was administered, the drug’s pharmacology and 
pharmacokinetics, and whether use of the medication will compromise the participant’s safety or 
the interpretation of data. It is the investigator’s responsibility to ensure that details regarding the 
concomitant medications are adequately recorded in the eCRF. 
All medication and interventions necessary for the appropriate care for the study participant, 
particularly to treat COVID-19, should be administered and appropriately documented along with 
the AE. 

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7. 
DELAYING OR DISCONTINUING STUDY TREATMENT AND 
PARTICIPANT WITHDRAWAL FROM THE STUDY 
7.1. 
Criteria for Delay of Study Treatment 
Body temperature must be measured at the Day 1, Day 29, OL-D1, OL-D29, and BD-1 visits prior 
to any study treatment administration.  
The following events constitute criteria for delay of study treatment, and if any of these events 
occur at the time scheduled for dosing, the participant may be injected at a later date within the 
time window specified in Table 16, Table 21, Table 22, and Table 23, or the participant may be 
discontinued from dosing at the discretion of the investigator (Section 7.2): 
• Acute moderate or severe infection with or without fever at the time of dosing. 
• Fever, defined as body temperature ≥ 38.0°C (100.4°F) at the time of dosing. 
• Part B only: Diagnosed COVID-19 by detection of SARS-CoV-2 by RT-PCR and 
accompanying symptoms. Participant must be asymptomatic at the time of dosing, 
although they may still be RT-PCR positive, with the exception of fatigue and loss of 
sense of smell or taste, if by the investigator’s judgement these are deemed to be mild 
chronic sequelae. 
• Part C only: Seasonal influenza vaccine that was administered within 14 days of the 
BD-1 visit. 
• Part C only: Diagnosed COVID-19 by detection of SARS-CoV-2 by RT-PCR and 
accompanying symptoms after completion of the primary vaccination series in Part A or 
Part B. For all study participants who were confirmed to have COVID-19 infection after 
Dose 1 and Dose 2 of mRNA-1273 but before the booster, the BD-1 visit should be 
delayed for 90 days from the receipt of monoclonal Ab (mAb) or convalescent plasma 
(CP) if given as a part of treatment per CDC recommendations. For participants who did 
not receive mAb or CP, BD can be administered after a minimum of 30 days from the 
onset of COVID-19 symptoms and complete resolution of the acute illness (except 
fatigue and loss of sense of smell or taste). A delay of 90 days may be considered, if 
feasible. If these criteria delay the BD-1 visit date beyond the allowable window per the 
study timeline, the subject may not receive the dose as a part of the study. 
Participants with a minor illness without fever, as assessed by the investigator, can be administered 
IP. Participants with a fever of 38.0°C (100.4°F) or higher will be contacted within the time 
window acceptable for participation and reevaluated for eligibility. If the investigator determines 
that the participant’s health on the day of administration temporarily precludes dosing with IP, the 
visit should be rescheduled within the allowed interval for that visit. 

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7.2. 
Discontinuation of Study Treatment 
Every reasonable attempt will be made to follow up with participants for safety throughout the 
entire study period, even if further dosing is discontinued or the participant misses one or more 
visits. Except for participants who withdraw consent or who are withdrawn from the study due to 
receipt of non-study COVID-19 primary series or first booster vaccine (Section 7.3.1), a 
participant who withdraws or is withheld from receiving the second dose of study vaccine in Part 
A or Part B will be considered to have discontinued treatment but will remain in the study and 
complete all scheduled visits and assessments (Section 11.1). Except for participants who 
withdraw consent or who are withdrawn from the study due to receipt of non-study COVID-19 
primary series or first booster vaccine (Section 7.3.1), a participant who does not receive the BD 
in Part C will NOT be considered to have discontinued treatment and will remain in the study and 
complete all scheduled visits and assessments. 
The investigator, in consultation with the Sponsor’s medical monitor, may withhold a participant 
from further dosing if the participant experiences any of the following: 
• Becomes pregnant (Section 8.3.6) 
• Develops, during the course of the study, symptoms or conditions listed in the exclusion 
criteria 
• Experiences an AE (other than reactogenicity) after dosing that is considered by the 
investigator to be related to IP (Section 8.3.10) and is of Grade 3 (severe) or greater 
intensity (Section 8.3.9) 
• Experiences an AE or SAE that, in the judgment of the investigator, requires study IP 
withdrawal due to its nature, severity, or required treatment, regardless of the causal 
relationship to vaccine 
• Experiences a clinically abnormal vital sign measurement or finding on physical 
examination, or general condition that, in the judgment of the investigator, requires IP 
withdrawal 
The reason(s) for discontinuation from further dosing will be recorded in the eCRF. 
Prior to receiving a second dose of study vaccine in Part A or Part B and prior to receiving a BD 
in Part C (as applicable), participants will be reassessed to ensure that they continue to meet 
eligibility requirements as outlined below. 
The following events in a participant constitute absolute contraindications to any further dosing of 
the IP to that participant. If any of these events occur during the study, the participant must not 
receive additional doses of vaccine but will be encouraged to continue study participation for safety 
through end-of-study period as defined in Section 4.4. 

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• Part A only: Diagnosed COVID-19 by detection of SARS-CoV-2 in a Day 1 NP swab 
sample or COVID-19 diagnosed prior to Day 29. If COVID-19 is suspected on or prior to 
Day 29, further administration of IP must be withheld until COVID-19 test results are 
available. 
• Anaphylaxis or systemic hypersensitivity reaction following the administration of 
vaccine. 
• Any SAE judged by investigator or Sponsor to be related to study vaccine. 
• Any clinically significant medical condition that, in the opinion of the investigator, poses 
an additional risk to the participant if he/she continues to participate in the study. 
7.3. 
Participant Withdrawal From the Study 
7.3.1. 
Participant Withdrawal 
Participants who withdraw from the study will not be replaced. A “withdrawal” from the study 
refers to a situation wherein a participant does not return for the final visit planned in the protocol. 
The statistical management of participant withdrawals is discussed in Section 9. 
Participants can withdraw consent and withdraw from the study at any time, for any reason, 
without prejudice to further treatment the participant may need to receive. The investigator will 
request that the study participant complete all study procedures pending at the time of withdrawal. 
A participant who withdraws consent or who is withdrawn from the study may request destruction 
of any samples taken and not tested, and the investigator must document this in the site study 
records. If the participant withdraws consent for disclosure of future information, the Sponsor may 
retain and continue to use any data collected before such a withdrawal of consent (see 
Section 11.2.10). 
The Sponsor will continue to retain and use all research results that have already been collected 
for the study evaluation, unless the participant has requested destruction of these samples. All 
biological samples that have already been collected may be retained and analyzed at a later date 
(or as permitted by local regulations). 
If participant desires to withdraw from the study because of an AE, the investigator will try to 
obtain agreement to follow up with the participant until the event is considered resolved or stable 
and will then complete the end of study eCRF. 
Information related to the withdrawal will be documented in the eCRF. The investigator will 
document whether the decision to withdraw a participant from the study was made by the 
participant or by the investigator, as well as which of the following possible reasons was 
responsible for withdrawal: 

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• AE (specify) 
• SAE (specify) 
• Death 
• Lost to follow-up (LTFU) 
• Physician decision (specify) 
• Pregnancy 
• Protocol deviation 
• Study terminated by Sponsor 
• Withdrawal of consent by participant (specify); this includes participants who, at the 
PDV, withdraw consent from continuing in the study. 
• Other (specify) 
Participants who are withdrawn from the study because of AEs (including SAEs) must be clearly 
distinguished from participants who are withdrawn for other reasons. Investigators will follow up 
with participants who are withdrawn from the study as result of an SAE or AE until resolution of 
the event. 
Participants who are confirmed to have received placebo upon unblinding and intend to receive a 
COVID-19 vaccine either licensed or under an EUA outside of this study will be withdrawn from 
the study. In addition, any participant confirmed to have received or plans to receive a non-study 
COVID-19 vaccine for their primary series or first booster only, either licensed or under EUA, 
will be withdrawn from the study. If a participant has an ongoing AE or pregnancy at the time of 
receipt of a non-study COVID-19 primary series or first booster vaccine, the participant will 
remain in the study to allow follow-up until the resolution of the event. Participants receiving a 
second or subsequent non-study COVID-19 boosters will remain in the study and follow all study 
procedures.  
7.4. 
Lost to Follow-up 
Participants will be considered LTFU if they repeatedly fail to return for scheduled visits without 
stating an intention to withdraw consent and they cannot be contacted by the study site. The 
following actions must be taken if a participant fails to return to the clinic for a required study 
visit: 
• The site must attempt to contact the participant and reschedule the missed visit as soon as 
possible, counsel the participant on the importance of maintaining the assigned visit 
schedule, and ascertain whether the participant wishes to and/or should continue in the 
study. 

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• Before a participant is deemed LTFU, the investigator or designee must make every 
effort to regain contact with the participant (where possible, 3 telephone calls and, if 
necessary, a certified letter to the participant’s last known mailing address or local 
equivalent methods). These contact attempts (eg, dates of telephone calls and registered 
letters) should be documented in the participant’s medical record. A participant should 
not be considered LTFU until these efforts have been made. 
• Should the participant continue to be unreachable, he/she will be considered to have 
withdrawn from the study. 

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8. 
STUDY ASSESSMENTS AND PROCEDURES 
Before performing any study procedures, all potential participants will sign an ICF (as detailed in 
Section 11.2.6). Participants will undergo study procedures at the timepoints specified in the SoEs 
(Section 11.1). 
A participant also can be seen for an unscheduled visit at any time during the study. An 
unscheduled visit may be prompted by reactogenicity issues, Illness Visit criteria for COVID-19, 
or new or ongoing AEs. The site also has the discretion to make reminder phone calls or send text 
messages to inform the participant about visits, review eDiary requirements, or follow-up on 
ongoing or outstanding issues. 
In accordance with “FDA Guidance on Conduct of Clinical Trials of Medical Products during the 
COVID-19 Pandemic” (DHHS 2020a), investigators may convert study site visits to telemedicine 
visits with the approval of the Sponsor. Such action should be taken to protect the safety and 
well-being of study participants and study site staff or to comply with state or municipal mandates. 
General considerations for study assessments and procedures include the following: 
• Protocol waivers or exemptions are not allowed. The study procedures and their timing 
must be followed as presented in Section 11.1. Adherence to the study design 
requirements is essential and required for study conduct. 
• Immediate safety concerns should be discussed with the Sponsor immediately upon 
occurrence or awareness to determine if the participant should continue study treatment 
or participation in the study. 
• All screening evaluations must be completed and reviewed to confirm that potential 
participants meet all eligibility criteria. The investigator will maintain a screening log to 
record details of all participants screened and to confirm eligibility or record reasons for 
screening failure, as applicable. 
• Procedures conducted as part of the participant’s routine clinical management (eg, blood 
count) and obtained before signing of the ICF may be utilized for screening or baseline 
purposes provided the procedures met the protocol-specified criteria and were performed 
within the time frame defined in the SoE. 

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8.1. 
Efficacy and Immunogenicity Assessments and Procedures 
8.1.1. 
Efficacy Assessments Related to COVID-19 and SARS-CoV-2 Infection 
Each study participant will have an NP swab sample collected for SARS-CoV-2 testing by 
RT-PCR on Day 1 and Day 29, prior to receiving a dose of the IP as specified in the SoE 
(Section 11.1). 
COVID-19: 
To be considered as a case of COVID-19 for the evaluation of the Primary Efficacy Endpoint, the 
following criteria must be met: 
o The participant must have experienced at least TWO of the following systemic 
symptoms: fever (≥ 38ºC), chills, myalgia, headache, sore throat, new olfactory 
and taste disorder(s), OR 
o The participant must have experienced at least ONE of the following respiratory 
signs/symptoms: cough, shortness of breath or difficulty breathing, OR clinical or 
radiographical evidence of pneumonia; AND 
o The participant must have at least 1 NP swab or saliva sample (or respiratory 
sample, if hospitalized) positive for SARS-CoV-2 by RT-PCR. 
Severe COVID-19: 
To be considered severe COVID-19, the following criteria must be met: 
• Confirmed case of COVID-19 as per the Primary Efficacy Endpoint case definition, plus 
any of the following: 
o Clinical signs indicative of severe systemic illness, respiratory rate ≥ 30 per 
minute, heart rate ≥ 125 beats per minute, SpO2 ≤ 93% on room air at sea level or 
PaO2/FIO2 < 300 mmHg, OR 
o Respiratory failure or acute respiratory distress syndrome (defined as needing 
high-flow oxygen, non-invasive or mechanical ventilation, or extracorporeal 
membrane oxygenation), evidence of shock (systolic blood pressure [BP] 
< 90 mmHg, diastolic BP < 60 mmHg or requiring vasopressors), OR 
o Significant acute renal, hepatic, or neurologic dysfunction, OR 
o Admission to an intensive care unit or death. 
The secondary case definition of COVID-19 is defined as having any of the following systemic 
symptoms: fever (temperature ≥ 38ºC), or chills, cough, shortness of breath or difficulty breathing, 
fatigue, muscle aches, or body aches, headache, new loss of taste or smell, sore throat, nasal 

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congestion or rhinorrhea, nausea, or vomiting or diarrhea, AND a positive NP swab or saliva 
sample (or respiratory sample, if hospitalized) for SARS-CoV-2 by RT-PCR. 
Death attributed to COVID-19 is defined as any participant who dies during the study with a cause 
directly attributed to a complication of COVID-19. 
SARS-CoV-2 Infection: 
• SARS-CoV-2 infection is defined by seroconversion due to infection measured by bAb 
against SARS-CoV-2 nucleocapsid. Seroconversion is defined as follows for participants 
who are seronegative at Baseline: 
o Binding antibody levels against SARS-CoV-2 nucleocapsid either below the limit 
of detection (LOD) or lower limit of quantification (LLOQ) at Study Day 1 that 
increase to above or equal to LOD or LLOQ starting at Study Day 57 or later. 
8.1.2. 
Surveillance for COVID-19 Symptoms 
Surveillance for COVID-19 symptoms will be conducted by a combination of safety phone calls 
and eDiary completion as presented in the SoEs in Section 11.1, in addition to study site visits 
(Figure 3). If there is no response to an eDiary prompt for 2 days, the site staff will contact the 
study participant by phone. 
According to the CDC as of 10 Jun 2020 (CDC 2020c), patients with COVID-19 have reported a 
wide range of symptoms ranging from mild symptoms to severe illness. Throughout the study, to 
surveil for COVID-19, the following prespecified symptoms that meet the criteria for suspicion of 
COVID-19 will be elicited weekly from the participant and the presence of any one of these 
symptoms lasting at least 48 hours (except for fever and/or respiratory symptoms) will result in 
the site arranging an Illness Visit to collect an NP swab sample within 72 hours: 
• Fever (temperature ≥ 38ºC) or chills (of any duration, including ≤ 48 hours) 
• Shortness of breath or difficulty breathing (of any duration, including ≤ 48 hours) 
• Cough (of any duration, including ≤ 48 hours) 
• Fatigue 
• Muscle or body aches 
• Headache 
• New loss of taste or smell 
• Sore throat 
• Congestion or runny nose 

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• Nausea or vomiting 
• Diarrhea 
It is important to note that some of the symptoms of COVID-19 overlap with solicited systemic 
ARs that are expected after vaccination with mRNA-1273 (eg, myalgia, headache, fever, and 
chills). During the first 7 days after vaccination, when these solicited ARs are common, 
investigators should use their clinical judgement to decide if an NP swab sample should be 
collected (Part A). The collection of an NP swab sample prior to the Day 1 and Day 29 vaccination 
can help ensure that cases of COVID-19 are not overlooked. Any study participant reporting 
respiratory symptoms during the 7-day period after vaccination should be evaluated for 
COVID-19. 

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Figure 3: 
Surveillance for COVID-19 Symptoms and the Corresponding Clinical Data 
Pathways 
 
During the course of the study, participants with symptoms of COVID-19 will be asked to return 
within 72 hours or as soon as possible to the study site or medically qualified staff from the study 
site will conduct a home visit as soon as possible to collect an NP swab sample (for RT-PCR), 
collect a blood sample for immunologic analysis of SARS-CoV-2 infection, and to evaluate for 
COVID-19. Both study site visits and home visits are referred to as Illness Visits. An additional 
NP swab sample will be collected and tested for the presence of other respiratory pathogens. 
In addition, the study site may collect an additional (non-study/local) respiratory sample for 
SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as 
determined by local standards of care. If neither a study site visit or home visit is possible, 

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participants will be sent a saliva kit via courier or other Sponsor-approved method. The study site 
will arrange to retrieve a saliva sample by local courier or other Sponsor-approved method, and 
the sample will be tested by RT-PCR for SARS-CoV-2. If participants are confirmed to have 
SARS-CoV-2 infection, the investigator will notify the participant, and the participant’s primary 
care physician, of the diagnosis. If the study participant does not have a primary care physician, 
the investigator will assist them to obtain one. The participant will also be instructed on infection 
prevention measures consistent with local public health guidance. 
If scheduled, a study site Illness Visit includes assessments such as medical history, physical 
examination, blood sampling for clinical laboratory testing, and 2 NP swabs, 1 for viral polymerase 
chain reaction (PCR) SARS-CoV-2 testing and 1 for multiplex PCR testing for respiratory viruses, 
to evaluate the severity of the clinical case. Radiologic imaging studies may be conducted. Blood 
samples will be collected for potential future immunologic assessment of SARS-CoV-2 infection. 
Every effort to complete an Illness Visit that includes both the NP swabs and blood draw should 
be made by the site, even in the presence of a local positive or negative Clinical Laboratory 
Improvement Amendments (CLIA) certified or CLIA-certified waiver laboratory result for the 
participant. 
Cases are defined as participants meeting clinical criteria based both on symptoms for COVID-19 
and on RT-PCR detection of SARS-CoV-2 from samples collected within 72 hours of the study 
participant reporting symptoms meeting the definition of COVID-19. Participants who are 
hospitalized for COVID-19 without the opportunity for a clinic or home visit will also be 
considered cases, assuming that the symptomatology criteria for COVID-19 are met and a 
respiratory sample is positive for SARS-CoV-2 by PCR at a CLIA-certified or CLIA-certified 
waiver laboratory. Investigators are encouraged to try to obtain a respiratory sample during the 
course of hospitalization for submission to the study central laboratory, if feasible. The investigator 
should determine if the criteria for severe COVID-19 has been met. 
Evidence of severe COVID-19 is defined as in Section 8.1.1. 
All clinical findings will be recorded in the eCRF. All confirmed cases of COVID-19 will be 
captured as MAAEs, along with relevant concomitant medications and details about severity, 
seriousness, and outcome. 
8.1.3. 
Convalescent Period Starting With the Illness Visit 
All study participants who experience COVID-19 symptoms and subsequently present for an 
Illness Visit (in-clinic or at home) will be given an instruction card listing symptoms and severity 
grading system, a thermometer, an oxygen saturation monitor, and saliva collection tubes. 
Participants will be trained on the use of the oxygen saturation monitor and how to take saliva 

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specimens. The list of symptoms is presented in Section 8.1.2 and the severity scoring system is 
presented in Table 3. 
Table 3: 
Grading of COVID-19 Symptoms 
Grading  
All Symptoms 
For Nausea/Vomiting 
ONLY 
For Sense of Smell/Taste 
ONLY 
None 
No symptom 
 
 
Mild 
I had the symptom, but I 
could still do my normal 
activities. 
I was able to eat and drink 
normally. 
I had the symptom, but I 
retained some taste/smell. 
Moderate 
The symptom really 
bothered me. It was hard to 
do my normal activities. 
It bothered me enough that 
I did not eat or drink 
normally. 
My taste/smell was 
significantly affected. 
Severe 
The symptom was very bad. 
I was not able to do 
activities that I usually do. 
I could not eat or drink. 
I have no taste or smell. 
Abbreviation: COVID-19 = coronavirus disease 2019. 
 
The initial Illness Visit is considered Day 1 for the Convalescent Period. Starting on Day 2 of the 
Convalescent Period, the investigator (or medically qualified staff appropriately delegated by the 
investigator) will contact participants daily with telemedicine visits through Day 14 (from the 
Illness Visit or initial COVID-19 contact) or until symptoms have resolved, whichever is later, and 
which may include symptoms persisting longer than the 28-day Convalescent Period (with the 
exception of mild loss of sense of taste/smell).  
If a participant is completely asymptomatic for 72 hours prior to Day 14, including normal oxygen 
saturation and temperature, then telemedicine calls can be reduced to weekly; however, the 
participant should still report the daily symptoms at that contact. The participant should also report 
their oxygen saturation and temperature measured on the day of the contact, but these need not be 
recorded daily during this reduced frequency monitoring period. If a participant reports a change 
or recurrence of symptoms, daily telemedicine visits should be resumed to the daily schedule. For 
these participants, a final telemedicine visit will occur on Day 14 to determine before symptom 
monitoring can be discontinued.  
If the symptoms persist after Day 60, then telemedicine calls can be reduced to weekly; however, 
the participant should still report the daily sypmptoms at that contact.  
Telemedicine visits may be conducted by videoconference or by audio only (telephone). During 
the telemedicine visit (preferably done in the evening), the participant will be asked to verbally 
report the severity of each symptom and their highest body temperature and lowest oxygen 
saturation for that day, and the investigator will determine if medical attention is required due to 

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worsening of COVID-19 symptoms. The presence and severity of each symptom reported by the 
participant will be noted in the appropriate source document (Table 19). 
During the telemedicine visits, participants will be reminded both to collect their own saliva 
sample on 3, 5, 7, 9, 14, and 21 days after the initial Illness Visit and to return the sample to the 
study site. Immediately upon receipt of a saliva sample, the study site will send it for testing to the 
study central virology laboratory. 
During the telemedicine visits, if the participant has a positive result for SARS-CoV-2 from the 
Day 1 Illness Visit, the participant will continue the Convalescent Period. If the participant has a 
negative result for SARS-CoV-2 from the Day 1 Illness Visit, the participant will exit the 
Convalescent Period, including discontinuation of daily telemedicine visits and collection of saliva 
samples, and will return to their respective study schedule (Table 16, Table 17, Table 18, or 
Table 23). Participants who are pending a central laboratory PCR may exit from the Convalescent 
Period based on a negative PCR result from a CLIA-certified or CLIA-certified waiver local 
laboratory, at the investigator’s discretion. However, if the central laboratory PCR results are 
positive after exit from the Convalescent Period, the Convalescent Period must resume.  
All participants confirmed to be COVID-19 cases will be scheduled for a Convalescent Visit (study 
site or home visit) 28 days after the initial Illness Visit. At this visit, a saliva sample will be 
collected and a blood sample will be drawn for immunologic assessment of SARS-CoV-2 infection 
(Table 19). 
If the participant is hospitalized, medically qualified site personnel will try to obtain medical 
records and SARS-CoV-2 diagnostic results and document if the criteria for COVID-19 or severe 
COVID-19 have been met. If the participant is later discharged from the hospital during the 28-day 
period following diagnosis of COVID-19, the study site personnel will arrange for a resumption 
of a schedule for telemedicine visits and sampling for the remainder of the Convalescent Period, 
followed by a return to their respective study schedule (Table 16, Table 17, Table 18, or Table 23). 
8.1.4. 
Ancillary Supplies for Participant Use 
Study sites will distribute Sponsor-provided oral thermometers and rulers for use by participants 
in assessing body temperature and injection site reactions for recording solicited ARs in eDiaries 
(Section 8.2.2). Based on availability, smartphone devices may be provided to those participants 
who do not have their own device to use for eDiary activities. 
Participants will also receive the following Sponsor-provided supplies at Illness Visits where 
COVID-19 is suspected: 
• An instruction card listing symptoms and severity grading system 
• A pulse oximeter for measuring oxygen saturation 

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• Saliva collection tubes and instructions/means for returning saliva samples collected at 
home to the study site 
• Additional oral thermometer, if required. 
8.1.5. 
Immunogenicity Assessments 
Blood samples for immunogenicity assessments will be collected at the timepoints indicated in the 
SoEs (Section 11.1) and in Table 4. Blood samples for immunogenicity assessment will be 
collected before administration of IP. The following analytes will be measured: 
• Serum bAb levels against SARS-CoV-2 as measured by ligand-binding assay specific to 
the SARS-CoV-2 S protein 
• Serum bAb levels against SARS-CoV-2 as measured by ligand-binding assay specific to 
the SARS-CoV-2 nucleocapsid protein 
• Serum nAb titer against SARS-CoV-2 as measured by pseudovirus and/or live virus 
neutralization assays 
Serum will be tested using the ligand-binding assay specific to the SARS-CoV-2 nucleocapsid to 
determine the immunologic status of study participants at baseline and assess for seroconversion 
due to infection during the course of the study. Serum from a subset of participants will be tested 
in the other assays. The selection of the subset and timepoints to be tested will be described in the 
statistical analysis plan (SAP). Sample aliquots will be designed to ensure that backup samples are 
available and that adequate vial volumes may allow for further testing. The actual time and date 
of each sample collected will be recorded in the eCRF, and unique sample identification will be 
used to maintain the blind at the laboratory at all times and to allow for automated sample tracking 
and storage. Handling and preparation of the samples for analysis, as well as shipping and storage 
requirements, will be provided in a separate study manual. 
The ligand-binding assay and measurement of nAb titers will be performed in laboratories 
designated by the Sponsor. 
8.2. 
Safety Assessments 
Safety assessments will include monitoring and recording of the following for each participant: 
• Solicited local and systemic ARs (Section 8.3.5) that occur during the 7 days following 
each injection (ie, the day of dosing and 6 subsequent days). Solicited ARs will be 
recorded daily using eDiaries (Section 8.2.2) (Part A). 
• Unsolicited AEs observed or reported during the 28 days following each injection (ie, the 
day of injection and 27 subsequent days) (Part A [all participants] and Part C [only those 

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who receive the BD]). Unsolicited AEs are AEs that are not included in the 
protocol-defined solicited ARs (Section 8.3.5). 
• AEs leading to discontinuation from dosing and/or study participation from Day 1 
through Day 759 or withdrawal from the study. 
• MAAEs from Day 1 through Day 759 or withdrawal from the study. 
• SAEs from Day 1 through Day 759 or withdrawal from the study. 
• AEs of special interest (AESIs; for participants who receive the BD in Part C) from 
BD-Day 1 through Day 759 or withdrawal from the study. 
• Abnormal vital sign measurements. 
• Physical examination findings. 
• Pregnancy and accompanying outcomes. 
• Concomitant medications and non-study vaccinations. 
8.2.1. 
Safety Phone Calls 
A safety phone call is a telephone call made to the participant by medically qualified study staff. 
Medically qualified staff are those appropriately delegated individuals who are permitted to elicit 
verbal medical history from participants based on local regulations and local licensing 
requirements. 
This call will follow a script, which will facilitate the collection of relevant safety information. 
The participant will be interviewed according to the script about occurrence of unsolicited AEs, 
MAAEs, SAEs, or AEs leading to study withdrawal and concomitant medications associated with 
those events, receipt of any non-study vaccinations, and pregnancy. Occurrence of AEs will only 
be collected by safety phone call during the Vaccination Phase (Table 16, Table 21, and Table 23). 
The timing of the safety phone calls and the relevant safety information collected is provided in 
the SoEs (Section 11.1). 
All safety information described by the participant must be documented in source documents and 
not documented on the script used for the safety telephone contact. All AEs, MAAEs, SAEs, and 
AEs leading to study withdrawal must be recorded in the eCRF as specified in Section 8.3.7. 
8.2.2. 
Use of Electronic Diaries 
In Part A, the Blinded Phase of the study, at the time of consent, the participants must confirm 
they will be willing to complete an eDiary (for 7-day reactogenicity and to surveil weekly for 
COVID-19 symptoms) using either an application downloaded to their smartphone or using a 

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device that is provided at the time of enrollment. This study will utilize the Medidata Patient Cloud 
Application as the eDiary for both collection of 7-day reactogenicity and weekly eDiary prompts 
to elicit an unscheduled Illness Visit if the participant is experiencing COVID-19 symptoms. This 
application allows for real-time data collection on a 21 CFR Part 11 compliant system directly 
from participants. 
In Part A, the Blinded Phase of the study, before enrollment on Day 1, the participant will be 
instructed to download the eDiary application on their personal smartphone or will be provided a 
Sponsor-provisioned device to record solicited ARs (Section 8.3.5) and also to be utilized for 
eDiary prompts through the COVID-19 surveillance period. 
In Part A, the Blinded Phase of the study, at each dosing visit, participants will record data into 
the eDiary starting approximately 30 minutes after dosing under supervision of the study site staff 
to ensure successful entry of assessments. The 30-minute assessment is an opportunity for site staff 
to train the participant. The site staff will perform any retraining as necessary. Study participants 
will continue to record data in an eDiary after they leave the study site, preferably in the evening 
and at the same time each day, on the day of dosing and for 6 days following dosing. 
In Part A, the Blinded Phase of the study, the following local ARs will be solicited by the eDiary: 
pain at injection site, erythema (redness) at injection site, swelling/induration (hardness) at 
injection site, and localized axillary swelling or tenderness ipsilateral to the injection arm. The 
following systemic ARs will be solicited by the eDiary: headache, fatigue, myalgia (muscle aches 
all over the body), arthralgia (aching in several joints), nausea/vomiting, body temperature 
(potentially fever), and chills. 
In Part A, the Blinded Phase of the study, solicited local and systemic reactogenicity ARs, as 
defined in Section 8.3.5, will be collected on the day of each IP injection and during the 7 days 
after IP injection (ie, the day of dosing and 6 subsequent days). Any solicited AR that is ongoing 
beyond Day 7 will be reported in an eDiary until resolution. Adverse reactions recorded in diaries 
beyond Day 7 should be reviewed by study site staff either during the next scheduled phone call 
or at the next study site visit (Table 16). 
If eDiary prompts result in identification of relevant safety events according to the study period or 
symptoms of COVID-19, a follow-up safety call will be triggered.  
In Part A, the Blinded Phase of the study, at each dosing visit, participants will be instructed or 
reminded on thermometer usage to measure body temperature, ruler usage to measure injection 
site erythema and swelling/induration (hardness), and self-assessment for localized axillary 
swelling or tenderness on the same side as the injection arm. 

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In Part A, the Blinded Phase of the study, daily oral body temperature measurement should be 
performed at approximately the same time each day using the thermometer provided by the study 
site. 
Surveillance for signs and symptoms of COVID-19 will start at Part A Day 1 and continue weekly 
through the entire Surveillance Phase of the study (Table 17 and Table 18). After participants 
complete Part A Vaccination Phase of the Study (Table 16 and Table 21), the weekly eDiary Safety 
Follow-up prompts will be triggered on Day 61 (Table 17). The weekly eDiary prompts will utilize 
the same Medidata Patient Cloud Application. Each week (ie, every 7 days) the participant will 
receive a prompt on their smartphone device to regularly surveil for signs and symptoms of 
COVID-19 and any other changes in health status. The participant will be trained on how to 
complete the weekly eDiary prompts at the Part A Day 57 clinic visit and also reminded to call the 
site immediately if they experience any COVID-19 symptoms. The weekly eDiary prompt will 
inquire about the following: 
• Changes in health since the last time completing the weekly eDiary prompt or the last 
contact with the study staff 
• Any known exposure to someone with SARS-CoV-2 infection or COVID-19 since the last 
time completing the weekly eDiary prompt or the last contact with the study staff 
• Capture of any COVID-19 symptoms currently being experienced or experienced since the 
last time completing the weekly check-in as defined in Section 8.1.2 
• Any contact with a healthcare provider that may indicate an MAAE. 
A positive response by the participant to these prompts will result in a notification to both the 
participant and study staff to arrange a call. A follow-up safety call will be performed to the 
participant to determine if an unscheduled Illness Visit for the participant should be arranged as 
defined in Section 8.1.2. The results of the safety call should be recorded in the appropriate source 
documentation. 
If a participant does not respond to the weekly eDiary within a 2-day window around the scheduled 
timepoint, study staff will follow up directly with the participant via phone call or text to confirm 
their health status and to remind the participant of the importance of maintaining weekly contact 
via the eDiary prompt. 
In addition, there will be an eDiary prompt to solicit the collection of information regarding 
participant’s history of facial injections or dermal fillers, for cosmetic or medical indications such 
as migraine headaches.  

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8.2.3. 
Demographics/Medical History 
Demographic information relating to the participant’s sex, age, and race will be recorded at 
Screening on the appropriate eCRF page. 
Additionally, information regarding participant occupational circumstances (eg, essential worker 
status) will be collected at Screening. 
Medical history of each participant, including risk factors for severe COVID-19 as defined in 
Section 6.2.1.1, will be collected and recorded on the Medical History eCRF page. Significant 
findings that were present prior to the signature of the informed consent will also be included in 
the Medical History eCRF page. 
Study participants will also be asked to report history of receipt of seasonal influenza vaccine 
during the current influenza season (typically October through April in the Northern Hemisphere) 
as a concomitant medication. 
8.2.4. 
Physical Examination 
A full physical examination, including vital signs, height, and weight, will be performed at 
Screening and on Day 1, and symptom-directed physical examinations at other scheduled 
timepoints as indicated in the SoEs (Section 11.1). The full examination will include assessment 
of skin, head, ears, eyes, nose, throat, neck, thyroid, lungs, heart, cardiovascular, abdomen, lymph 
nodes, and musculoskeletal system/extremities. Symptom-directed physical examinations may be 
performed at other timepoints at the discretion of the investigator. 
On each dosing day before injection, the arm receiving the injection should be examined and the 
associated lymph nodes should be evaluated. 
Body mass index will be calculated at the Screening Visit (Day 0). 
Any clinically significant finding identified during a study visit after the first dose should be 
reported as an MAAE. 
Significant new findings that begin or worsen after informed consent must be recorded on the AE 
eCRF page. 
8.2.5. 
Vital Sign Measurements 
Vital signs will be measured at the timepoints indicated in the SoEs (Section 11.1). The participant 
will be seated for at least 5 minutes before all measurements are taken. On Day 1 and Day 29, vital 
sign measurements will be collected once before IP injection and at least 30 minutes after IP 
injection (before participants are discharged from the study site). When applicable, vital sign 
measurements should be performed before blood collection.  

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Febrile participants at Day 1 and Day 29 visits (fever is defined as a body temperature 
≥ 38.0°C/100.4°F) may be rescheduled within the relevant window periods. Criteria for delay of 
study treatment are provided in Section 7.1. Afebrile participants with minor illnesses may be 
injected at the discretion of the investigator. 
If any of the vital sign measurements meet the toxicity grading criteria for clinical abnormalities 
of Grade 3 or greater, the abnormal value and grade will be documented on the AE page of the 
eCRF (unless there is another known cause of the abnormality that would result in an AE 
classification). The investigator will continue to monitor the participant with additional 
assessments until the vital sign value has reached the reference range, returns to the vital sign value 
at baseline, is considered stable, or until the investigator determines that follow-up is no longer 
medically necessary. 
8.2.6. 
Blood Sampling  
The maximum planned volumes of blood sampled for immunogenicity analyses per participant are 
approximately 50 mL for 1 day, 100 mL for 28 days (Table 16), and 300 to 420 mL (dependent on 
participation in Part B and Part C) for the total study volume (Table 4). 
Table 4: 
Maximum Planned Immunogenicity Blood Sampling Volumes per 
Participant by Visit 
Study Visit 
Day 
Table 16 
D1 
Table 16 
D29 
Table 16 
D57 
Table 17 
D209 
Table 17 
D394 
Table 18 
D759 
Total 
Immunogenicity 
blood samples a 
50 mL 
50 mL 
50 mL 
50 mL 
50 mL 
50 mL 
300 mL 
Study Visit Day 
Part B 
Day 1b 
Part B 
Day 29b 
Part B 
Day 57b 
NA 
NA 
NA 
NA 
Immunogenicity 
blood samples a 
20 mL 
20 mL 
20 mL 
NA 
NA 
NA 
60 mLc 
Study Visit Day 
Part C 
Day 1d 
Part C 
Day 4d 
Part C 
Day 29d 
Part C 
Day 181d 
NA 
NA 
NA 
Immunogenicity 
blood samples a 
24 mL 
8 mL 
24 mL 
24 mL 
NA 
NA 
80 mL 
Abbreviations: COVID-19 = coronavirus disease 2019; D = Day; NA = not applicable; RT-PCR = reverse transcriptase 
polymerase chain reaction; OL = open-label; SoE = schedule of events. 
a 
Additional blood samples (16 mL) will be taken at Illness Day 1 and Convalescent Visit Day 28 for those 
participants who report symptoms of COVID-19 and who have RT-PCR confirmed symptomatic COVID-19, 
respectively. 
b 
If a visit from SoE Table 16 and Table 17 and a Part B visit overlap, only the Part B sample will be taken (using 
the Part B kit). The exception would be if an Illness Day 1 or Convalescent Visit Day 28 overlapped with a Part 
B visit. In this case the Illness and Convalescent Visit Day 28 samples would be taken and the corresponding kits 
used. 

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c 
For participants who received placebo during the Part A Blinded Phase and receive mRNA-1273 during Part B. 
Note that immunogenicity blood samples are collected only on OL-D1 and OL-D57 (Table 21) or OL-D1 and 
OL-D29 (Table 22) in Part B. 
d 
If a visit from SoE Table 17 and Table 18 and a Part C visit overlap, only the Part C sample will be taken (using 
the Part C kit). Exceptions would be if an Illness Day 1 or Convalescent Visit Day 28 overlapped with a Part C 
visit, in this case the Illness and Convalescent Visit Day 28 samples would be taken and corresponding kits used, 
or in the case of a Part C Day 4 visit, both sets of samples would need to be taken using both kits. 
8.3. 
Safety Definitions and Procedures 
8.3.1. 
Adverse Event 
An AE is defined as any untoward medical occurrence associated with the use of a drug in humans, 
whether or not considered drug related. 
A treatment-emergent AE (TEAE) is defined as any event not present before exposure to IP or any 
event already present that worsens in intensity or frequency after exposure. 
Events Meeting the Adverse Event Definition 
• Exacerbation of a chronic or intermittent pre-existing condition including either an 
increase in frequency and/or intensity of the condition. 
• New conditions detected or diagnosed after the first dose of IP even though they may 
have been present before the start of the study. 
Events NOT Meeting the Adverse Event Definition 
• Medical or surgical procedure (eg, endoscopy, appendectomy): the condition that leads to 
the procedure should be the AE. 
• Situations in which an untoward medical occurrence did not occur (social and/or 
convenience admission to a hospital). 
An AR is any AE for which there is a reasonable possibility that the IP caused the AE 
(Section 8.3.5). For the purposes of investigational new drug safety reporting, “reasonable 
possibility” means that there is evidence to suggest a causal relationship between the IP and the 
AE. 
An unsolicited AE is any AE reported by the participant that is not specified as a solicited AR in 
the protocol; or is specified as a solicited AR in the protocol, but starts outside the protocol-defined 
period for reporting solicited ARs (ie, for the 7 days after each dose of IP, Part A, Blinded Phase 
only). 
8.3.2. 
Medically Attended Adverse Events 
An MAAE is an AE that leads to an unscheduled visit (including a telemedicine visit) to a 
healthcare practitioner (HCP). This would include visits to a study site for unscheduled 

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assessments (eg, rash assessment, abnormal laboratory follow-up, COVID-19 [Section 8.1.1]) and 
visits to HCPs external to the study site (eg, urgent care, primary care physician). Investigators 
will review unsolicited AEs for the occurrence of any MAAEs. All MAAEs must be fully reported 
on the MAAE page of the eCRF. 
8.3.2.1. 
Anaphylaxis 
All suspected cases of anaphylaxis should be recorded as MAAEs and reported as an SAE, based 
on criteria for a medically important event, unless the event meets other serious criteria. As an 
SAE, the event should be reported to the Sponsor or designee immediately and in all circumstances 
within 24 hours as per Section 8.3.12 (Reporting SAEs). The investigator will submit any updated 
anaphylaxis case data to the Sponsor within 24 hours of it being available. For reporting purposes, 
a participant who displays signs/symptoms consistent with anaphylaxis as shown below should be 
reported as a potential case of anaphylaxis. This is provided as general guidance for investigators 
and is based on the Brighton Collaboration case definition (Rüggeberg et al 2007).  
Anaphylaxis is an acute hypersensitivity reaction with multi-organ system involvement that can 
present as, or rapidly progress to, a severe life-threatening reaction. It may occur following 
exposure to allergens from a variety of sources. Anaphylaxis is a clinical syndrome characterized 
by:  
• Sudden onset AND 
• Rapid progression of signs and symptoms AND 
• Involving 2 or more organ systems, as follows:  
- 
Skin/mucosal: urticaria (hives), generalized erythema, angioedema, generalized 
pruritus with skin rash, generalized prickle sensation, red and itchy eyes 
- 
Cardiovascular: measured hypotension, clinical diagnosis of uncompensated 
shock, loss of consciousness or decreased level of consciousness, evidence of 
reduced peripheral circulation 
- 
Respiratory: bilateral wheeze (bronchospasm), difficulty breathing, stridor, upper 
airway swelling (lip, tongue, throat, uvula, or larynx), respiratory distress, 
persistent dry cough, hoarse voice, sensation of throat closure, sneezing, rhinorrhea 
- 
Gastrointestinal: diarrhea, abdominal pain, nausea, vomiting 
8.3.3. 
Adverse Events of Special Interest 
An AESI is a serious or nonserious AE of scientific and medical concern specific to the Sponsor’s 
product or program, for which ongoing monitoring and immediate notification by the investigator 
to the Sponsor is required and documentation is in the form of a case narrative. Such events may 

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require further investigation to characterize and understand them. Refer to Section 11.5 for a list 
of AESIs pertinent to this study. All AESIs will be collected for participants receiving the BD in 
Part C through the remaining study period and must be reported to the Sponsor or designee 
immediately and in all circumstances within 24 hours of becoming aware of the event via the 
electronic data capture system. If a site receives a report of a new AESI from a study participant 
or receives updated data on a previously reported AESI, and the eCRF has been taken offline, then 
the site can report this information on a paper AESI form using the SAE Mailbox, the SAE Hotline, 
or the SAE Fax line (Section 8.3.11). 
Acute Myocarditis and/or Pericarditis 
These definitions are intended to serve as a guide to help in the reporting of suspected cases of 
myocarditis and/or pericarditis; however, the diagnosis of suspected cases is left to the 
investigator’s clinical judgement. 
All suspected cases of probable and confirmed myocarditis, pericarditis, or myopericarditis should 
be recorded as an AESI, and reported as an SAE, if the event meets seriousness criteria. As an 
SAE, the event should be reported to the Sponsor or designee immediately and in all circumstances 
within 24 hours as per Section 8.3.11. The investigator will submit any updated myocarditis, 
pericarditis, or myopericarditis case data to the Sponsor within 24 hours of it being available. For 
reporting purposes, a participant who displays signs/symptoms consistent with the CDC case 
definitions as described below (Gargano et al 2021), should be reported as a potential case of 
confirmed or probable myocarditis, pericarditis, or myopericarditis. 
Acute Myocarditis Case Definition 
Presence of ≥ 1 new or worsening of the following clinical symptoms (persons who lack the listed 
symptoms but who meet other criteria may be classified as subclinical myocarditis [probable or 
confirmed]): 
• Chest pain/pressure/discomfort 
• Dyspnea/shortness of breath/pain with breathing 
• Palpitations 
• Syncope 
AND 
For PROBABLE CASE: 
Presence of ≥ 1 new finding of the following: 
• Troponin level above upper limit of normal (any type of troponin) 

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• Abnormal electrocardiogram (ECG or EKG) or rhythm monitoring findings consistent 
with myocarditis 
o To meet the ECG or rhythm monitoring criterion, a probable case must include at 
least 1 of the following: 
▪ ST segment or T-wave abnormalities 
▪ Paroxysmal or sustained atrial, supraventricular, or ventricular arrhythmias 
▪ AV nodal conduction delays or intraventricular conduction defects 
• Abnormal cardiac function or wall motion abnormalities on echocardiogram 
• Cardiac magnetic resonance imaging (cMRI) finding consistent with myocarditis 
(Ferreira et al 2018) 
AND 
• No other identifiable cause of the symptoms and findings 
For CONFIRMED CASE: 
• Histopathologic confirmation of myocarditis (using Dallas criteria [Aretz et al 1987]) 
OR 
• cMRI findings consistent with myocarditis in the presence of troponin level above 
upper limit of normal (any type of troponin) 
AND 
• No other identifiable cause of the symptoms and findings 
Acute Pericarditis Case Definition 
Presence of ≥ 2 new or worsening of the following clinical features (Adler et al 2015): 
• Acute chest pain (Typically described as pain made worse by lying down, deep 
inspiration, or cough; and relieved by sitting up or leaning forward, although other 
types of chest pain may occur) 
• Pericardial rub on examination 
• New ST-elevation or PR-depression on EKG 
• New or worsening pericardial effusion on echocardiogram or magnetic resonance 
imaging 
Myopericarditis Case Definition 

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Participants who meet criteria for both myocarditis and pericarditis may be described under 
myopericarditis. 
8.3.4. 
Serious Adverse Events 
An AE (including an AR) is considered an SAE if, in the view of either the investigator or Sponsor, 
it results in any of the following outcomes: 
• Death 
A death that occurs during the study or that comes to the attention of the investigator 
during the protocol-defined follow-up period must be reported to the Sponsor, whether or 
not it is considered related to IP. 
• Is life-threatening  
An AE is considered life-threatening if, in the view of either the investigator or the 
Sponsor, its occurrence places the participant at immediate risk of death. It does not 
include an AE that, had it occurred in a more severe form, might have caused death. 
• Inpatient hospitalization or prolongation of existing hospitalization 
In general, inpatient hospitalization indicates the participant was admitted to the hospital 
or emergency ward for at least one overnight stay for observation and/or treatment that 
would not have been appropriate in the physician’s office or outpatient setting. The 
hospital or emergency ward admission should be considered an SAE regardless of 
whether opinions differ as to the necessity of the admission. Complications that occur 
during inpatient hospitalization will be recorded as an AE; however, if a complication/AE 
prolongs hospitalization or otherwise fulfills SAE criteria, the complication/AE will be 
recorded as a separate SAE. 
• Persistent or significant incapacity or substantial disruption of the ability to conduct 
normal life functions 
This definition is not intended to include experiences of relatively minor medical 
significance such as uncomplicated headache, nausea/vomiting, diarrhea, influenza, and 
accidental trauma (eg, sprained ankle) which may interfere with or prevent everyday life 
functions but do not constitute a substantial disruption. 
• Congenital anomaly or birth defect 
• Medically important event 
Medical judgment should be exercised in deciding whether SAE reporting is appropriate 
in other situations, such as important medical events that may not be immediately 
life-threatening or result in death or hospitalization but may jeopardize the participant or 
require medical or surgical intervention to prevent one of the other outcomes listed in the 

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above definition. These events should usually be considered serious. Examples of such 
medical events include allergic bronchospasm requiring intensive treatment in an 
emergency room or at home, blood dyscrasias or convulsions that do not result in 
inpatient hospitalization, or the development of drug dependency or drug abuse. 
8.3.5. 
Solicited Adverse Reactions (Part A) 
The term “reactogenicity” refers to the occurrence and intensity of selected signs and symptoms 
(ARs) occurring after IP injection. The eDiary will solicit daily participant reporting of ARs using 
a structured checklist (Section 8.2.2). Participants will record such occurrences in an eDiary on the 
day of IP injection and for the 6 days after the day of dosing. 
Severity grading of reactogenicity will occur automatically based on participant entry into the 
eDiary according to the grading scales presented in Table 5 modified from the Toxicity Grading 
Scale for Healthy Adult and Adolescent Volunteers Enrolled in Preventative Vaccine Clinical 
Trials (DHHS 2007). 
If a solicited local or systemic AR continues beyond 7 days after dosing, the participant will be 
prompted daily to capture solicited local or systemic AR in the eDiary until resolution. Adverse 
reactions recorded in eDiaries beyond Day 7 should be reviewed by the investigator either via 
phone call or at the following study visit. All solicited ARs (local and systemic) will be considered 
causally related to dosing.

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Table 5: 
Solicited Adverse Reactions and Grades 
Reaction 
Grade 0 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Injection site pain 
None 
Does not interfere 
with activity  
Repeated use of 
over-the-counter pain reliever 
> 24 hours or interferes with 
activity  
Any use of 
prescription pain 
reliever or prevents 
daily activity 
Requires emergency room visit 
or hospitalization 
Injection site erythema 
(redness) 
< 25 mm/ 
< 2.5 cm 
25 – 50 mm/ 
2.5 – 5 cm 
51 – 100 mm/ 
5.1 – 10 cm 
> 100 mm/ 
> 10 cm 
Necrosis or exfoliative dermatitis 
Injection site 
swelling/induration 
(hardness) 
< 25 mm/ 
< 2.5 cm 
25 – 50 mm/ 
2.5 – 5 cm 
51 – 100 mm/ 
5.1 – 10 cm  
> 100 mm/ 
> 10 cm 
Necrosis  
Axillary (underarm) 
swelling or tenderness 
ipsilateral to the side of 
injection 
None 
No interference 
with activity 
Repeated use of 
over-the-counter 
(non-narcotic) pain reliever 
> 24 hours or some 
interference with activity 
Any use of 
prescription (narcotic) 
pain reliever or 
prevents daily activity 
Emergency room visit or 
hospitalization 
Headache 
None 
No interference 
with activity 
Repeated use of 
over-the-counter pain reliever 
> 24 hours or some 
interference with activity 
Significant; any use 
of prescription pain 
reliever or prevents 
daily activity 
Requires emergency room visit 
or hospitalization 
Fatigue 
None 
No interference 
with activity  
Some interference with 
activity 
Significant; prevents 
daily activity  
Requires emergency room visit 
or hospitalization 
Myalgia (muscle aches all 
over body) 
None 
No interference 
with activity  
Some interference with 
activity 
Significant; prevents 
daily activity  
Requires emergency room visit 
or hospitalization 
Arthralgia (joint aches in 
several joints) 
None 
No interference 
with activity  
Some interference with 
activity 
Significant; prevents 
daily activity  
Requires emergency room visit 
or hospitalization 

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Reaction 
Grade 0 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Nausea/vomiting 
None 
No interference 
with activity or 
1-2 episodes/ 
24 hours 
Some interference with 
activity or 
> 2 episodes/24 hours 
Prevents daily 
activity, requires 
outpatient intravenous 
hydration 
Requires emergency room visit 
or hospitalization for 
hypotensive shock 
Chills 
None 
No interference 
with activity 
Some interference with 
activity not requiring medical 
intervention 
Prevents daily activity 
and requires medical 
intervention 
Requires emergency room visit 
or hospitalization 
Fever (oral) 
< 38.0°C 
< 100.4°F 
38.0 – 38.4°C 
100.4 – 101.1°F 
38.5 – 38.9°C 
101.2 – 102.0°F 
39.0 – 40.0°C 
102.1 – 104.0°F 
> 40.0°C 
> 104.0°F 

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Any solicited AR that meets any of the following criteria must be entered into the 
participant’s source document and must also be recorded as an AE in the participant’s 
Adverse Event eCRF: 
• Solicited local or systemic AR that results in a visit to an HCP (MAAE) 
• Solicited local or systemic AR leading to the participant withdrawing from the study or 
the participant being withdrawn from the study by the investigator (AE leading to 
withdrawal) 
• Solicited local or systemic AR lasting beyond 7 days post injection 
• Solicited local or systemic AR that leads to participant withdrawal from IP 
• Solicited local or systemic AR that otherwise meets the definition of an SAE 
8.3.6. 
Recording and Follow-up of Pregnancy 
Female participants who have a positive pregnancy test at Screening should not be enrolled; 
participants who have a positive pregnancy test any time during the study should receive no further 
dosing with IP but should be asked to remain in the study and be followed-up for safety. Pregnancy 
testing is scheduled to occur at Screening, Blinded and OL Day 1, Blinded and OL Day 29, and 
Part C BD-Day 1 (Table 16, Table 21, Table 22, and Table 23). 
Details of all pregnancies in female participants will be collected after the start of study treatment 
and until Day 759. 
• If a pregnancy is reported, the investigator should inform the Sponsor within 24 hours of 
learning of the pregnancy and should follow the procedures outlined in this section. 
• Abnormal pregnancy outcomes (eg, spontaneous abortion, fetal death, stillbirth, 
congenital anomalies, ectopic pregnancy) are considered SAEs. 
Pregnancies occurring in participants after enrollment must be reported to Sponsor or designee 
within 24 hours of the site learning of its occurrence. If the participant agrees to submit this 
information, the pregnancy must be followed to determine the outcome, including spontaneous or 
voluntary termination, details of the birth, and the presence or absence of any birth defects, 
congenital abnormalities, or maternal and/or newborn complications. This follow-up should occur 
even if intended duration of the safety follow-up for the study has ended. Pregnancy report forms 
will be distributed to the study site to be used for this purpose. The investigator must immediately 
(within 24 hours of awareness) report to the Sponsor any pregnancy resulting in an abnormal 
outcome according to the procedures described for SAEs. 

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8.3.7. 
Recording and Follow-up of an AE and/or SAE 
The investigator is responsible for ensuring that all AEs and SAEs are recorded in the eCRF and 
reported to the Sponsor. 
Solicited ARs will be collected from Day 1 through 7 days after each dose (Part A). Other 
(unsolicited) AEs will be collected from Day 1 through 28 days after each dose in Part A (all 
participants) and Part C (only those who receive the BD). 
Both MAAEs and SAEs will be collected from Day 1 throughout the entire study duration 
(Day 759 for all participants), as specified in the SoEs (Table 16, Table 17, Table 18, Table 19, 
Table 21, Table 22, and Table 23). Any AEs occurring before receipt of IP will be analyzed 
separately from TEAEs. 
At every study site visit or telephone contact, participants will be asked a standard question to 
elicit any medically related changes, including surveillance for COVID-19 symptoms, in their 
well-being according to the scripts provided. Participants will also be asked if they have been 
hospitalized, had any accidents, used any new medications, changed concomitant medication 
regimens (both prescription and over-the-counter medications), or had any non-study vaccinations. 
In addition to participant observations, physical examination findings or other documents relevant 
to participant safety classified as an AE will be documented on the AE page of the eCRF. 
After the initial AE/SAE report, the investigator is required to proactively follow each participant 
at subsequent visits/contacts. All AEs and SAEs will be treated as medically appropriate and 
followed until resolution, stabilization, the event is otherwise explained, or the participant is LTFU 
(as defined in Section 7.4). 
8.3.8. 
Time Period and Frequency for Collecting AE and SAE Information 
All confirmed serious COVID-19 cases and SAEs will be recorded and reported to the Sponsor or 
designee immediately and under no circumstance should this exceed 24 hours, as indicated in 
Section 8.3.11. The investigator will submit any updated serious COVID-19 cases and SAE data 
to the Sponsor within 24 hours of it being available. COVID-19 cases are defined in Section 8.1.1. 
Investigators are not obligated to actively seek AEs or SAEs after conclusion of the study 
participation (Day 759). However, if an investigator learns of any SAE, including a death, at any 
time after a participant has been discharged from the study and considers the event to be reasonably 
related to the study IP or study participation, the investigator must promptly notify the Sponsor. 
8.3.9. 
Assessment of Intensity 
An event is defined as “serious” when it meets at least one of the predefined outcomes as described 
in the definition of an SAE (Section 8.3.4), NOT when it is rated as severe. 

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The severity (or intensity) of an AR or AE refers to the extent to which it affects the participant’s 
daily activities. The Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled 
in Preventative Vaccine Clinical Trials (DHHS 2007) will be used to categorize local and systemic 
reactogenicity events (solicited ARs), clinical laboratory test results, and vital sign measurements 
observed during this study. Specific criteria for local and systemic reactogenicity events are 
presented in Section 8.3.55. 
The determination of severity for all unsolicited AEs should be made by the investigator based 
upon medical judgment and the definitions of severity as follows: 
• Mild: These events do not interfere with the participant’s daily activities. 
• Moderate: These events cause some interference with the participant’s daily activities 
and require limited or no medical intervention. 
• Severe: These events prevent the participant’s daily activity and require intensive 
therapeutic intervention. 
Study staff should elicit from the participant the impact of AEs on the participant’s activities of 
daily living to assess severity and document appropriately in the participant’s source 
documentation. Changes in the severity of an AE should be documented in the participant’s source 
documentation to allow an assessment of the duration of the event at each level of intensity to be 
performed. An AE characterized as intermittent requires documentation of onset and duration of 
each episode. An AE that fluctuates in severity during the course of the event is reported once in 
the eCRF at the highest severity observed. 
8.3.10. 
Assessment of Causality 
The investigator’s assessment of an AE’s relationship to IP is part of the documentation process 
but is not a factor in determining what is or is not reported in the study. 
The investigator will assess causality (ie, whether there is a reasonable possibility that the IP 
caused the event) for all AEs and SAEs. The relationship will be characterized using the following 
classification: 
Not related: There is not a reasonable possibility of a relationship to the IP. Participant did not 
receive the IP OR temporal sequence of the AE onset relative to administration of the IP is not 
reasonable OR the AE is more likely explained by another cause than the IP. 
Related: There is a reasonable possibility of a relationship to the IP. There is evidence of exposure 
to the IP. The temporal sequence of the AE onset relative to the administration of the IP is 
reasonable. The AE is more likely explained by the IP than by another cause. 

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8.3.11. 
Reporting Adverse Events 
The investigator is responsible for reporting all AEs that are observed or reported during the study, 
regardless of their relationship to IP or their clinical significance. If there is any doubt as to whether 
a clinical observation is an AE, the event should be reported. 
All unsolicited AEs reported or observed during the study will be recorded on the AE page of the 
eCRF. Information to be collected includes, type of event, time of onset, investigator-specified 
assessment of severity (impact on activities of daily living) and relationship to IP, time of 
resolution of the event, seriousness, as well as any required treatment or evaluations, and outcome. 
The unsolicited AEs resulting from concurrent illnesses, reactions to concurrent illnesses, reactions 
to concurrent medications, or progression of disease states must also be reported. All AEs will be 
followed until they are resolved or stable or judged by the investigator to be not clinically 
significant. The Medical Dictionary for Regulatory Activities (MedDRA) will be used to code all 
unsolicited AEs. 
Any medical condition that is present at the time that the participant is screened but does not 
deteriorate should not be reported as an unsolicited AE. However, if it deteriorates at any time 
during the study, it should be recorded as an unsolicited AE. 
Any AE or COVID-19 case considered serious by the investigator or that meets SAE criteria 
(Section 8.3.4) must be reported to the Sponsor immediately (within 24 hours of becoming aware 
of the SAE or COVID-19 case). The investigator will assess whether there is a reasonable 
possibility that the IP caused the SAE. The Sponsor will be responsible for notifying the relevant 
regulatory authorities of any SAE as outlined in the 21 US CFR Parts 312 and 320. The investigator 
is responsible for notifying the institutional review board (IRB) directly. 
If the eCRF is unavailable at the time of the SAE, the following contact information is to be used 
for SAE reporting: 
• SAE Mailbox: Safety_Moderna@iqvia.com 
• SAE Hotline (USA and Canada): +1-866-599-1341 
• SAE Fax line (USA and Canada): +1-866-599-1342 
8.3.12. 
Regulatory Reporting Requirements for SAEs 
Prompt notification by the investigator to the Sponsor of a SAE is essential so that legal obligations 
and ethical responsibilities towards the safety of participants and the safety of a study intervention 
under clinical investigation are met. 
The Sponsor has a legal responsibility to notify both the local regulatory authority and other 
regulatory agencies about the safety of a study intervention under clinical investigation. The 

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Sponsor will comply with country-specific regulatory requirements relating to safety reporting to 
the regulatory authority, IRBs, and investigators. 
Investigator safety reports must be prepared for suspected unexpected serious ARs according to 
local regulatory requirements and Sponsor policy and forwarded to investigators as necessary. 
An investigator who receives an investigator safety report describing a SAE or other specific safety 
information (eg, summary or listing of SAEs) from the Sponsor will review and then file it along 
with the IB and will notify the IRB/IEC, if appropriate according to local requirements. 
8.4. 
Monitoring Committees 
8.4.1. 
Protocol Safety Review Team 
A Protocol Safety Review Team (PSRT) will be formed to review interim and cumulative blinded 
(unblinded in Part C) safety data on a regular basis with a remit to escalate concerns to the DSMB 
(DSMB limited to Part A only). The PSRT composition, its remit, and frequency of data review 
will be further defined in a charter.  
8.4.2. 
Data and Safety Monitoring Board 
An independent DSMB will periodically review blinded and unblinded data, including both safety 
and cases of COVID-19 at scheduled data review meetings and at 2 planned IAs. 
• In addition to blinded and unblinded review of safety data, at each data review meeting the 
DSMB will review the numbers and rate of COVID-19 cases, including rate of severe 
COVID disease with prespecified thresholds for imbalance in the treatment groups which 
would trigger halting rules. 
• At the IA, the DSMB will review the IA results and make recommendations to an Oversight 
Group in terms of study results reporting and unblinding based on the boundaries of early 
efficacy as described in Section 9.6 of the protocol. The Oversight Group will be comprised 
of a voting member each from the Sponsor, Biomedical Advance Research and 
Development Authority, and NIAID. 
• The DSMB will monitor the study for non-efficacy at the IA. The boundary for 
non-efficacy is non-binding and will be provided in the DSMB analysis plan. 
• The DSMB will also monitor the study for vaccine harm based on severe COVID-19. 
Continuous harm monitoring will be provided for COVID-19 and severe COVID-19 
separately. For harm monitoring, cases will be counted starting after the first dose of study 
vaccination. Boundaries will be provided based on the exact 1-sided binomial tests 
conditional on the total number of cases under the assumption of VE=0%. If the 
prespecified stopping boundary is reached for either COVID-19 or severe COVID-19, then 

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the unblinded statisticians will immediately inform the DSMB that the harm rules have 
been met. Details will be provided in the DSMB analysis plan. 
• The boundaries are considered guidelines, ie, a recommendation to modify the study would 
not be based solely on statistical rules, as many other factors (ie, totality of the data from 
the study including additional efficacy, safety, and immunogenicity endpoints as well as 
data external to the study) may be part of the decision process. In the case of a 
recommendation to continue the trial regardless of crossing the boundaries for efficacy or 
inefficacy, the reason for disregarding the boundary must be documented in the meeting 
minutes and communicated to the Sponsor. 
After each data review meeting or IA, the DSMB will make a recommendation to the Sponsor 
through an Oversight Group to take one of the following courses of action: 
• Stop further enrollment due to meeting criteria for early efficacy or due to a safety concern. 
• Pause enrollment and consider a change in study design. 
• Continue enrollment and/or study conduct as planned. 
The Sponsor may also request that the DSMB conduct ad hoc reviews of safety events from this 
study or other data, including new nonclinical or clinical information related to mRNA-1273 
external to this study. The DSMB will review all available study data to adjudicate such events in 
accordance with the DSMB charter. 
The DSMB composition, its remit, and frequency of data review will be further defined in the 
DSMB charter and analysis plan. 
8.4.3. 
Adjudication Committee 
An Adjudication Committee (AC) will be assembled for the purpose of reviewing potential cases 
to determine if the criteria for the primary and secondary endpoints have been met. The AC will 
remain blinded to treatment assignment when adjudicating cases for participants whose treatment 
group is still blinded. The AC composition, its remit, and frequency of data review will be further 
defined in a charter. 
8.4.4. 
Independent Cardiac Event Adjudication Committee 
An independent Cardiac Event Adjudication Committee (CEAC) that includes pediatric and adult 
cardiologists will review suspected cases of myocarditis and pericarditis to determine if they meet 
CDC criteria of “probable” or “confirmed” events, and to assess severity (Gargano et al 2021). 
Any cases that the CEAC assesses as representing probable or confirmed cases of myocarditis or 
pericarditis will be referred to the Sponsor, who will then make a final decision on whether to 

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suspend further enrollment and/or study dosing based on an assessment of the overall potential 
risk to study participants. 
The CEAC will operate under the rules of an approved charter that will be written and reviewed 
at the organizational meeting of the CEAC. Details regarding the CEAC composition, 
responsibilities, procedures, and frequency of data review will be defined in its charter. 
8.5. 
Management of Overdose 
As the study treatment is to be administered by a healthcare professional, it is unlikely that an 
overdose will occur. Dose deviations will be tracked as protocol deviations (Section 11.2.8). 
8.6. 
Pharmacokinetics 
Pharmacokinetic parameters are not evaluated in this study. 
8.7. 
Pharmacodynamics 
Pharmacodynamic parameters are not evaluated in this study. 
8.8. 
Exploratory Assessments and Biomarkers 
Exploratory assessments may include assessment of biomarkers for safety, reactogenicity, 
inflammatory and cardiac function. Serologic markers of disease severity, immune response to 
SARS-CoV-2, RT-PCR of NP swab or saliva samples, and genetic sequences of SARS-CoV-2 
strains isolated from participants’ samples may also be measured. 
8.9. 
Medical Resource Utilization and Health Economics 
Medical resource utilization and health economics parameters are not evaluated in this study. 

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9. 
STATISTICAL CONSIDERATIONS 
This section summarizes the planned statistical analysis strategy and procedures for the study, 
focusing on the Blinded Phase of the study (Part A). The details of statistical analysis will be 
provided in the SAP, which will be finalized before the clinical database lock for the study and 
treatment unblinding. If, after the study has begun, but prior to any unblinding, changes are made 
to primary and/or key secondary objectives/hypotheses, or the statistical methods related to those 
hypotheses, then the protocol will be amended (consistent with ICH Guideline E9). Changes to 
other secondary or exploratory analyses made after the protocol has been finalized, along with an 
explanation as to when and why they occurred, will be listed in the SAP or clinical study report 
(CSR) for the study. Ad hoc exploratory analyses, if any, will be clearly identified in the CSR. 
Statistical analysis strategy incorporating the Open-Label Observational Phase (Part B), and to 
assess the BD of mRNA-1273 (Part C) will be provided in the SAP.  
9.1. 
Blinding and Responsibility for Analyses 
Blinding during the Part A, the Blinded Phase of the study will be conducted as described in 
Section 6.2.8. The Sponsor Biostatistics department or designee will generate the randomized 
allocation schedule(s) for study treatment assignment. Randomization will be implemented via an 
IRT. 
Planned interim and primary analyses are described in Section 9.6. Participant-level unblinding 
will be restricted to an independent unblinded statistician and, as needed, a statistical programmer 
performing the IAs, who will have no other responsibilities associated with the study. 
In addition to the routine study monitoring outlined in this protocol, an external DSMB will review 
interim data to safeguard the interests of clinical study participants and to enhancing the integrity 
of the study. The DSMB will review treatment-level results of the IAs, provided by the 
independent unblinded statistician. Limited additional Sponsor personnel may be unblinded to the 
treatment-level results of the IAs, if required, in order to act on the recommendations of the DSMB. 
The extent to which individuals are unblinded with respect to results of IAs will be documented. 
Depending on the recommendation of the DSMB, the Sponsor may prepare a regulatory 
submission after an IA. In this case, pre-identified Sponsor members including the analysis and 
reporting team will be unblinded to treatment assignments and remain unblinded for the remainder 
of the study. Participants and investigators will remain blinded. 
9.2. 
Statistical Hypotheses 
For the primary efficacy objective, the null hypothesis of this study is that the VE of mRNA-1273 
to prevent first occurrence of COVID-19 is ≤ 30% (ie, H0efficacy: VE ≤ 0.3). The study will be 
considered to meet the primary efficacy objective if the corresponding confidence interval (CI) of 
VE rules out 30% at either one of the IAs or at the primary analysis. 

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Vaccine efficacy is defined as the percent reduction in the hazard of the primary endpoint 
(mRNA-1273 vs. placebo). Equivalently, the null hypothesis is: 
H0efficacy: hazard ratio (HR) ≥ 0.7 (equivalently, proportional hazards VE ≤ 0.3). 
A stratified Cox proportional hazard model will be used to assess the magnitude of the treatment 
group difference (ie, HR) between mRNA-1273 and placebo at a 1-sided 0.025 significance level. 
The primary analysis population for efficacy will be the PP Set, defined in Section 9.4. In the 
primary analysis of efficacy, cases will be counted starting 14 days after the second dose of IP. 
Hypothesis testing for immunogenicity is described in Section 9.5.3.2. 
9.3. 
Sample Size Determination 
The sample size is driven by the total number of cases to demonstrate VE (mRNA-1273 vs. 
placebo) to prevent COVID-19 in Part A. Under the assumption of proportional hazards over time 
and with 1:1 randomization of mRNA-1273 and placebo, a total of 151 COVID-19 cases will 
provide 90% power to detect a 60% reduction in hazard rate (60% VE), rejecting the null 
hypothesis H0: VE ≤ 30%, with 2 IAs at 35% and 70% of the target total number of cases using a 
1-sided O’Brien-Fleming boundary for efficacy and a log-rank test statistic with a 1-sided false 
positive error rate of 0.025. The total number of cases pertains to the PP Set accruing at least 
14 days after the second dose. There are 2 planned IAs in this study, which will be performed when 
approximately 35% and 70% of the target total number of cases have been observed. 
Approximately 30,000 participants will be randomized with the following assumptions: 
• The target VE against COVID-19 is 60% (with 95% CI lower bound ruling out 30%, 
rejecting the null hypothesis H0: VE ≤ 30%) 
• A 6-month COVID-19 incidence rate of 0.75% in the placebo arm 
• An annual dropout rate of 2% (loss of evaluable participants) 
• Two IAs at 35% and 70% of total target cases across the 2 treatment groups with 
O’Brien-Fleming boundaries for efficacy monitoring 
• 3-month uniform accrual 
• Approximately 15% of participants will be excluded from the PP population, and 
participants are at risk for COVID-19 starting 14 days after the second dose 
Table 6 provides sample size with 90% power to demonstrate VE on COVID-19. 

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Table 6: 
Conditions and Sample Size to Demonstrate Vaccine Efficacy 
Target VE 
Lower 
Bound 
Randomization 
Ratio 
Total # of 
Cases 
6-Month Incidence Rate 
Total 
Sample 
Sizea 
-- 
-- 
-- 
-- 
Placebo 
mRNA-1273 
-- 
60% 
30% 
1:1 
151 
0.75% 
0.30% 
30,000 
Abbreviations: IP = investigational product; PP = Per Protocol; VE = vaccine efficacy. 
a 
Sample size to account for 15% participants to be excluded from the PP Set (eg, seropositive at baseline, have not 
received planned IP). 
The sample size is calculated using R package gsDesign (Anderson 2020). 
Under these above assumptions including 6-month incidence rate of 0.75% on placebo, with 
30,000 participants, it will take approximately 5, 8, and 10 months from study start (first subject 
first dose), respectively, to accrue 35% (approximately 53), 70% (approximately 106) and 100% 
(151) of the target number of cases in the PP Set. 
Figure 4 shows the power of the primary efficacy endpoint under true VE at the 2 planned IAs and 
the primary efficacy analysis assuming a total of 151 events. 
Figure 4: 
Boundary Crossing Probabilities by Effect Size 
 
The Sponsor may adjust the size of the study or duration of follow-up based on the blinded review 
of the total number of cases of COVID-19 accrued during the study, in addition to estimated 
percentages of study participants with serologic evidence of SARS-CoV-2 infection at baseline. 

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9.3.1. 
Power for Selected Secondary Efficacy Endpoints 
For the secondary objective on VE against virologically confirmed SARS‑CoV‑2 infection or 
COVID‑19 regardless of symptomatology or severity (COV-INF), the study will have ≥ 90% 
power to demonstrate the VE is above 30% (to reject null hypothesis VE ≤ 30%) at 1-sided alpha 
of 2.5% if the true VE to prevent COV-INF is 60% because every COVID-19 endpoint is 
necessarily a COV-INF endpoint. 
For the secondary objective on VE against severe COVID-19, Table 7 provides power of 
demonstrating VE based on a total of 30 and 60 events under different scenarios of true VE and 
VE criteria. 
Table 7: 
Power of Demonstrating Vaccine Efficacy Against Severe COVID-19 
True VE 
Total No. of 
Severe COVID-19 Cases 
Severe COVID-19 (Secondary Objective) 
To Reject Null Hypothesis 
Power 
60% 
30 
VE ≤ 0% 
70.90% 
VE ≤ 10% 
60.30% 
VE ≤ 20% 
47.50% 
70% 
VE ≤ 0% 
> 90% 
VE ≤ 10% 
85.30% 
VE ≤ 20% 
76.60% 
80% 
VE ≤ 0% 
> 90% 
VE ≤ 10% 
> 90% 
VE ≤ 20% 
> 90% 
60% 
60 
VE ≤ 0% 
> 90% 
VE ≤ 10% 
88.10% 
VE ≤ 20% 
76.60% 
70% 
VE ≤ 0% 
> 90% 
VE≤ 10% 
> 90% 
VE≤ 20% 
> 90% 
80% 
VE≤ 0% 
> 90% 
VE≤ 10% 
> 90% 
VE≤ 20% 
> 90% 
Abbreviations: COVID-19 = coronavirus disease 2019; VE = vaccine efficacy. 

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9.4. 
Analysis Populations 
Analysis populations for statistical analyses are Randomization Set, Full Analysis Set (FAS), 
modified Intent-to-Treat (mITT) Set, PP Set, Immunogenicity Subset, Solicited Safety Set, and 
Safety Set, as shown in Table 8. 
Table 8: 
Populations for Analyses 
Population 
Description 
Randomization Set 
All participants who are randomized, regardless of the participants’ 
treatment status in the study.  
Full Analysis Set (FAS)  
All randomized participants who received at least one dose of IP. 
Participants will be analyzed according to the group to which they 
were randomized. 
Modified Intent-to-Treat 
(mITT) Set 
All participants in the FAS who had no immunologic or virologic 
evidence of prior COVID-19 (ie, negative NP swab test at Day 1, 
and/or bAb against SARS-CoV-2 nucleocapsid below LOD or 
LLOQ) at Day 1 before the first dose of IP. 
Participants will be analyzed according to the group to which they 
were randomized. 
Per-protocol (PP) Set  
All participants in the mITT Set who received planned doses of IP per 
schedule and have no major protocol deviations, as determined and 
documented by Sponsor prior to database lock and unblinding, that 
impact critical or key study data. 
Participants will be analyzed according to the group to which they 
were randomized. 
Immunogenicity Subset 
All participants in the FAS who were sampled into a subset for 
characterizing mRNA-1273 immunogenicity and had a valid 
immunogenicity test result prior to the first dose of IP and at least 1 
valid result after the first dose of IP. Participants in the subset who 
had major protocol deviations that impact critical or key 
immunogenicity or study data may be excluded from the 
Immunogenicity Subset. The details of the Immunogenicity Subset 
will be documented prior to analysis of immunogenicity data.  
Solicited Safety Set 
The Solicited Safety Set consists of all randomized participants who 
received at least one dose of IP and contributed any solicited AR data. 
The Solicited Safety Set will be used for the analyses of solicited ARs 
and participants will be included in the treatment group corresponding 
to the IP that they actually received. 
Safety Set 
All randomized participants who received at least one dose of IP. The 
Safety Set will be used for all analyses of safety except for the 
solicited ARs. 
Participants will be included in the treatment group corresponding to 
the IP that they actually received. 
Abbreviations: AR = adverse reaction; bAb = binding antibody; COVID-19 = coronavirus disease 2019; 
IP = investigational 
product; 
LLOQ = lower 
limit 
of 
quantification; 
LOD = limit 
of 
detection; 
NP = nasopharyngeal; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2. 

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9.5. 
Statistical Analyses 
This section provides a summary of the planned statistical analyses of the primary and secondary 
endpoints. 
The overall Type I error rate for the primary endpoint at the IAs and the primary analysis is strictly 
controlled at 2.5% (1-sided) based on the Lan-DeMets O’Brien-Fleming approximation spending 
function (see Section 9.6 for details). The primary efficacy results that will be considered 
statistically significant after consideration of the strategy for controlling the Type I error as 
described in Section 9.6. Statistical significance of the primary efficacy endpoint can be achieved 
at either one of the IAs or at the primary analysis. A sequential/hierarchical testing procedure will 
be used to control Type 1 error rate over the primary efficacy endpoint and the secondary efficacy 
endpoints. Secondary efficacy endpoints will only be tested when the primary efficacy endpoint 
achieves statistical significance. Multiplicity adjustments among the secondary efficacy endpoints 
may be performed for secondary efficacy endpoints, in that case, will be specified in the SAP. 
No formal multiple comparison adjustments will be employed for multiple safety endpoints or 
multiple efficacy endpoints. Nominal p-values and CIs may be computed for other efficacy 
analyses without controlling for multiplicity as a measure of VE. 
9.5.1. 
Efficacy Analyses 
Efficacy analyses will be performed using the FAS, mITT, and PP populations, and participants 
will be included in the treatment group to which they were randomized. The primary analysis 
population will be the PP Set. 
Table 9 summarizes the analysis approach for primary and secondary efficacy endpoints for 
Part A, the randomized, observer-blind, and placebo-controlled phase of the study. Sensitivity 
analysis methods are described for each endpoint as applicable. 
Table 9: 
Statistical Analysis Methods of Efficacy Endpoints 
Endpoint 
Statistical Analysis Methods 
Primary endpoint: 
Vaccine Efficacy (VE) of mRNA-1273 
to prevent COVID-19 
• 
Primary analysis: VE will be estimated with 1 – HR 
(mRNA-1273 vs. placebo) using a Cox proportional 
hazard regression model with treatment group as a fixed 
effect and adjusting for stratification factor based on the 
PP Set, with cases counted starting 14 days after the 
second dose of IP. 
• 
Analysis using the same model based on the mITT Set. 
• 
Sensitivity analysis using the same model based on the 
PP Set, with cases counted starting either immediately 
after the second dose of IP or immediately after the first 
dose of IP. 

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Endpoint 
Statistical Analysis Methods 
• 
Subgroup analysis of the primary efficacy endpoint will 
be performed to assess consistency of VE, such as in the 
age groups ≥ 18 and < 65 years and ≥ 65 years. 
• 
Supportive analysis of VE to be estimated with 1 – ratio 
of incidence rates with 95% CI using the exact method 
conditional upon the total number of cases. 
• 
Supportive analysis of cumulative incidence VE. 
Secondary endpoints: 
• 
Vaccine efficacy of mRNA-1273 
to prevent severe COVID-19 
• 
Vaccine efficacy of mRNA-1273 
to prevent serologically confirmed 
SARS‑CoV‑2 infection or 
COVID‑19 regardless of 
symptomatology or severity 
• 
Vaccine efficacy of mRNA-1273 
to prevent COVID-19 using a 
secondary definition of symptoms 
• 
Vaccine efficacy of mRNA-1273 
to prevent death due to COVID-19 
• 
Vaccine efficacy of mRNA-1273 
to prevent COVID-19 after the 
first dose of IP 
• 
Vaccine efficacy of mRNA-1273 
to prevent asymptomatic 
SARS-CoV-2 infection 
Similar analysis method as for the primary endpoint analysis. 
For each of the secondary endpoints: 
• 
Primary analysis: VE will be estimated with 1 – HR 
(mRNA-1273 vs. placebo) using a Cox proportional 
hazard regression model with treatment group as a 
fixed effect and adjusting for stratification factor 
based on the PP Set, with cases counted starting 
14 days after the second dose of IP. 
• 
Analysis using the same model based on the mITT 
Set. 
• 
Sensitivity analyses with cases counted starting 
immediately after the second dose of IP, 14 days 
after the first dose of IP, immediately after the first 
dose of IP, and immediately after randomization. 
• 
Vaccine efficacy and 95% CI based on the case 
incidence will be estimated with 1 – ratio of 
incidence rates using the exact method conditional 
upon the total number of cases. 
• 
Vaccine efficacy of mRNA-1273 
to prevent COVID-19 in all study 
participants, regardless of evidence 
of prior SARS-CoV-2 infection 
The FAS population will be used for this secondary 
objective, using similar analysis methods as for the primary 
endpoint analysis. 
• 
Primary analysis: VE will be estimated with 1 – HR 
(mRNA-1273 vs. placebo) using a Cox proportional 
hazard regression model with treatment group as a 
fixed effect and adjusting for stratification factor 
based on the FAS, with cases counted starting 
14 days after the second dose of IP. 
• 
Sensitivity analyses with cases counted starting 
immediately after the second dose of IP, 14 days 
after the first dose of IP, immediately after the first 
dose of IP, and immediately after randomization.  
Abbreviations: CI = confidence internval; COVID-19 = coronavirus disease 2019; FAS = Full Analysis Set; 
HR= hazard ratio; IP = investigational product; mITT = modified Intent-to-Treat; PP = Per Protocol; SARS-CoV-
2 = severe acute respiratory syndrome coronavirus 2.  

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9.5.1.1. 
Efficacy Analysis on Primary Endpoint 
To assess the primary efficacy endpoint of VE of mRNA-1273 in preventing the first occurrence 
of COVID-19 from 14 days after second dose of IP, Cox proportional hazards regression will be 
used to estimate proportional hazards VE (PH VE), measured by one minus the HR (mRNA-1273 
vs. placebo), with a 2-sided score-based 95% CI and 2-sided p-value for testing H0: VE ≤ 30%. 
Vaccine efficacy is defined as the percent reduction in the hazard of the primary endpoint 
(mRNA-1273 vs. placebo). The VE will be estimated using one minus the HR (mRNA-1273 vs. 
placebo) estimand. A stratified Cox proportional hazard model will be used to assess the magnitude 
of the treatment group difference (ie, HR) between mRNA-1273 and placebo. The HR and its 95% 
CI from the stratified Cox model with Efron’s method of tie handling and with treatment group as 
covariate will be reported. The same stratification factors used for randomization will be applied 
to the stratified Cox model. 
For the primary efficacy endpoints, participants without documented COVID-19 will be censored 
at the last study assessment date. Potential intercurrent events may include: 1) death unrelated to 
COVID-19 and 2) early COVID-19 up to 14 days after second study dose. 
In the estimand of the primary analysis on the primary endpoint, a hypothetical strategy will be 
used for death unrelated to COVID-19; a hypothetical strategy will also be used for early 
COVID-19, where the time to COVID-19 will be censored at the onset day of early case. The 
details of intercurrent event description and estimand strategies are presented in Section 11.4.1. 
For the primary efficacy analysis, cases will be counted starting 14 days after the second 
vaccination. Sensitivity analyses with cases counted immediately after the second vaccination, and 
after randomization will also be carried out. 
Analyses of the primary endpoint will be also performed based on the mITT Set using the same 
methods described above. 
For the primary efficacy analysis, cases will be counted starting 14 days after the second dose of 
IP. Sensitivity analyses with cases counted starting immediately after the second dose of IP and 
starting immediately after randomization will also be carried out. 
Subgroup analysis of the primary efficacy endpoint will be performed in selected subgroups, such 
as age groups ≥ 18 and < 65 year and ≥ 65 years to assess consistency of VE as described in 
Section 9.5.5. 
As a supportive analysis, VE will also be estimated by one minus the infection rate ratio, where 
the number of cases (ie, participants with first occurrence of COVID-19) will be used and the CI 
will be computed using the exact method conditional upon the total number of cases. Cumulative 
incidence VE, one minus the ratio of cumulative incidences (mRNA-1273 vs. placebo) of 

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COVID-19, may also be assessed, the cumulative incidence for each arm will be estimated using 
a covariate adjustment method based on Zeng (2004) that makes use of baseline characteristics. 
Additional analysis to evaluate VE against COVID-19 incorporating duration and 
presence/severity of symptoms will also be performed; the details will be provided in the SAP. 
9.5.1.2. 
Efficacy Analysis on Secondary Endpoint 
For each of the below secondary objectives: 
• Vaccine efficacy to prevent severe COVID-19 
• Vaccine efficacy to prevent serologically confirmed SARS-CoV-2 infection or COVID-19 
regardless of symptomatology or severity 
• Vaccine efficacy to prevent COVID-19 using a broad definition of symptoms 
• Vaccine efficacy to prevent death caused by COVID-19 
• Vaccine efficacy to prevent asymptomatic SARS-CoV-2 infection 
For each of the above secondary objectives, the same Cox proportional hazard model described 
above for the primary objective will be applied using the PP Set, with cases counted starting 
14 days after the second dose of IP. Sensitivity analyses with cases counted starting after the 
second dose of IP, 14 days after the first dose of IP, after the first dose of IP, and after 
randomization will also be performed. 
The same model will be applied using the mITT population with cases counted starting 14 days 
after the second dose of IP. 
Vaccine efficacy will be estimated with 1- ratio of incidence rates with the 95% CI using the exact 
method conditional upon the total number of cases. 
Vaccine efficacy to prevent COVID-19 after the first dose of IP 
The same Cox proportional hazard model described above for the primary objective will be applied 
using the PP Set, with cases counted starting 14 days after the first dose of IP. 
Vaccine efficacy to prevent COVID-19 regardless of prior SARS-CoV-2 infection 
The FAS will be used for analysis to evaluate VE to prevent COVID-19 regardless of prior 
SARS-CoV-2 infection. The same methods described above for the primary objective will be 
applied with cases counted starting 14 days after the second dose of IP. Sensitivity analyses with 
cases counted starting after the second dose of IP, 14 days after the first dose of IP, the first dose 
of IP, and randomization will also be performed. 

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Vaccine efficacy will be estimated with 1 – ratio of incidence rates with the 95% CI using the 
exact method conditional upon the total number of cases. 
9.5.1.3. 
Long-term Efficacy Analysis 
Long-term efficacy of the primary vaccination series with mRNA-1273 will be evaluated after the 
primary analysis by including data collected in the Open-Label Observational Phase (Part B). 
Long-term efficacy data will be summarized descriptively by treatment cohort described in 
Table 10 without cohort comparison. The long-term efficacy endpoints are listed in 
Table 11with the same case definitions specified inTable 1. In the primary approach, cases will be 
counted starting 14 days after the second dose of IP for participants in treatment cohorts of 
mRNA-1273 and placebo or starting 14 days after the second dose of mRNA-1273 for participants 
in the Placebo-mRNA-1273 Cohort. Sensitivity analyses with cases starting from the second dose, 
14 days after the first dose, or first dose of IP for participants in the cohorts of mRNA-1273 and 
placebo, or mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort may be provided. 
Incidences of cases assessed by numbers, rates, and 2-sided 95% CI based on the exact method 
adjusting for person-time will be summarized by treatment cohort. The Kaplan-Meier analysis will 
be used to estimate cumulative incidences of time to first cases by treatment cohort. Long-term 
efficacy analysis will be performed using the PP Set and mITT Set. 
Efficacy analyses of unblinded/open-label phase data collected in Part B will be provided, as 
measured by the incidence rate of COVID-19 after the BD of mRNA-1273. The details of analysis 
of long-term efficacy and open-label phase data (Part B and Part C) will be provided in the SAP.  
Table 10: 
Treatment Cohorts for the Long-term Efficacy Analyses 
Treatment Cohort 
Description 
mRNA-1273 
Participants randomized to mRNA-1273 in the Blinded Phase. 
Placebo 
Participants randomized to Placebo in the Blinded Phase and 
did not crossover to mRNA-1273 in the Open-Label 
Observational Phase.  
Placebo-mRNA-1273 
Participants randomized to Placebo in the Blinded Phase and 
crossed over to mRNA-1273 in the Open-Label Observational 
Phase. 
 

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Table 11: 
Long-term Efficacy Endpoints 
Long-term Efficacy Endpoint 
Cases of COVID-19 starting 14 days after the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort. 
Cases of severe COVID-19 starting 14 days after the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Cases of either COVID-19 or SARS-CoV-2 infection starting 14 days after the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Cases with a secondary (less restrictive) definition of COVID-19 starting 14 days after the second 
injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Cases of death due to a cause directly attributed to a complication of COVID-19, starting 14 days after 
the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Cases of COVID-19 starting 14 days after the first injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Regardless of evidence of prior SARS-CoV-2 infection determined by serologic titer against 
SARS-CoV-2 nucleocapsid, cases of COVID-19 starting 14 days after the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Cases of SARS-CoV-2 infection in the absence of symptoms defining COVID-19 starting 14 days after 
the second injection of: 
• 
IP for participants in the mRNA-1273 Cohort and the Placebo Cohort,  
or  
• 
mRNA-1273 for participants in the Placebo-mRNA-1273 Cohort.  
Abbreviations: COVID-19 = coronavirus disease 2019; IP = investigational product; SARS-CoV-2 = severe acute 
respiratory syndrome coronavirus 2. 

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9.5.2. 
Safety Analyses 
All safety analyses will be based on the Safety Set, except summaries of solicited ARs, which will 
be based on the Solicited Safety Set. All safety analyses will be provided by treatment group, and 
by treatment cohort as applicable, unless otherwise specified. Pregnancies and their known 
outcomes will be summarized (Section 8.3.6). 
9.5.2.1. 
Adverse Events 
Safety and reactogenicity will be assessed by clinical review of all relevant parameters. Safety 
analyses will be provided for Parts A, B, and C separately unless specified otherwise.  
The number and percentage of participants with any solicited local AR, with any solicited systemic 
AR, and with any solicited AR during the 7-day follow-up period after each dose will be provided 
only for Part A. A 2-sided 95% exact CI using the Clopper-Pearson method will be also provided 
for the percentage of participants with any solicited AR for each treatment group. Analysis of 
solicited AR will be provided using the Solicited Safety Set for Part A. 
The number and percentage of participants with unsolicited AEs (Part A [all participants] and 
Part C [only those who receive the BD]), SAEs, MAAEs, AESIs (Part C [only those who receive 
the BD]), and AEs leading to discontinuation from IP or withdrawal from the study will be 
summarized. Unsolicited AEs will be presented by MedDRA preferred term and system organ 
class. Analyses of AEs will be provided for Part A and Part B using the Safety Set. For Part C, 
analysis of AEs will be provided in the Part C Safety Set (ie, participants who received booster in 
Part C). 
For all other safety parameters, descriptive summary statistics will be provided, and Table 12 
summarizes the analysis strategy for safety parameters. Further details will be described in the 
SAP. 

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Table 12: 
Analysis Strategy for Safety Parameters in Part A 
Safety Endpoint 
Number and Percentage of 
Participants,  
Number of Events 
95% CI 
Any Solicited AR (Part A; overall and by local, 
systemic) 
X 
X 
Any Unsolicited AE  
X 
 
Any SAE 
X 
 
Any Unsolicited MAAE 
X 
 
Any Unsolicited Treatment-Related AE 
X 
 
Any Treatment-Related SAE 
X 
 
Discontinuation due to AE 
X 
 
Any Grade 3 and above AE  
X 
 
Any Treatment-Related Grade 3 and above AE  
X 
 
Abbreviations: AE = adverse event; AR = adverse reaction; CI =confidence internval; MAAE = medically attended 
adverse event; MedDRA = Medical Dictionary for Regulatory Activities; SAE = serious adverse event. 
Notes: 95% CI using the Clopper-Pearson method, X = results will be provided. Unsolicited AEs will be summarized 
by System Organ Class and Preferred Term coded by MedDRA. Safety parameters will be analyzed in applicable 
study parts and participants as further specified in the statistical analysis plan.  
9.5.2.2. 
Baseline Descriptive Statistics 
Demographic variables and baseline characteristics will be summarized by treatment group, and 
by treatment cohort as applicable, by descriptive statistics (mean, standard deviation for 
continuous variable, and number and percentage for categorical variables). 
9.5.3. 
Immunogenicity Analyses 
The secondary immunogenicity endpoints will be analyzed using the Immunogenicity Subset by 
treatment group, by treatment cohort as applicable, and by baseline SARS-CoV-2 serostatus, 
unless otherwise specified. Details for immunogenicity analyses will be provided in the SAP. 
The SAP will describe the complete set of immunogenicity analyses, including the approach to 
sample individuals into an Immunogenicity Subset for characterizing mRNA-1273 
immunogenicity and assessing immunological correlates of risk and protection. 
9.5.3.1. 
Part A 
Data from quantitative immunogenicity assays will be summarized for each treatment group using 
positive response rates and geometric means with 95% Cis, for each timepoint for which an 
assessment is performed. Data from qualitative (ie, yielding a positive or negative result) assays 
will be summarized by tabulating the frequency of positive responses for each assay by group at 
each timepoint that an assessment is performed. Analyses will focus on the 2 key immunogenicity 

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timepoints and the change in marker response between them: Day 1 before the first dose of IP and 
Day 57 (28 days after the second dose of IP). The SAP will describe the complete set of 
immunogenicity analyses. 
Quantitative levels or geometric mean titer (GMT) of specific bAb with corresponding 95% CI at 
each timepoint and geometric mean fold rise (GMFR) of specific bAb with corresponding 95% CI 
at each postbaseline timepoint over pre-dose baseline at Day 1 will be provided by study arm. 
Descriptive summary statistics including median, minimum, and maximum will also be provided. 
The GMT of specific nAb with corresponding 95% CI at each timepoint and GMFR of specific 
nAb with corresponding 95% CI at each postbaseline timepoint over pre-dose baseline at Day 1 
will be provided by study arm. Descriptive summary statistics including median, minimum, and 
maximum will also be provided. For summarizations of group values, Ab values reported as below 
the LLOQ will be replaced by 0.5 × LLOQ. Values that are reported as greater than the upper limit 
of quantification (ULOQ) without the actual values will be converted to the ULOQ. 
The number and percentage of participants with a fold rise ≥ 2, ≥ 3, and ≥ 4 of serum 
SARS-CoV-2-specific nAb titers and participants with seroresponse from baseline will be 
provided with 2-sided 95% CI using the Clopper-Pearson method at each post-baseline timepoint. 
Seroresponse at a participant level may be defined as a change from below the LLOQ to at least 4 
times the LLOQ, or at least a 4-fold rise in nAb or vaccine antigen-specific bAb in participants 
with pre-existing nAb or bAb of at least the LLOQ at baseline/pre-vaccination. Seroresponse may 
also be defined for each specific assay assessing nAb or bAb. The definition of seroresponse will 
be finalized and documented in the SAP.  
The GMT of specific nAb for each group and the geometric mean ratio (GMR) of mRNA-1273 
versus placebo in Part A with corresponding 2-sided 95% CI will be estimated at each study 
timepoint using an analysis of covariance model with the treatment group and baseline values, if 
applicable, as explanatory variables, the analysis may adjust for the stratification factor (Table 13). 
Table 13: 
Immunogenicity Endpoints and Statistical Methods 
Endpoint 
Statistical Analysis Methods 
Specific bAb and nAb titers/values  
• GMT of each group, GMR (mRNA-1273 vs. placebo) 
• GMT estimated by the ANCOVA model 
Fold rise 
• 
GMFR – descriptive statistics 
• 
Binomial endpoints of fold rise ≥ 2, 3, and 4, and 
seroconversion due to vaccination – the Clopper-Pearson 
method 
Abbreviations: ANCOVA = analysis of covariance; bAb = binding antibody; GMFR = geometric mean fold rise, 
GMR = geometric mean ratio; GMT = geometric mean titer; nAb = neutralizing antibody. 

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9.5.3.2. 
Part C 
In Part C, the immunogenicity analysis of BD vaccine response will be performed using the 
noninferiority tests of the 2 null hypotheses based on the 2 key secondary endpoints, respectively. 
Further considerations for immunogenicity analyses are provided in the SAP. 
Part C Key Secondary Endpoint 1: Ab GMT at BD-Day 29 
Hypothesis: immunogenicity response to mRNA-1273 BD as measured by Ab GMT at BD-Day 29 
in Part C is noninferior compared with Ab GMT at Day 57 (28 days after second dose) in the 
primary series of mRNA-1273. 
The noninferiority of post-booster GMT at BD-Day 29 in Part C as compared to the primary series 
at Day 57 is considered to be demonstrated if the lower bound of the 95% CI of the GMR (ratio of 
GMT at BD-Day 29 vs. GMT at Day 57 [28 days after Dose 2 of the primary series]) is ≥ 0.67 
using a noninferiority margin of 1.5 (1.5-fold immuno-bridging margin for the lower bound of the 
95% CI for GMT ratio/GMR).  
The GMT with 95% CI will be summarized using t-distribution of the log transferred values and 
then back transformed to the original scale. The GMR with 95% CI to compare post-booster GMT 
at BD-Day 29 in Part C with the primary series GMT at Day 57 (28 days after the second dose) 
will be computed based on the t-distribution of mean difference in the log transferred values and 
then back transformed to the original scale. 
Part C Key Secondary Endpoint 2: Ab Seroresponse Rate at BD-Day 29 
Hypothesis: immunogenicity response to mRNA-1273 BD as measured by seroresponse rate 
(SRR) at BD-Day 29 in Part C is noninferior compared with SRR of the primary series at Day 57 
(28 days after second dose of the primary series of mRNA-1273). 
The noninferiority in SRR post-booster at BD-Day 29 in Part C compared with SRR of the primary 
series at Day 57 (28 days after the second dose of the primary series of mRNA-1273) is considered 
to be demonstrated if the lower bound of the 95% CI of the SRR difference (SRR of the booster at 
BD-Day 29 – SRR of the primary series at Day 57) is > –10% (using the noninferiority margin of 
10%). The SRR difference is defined as the seroresponse rate at BD-Day 29 in Part C minus the 
seroresponse rate at Day 57 (28 days after the second dose) following the primary series of 
mRNA-1273. The seroresponse of a booster or the primary series is defined as a titer change from 
baseline (pre-Dose 1 in primary series) below the LLOQ to ≥ 4 × LLOQ, or at least a 4-fold rise if 
baseline is ≥ LLOQ.  
The SRR with 95% CI (using Clopper-Pearson method) will be provided. The SRR difference with 
95% CI to compare post-booster SRR at BD-Day 29 in Part C with the primary series SRR at 

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Day 57 (28 days after the second dose) will be computed. The method for computing 95% CI of 
seroresponse rate difference will be provided in the SAP. 
The primary immunogenicity objective in Part C is met if noninferiority is demonstrated based on 
both key secondary endpoints (both GMT and SRR) . 
9.5.4. 
Exploratory Analyses in Part A 
The endpoint of viral infection kinetics will be assessed by determining the number of days until 
testing of saliva samples becomes negative after COVID-19 is established. 
The endpoint of duration of symptoms will be assessed by determining the total number of days 
that a study participant with COVID-19 remains symptomatic through daily assessments after 
diagnosis. 
Vaccine efficacy to prevent all-cause mortality will be assessed by similar analysis methods as 
used for the primary endpoint analysis, using PP Set, mITT Set, and FAS. All deaths, regardless 
of cause from the time of randomization, will be included. If the number of deaths becomes large 
enough to warrant analysis, the same Cox proportional hazard model described above for the 
primary objective will be applied using the PP Set, the mITT Set, and the FAS. Death, regardless 
of cause, from randomization will be included. 
This endpoint of burden of disease (BOD) is defined based on the post SARS-CoV-2 infection 
follow-up. A BOD score will be used to reflect the severity of symptoms with maximum score at 
COVID-19 death (Table 14).  
Table 14: 
Burden of Disease Score 
Patient State 
BOD Score 
Uninfected/Asymptomatic infection  
0 
Symptomatic without hospitalization 
1 
Hospitalization 
2 
Death 
3 
Abbreviation: BOD = burden of disease. 
9.5.5. 
Subgroup Analyses 
To determine whether the VE is consistent across various subgroups, the VE and its 95% CI may 
be estimated using the similar model within each category of the following classification variables. 
• Age groups: ≥ 18, < 65, and ≥ 65 
• Age and health risk for severe disease: ≥ 18 and < 65 and not at risk; ≥ 18 and < 65 and at 
risk, and ≥ 65 

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• Sex (female, male) 
• Race  
• At risk for severe COVID-19 illness (Section 6.2.1.1) 
Subgroup analysis for the long-term efficacy may be performed descriptively by treatment cohort 
within above categories. 
9.6. 
Interim Analyses 
In Part A, there are 2 planned IAs at 35% and 70% of total target cases across the 2 treatment 
groups. The primary objective of the IAs is for early detection of reliable evidence that VE is above 
30%. The Lan-DeMets O’Brien-Fleming approximation spending function is used for calculating 
efficacy bounds and to preserve the (1-sided) 0.025 false positive error rate over the IAs and the 
primary analysis (when the target number of cases have been observed), relative to the hypothesis: 
H0efficacy: HR ≥ 0.7 (equivalently, proportional hazards VE ≤ 0.3). 
There is no intention to stop the study early if the efficacy has been demonstrated at any of the 
IAs. If efficacy is demonstrated at an IA, the subsequent IA or primary analysis will be considered 
supportive in nature. The DSMB will review the IA results and make recommendations to the 
Sponsor in terms of study results reporting and unblinding based on the boundaries of early 
efficacy as described in this section, safety data, and data external to this study. In addition to 
possible early efficacy at IAs, the DSMB will monitor for non-efficacy and vaccine harm; the 
guiding principles (non-binding) is provided in Section 8.4.2, and the details will be provided in 
the SAP. 
Table 15 summarizes the timing, number of cases and decision guidance at each IA and primary 
analysis. 
The first IA will occur when approximately 35% of the total cases have been observed (across 
both treatment groups). The study will be considered positive at the first IA if the p-value for 
rejecting HR ≥ 0.7 is less than 0.0002 based on the Lan-DeMets O’Brien-Fleming approximation 
spending function. This corresponds to an observed HR of approximately 0.259, or an observed 
VE approximately 0.741. 
The second IA will occur when approximately 70% of the total cases have been observed. The 
study will be considered positive (VE has been demonstrate) if the p-value for rejecting HR ≥ 0.7 
is less than 0.0073 based on the Lan-DeMets O’Brien-Fleming approximation spending function. 
This corresponds to an observed HR of approximately 0.435, or an observed VE of approximately 
0.565. 

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The primary analysis will be performed when approximately 151 cases have been observed in the 
study. The study will be considered positive at the primary analysis if the 1-sided p-value for 
rejecting HR ≥ 0.7 is less than 0.0227. This corresponds to an observed HR of approximately 0.505 
or observed VE of approximately 0.495. 
Table 15: 
Interim Boundaries Using O’Brien-Fleming Spending Function, Calculation 
Based on the PP Set for the Primary Efficacy Endpoint 
Information Fraction 
(% of total #cases) 
Number 
of Cases 
Nominal 
Alpha 
Efficacy Boundary 
Rejecting H0: VE ≤ 30% 
Cum Prob 
(crossing efficacy 
boundary if the 
true VE = 60%) 
IA1 35% 
53 
0.0002 
VE ≥ 0.741 
(HR ≤ 0.259) 
4.6% 
IA2 70% 
106 
0.0073 
VE ≥ 0.565 
(HR ≤ 0.435) 
61.5% 
Primary analysis 100% 
151 
0.0227 
VE ≥ 0.495 
(HR ≤ 0.505) 
90.0% 
Abbreviations: HR = hazard ratio; IA: = interim analysis; PP = per-protocol; VE = vaccine efficacy. 

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Trial Populations – Eligibility Criteria, Enrollment Practices, and Trial Designs. November 2020b. 
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Wang L, Shi W, Chappell JD, Joyce MG, Zhang Y, Kanekiyo M, et al. Importance of neutralizing 
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11. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 

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11.1. 
APPENDIX 1: Schedules of Events 
If a participant cannot attend a study site visit (scheduled or unscheduled, with the exception of 
Screening, Day 1, Day 29, PDV, OL-D1, OL-D29, and BD-1), a home visit is acceptable if 
performed by appropriately delegated study site staff or a home healthcare service provided by the 
Sponsor. If neither a participant visit to the study site nor a home visit to the participant is possible 
(with the exception of Screening, Day 1, Day 29, PDV, OL-D1, OL-D29, and BD-1), a safety 
phone call should be performed that includes the assessments scheduled for the biweekly safety 
phone calls (Table 16).  
The Supplemental SoEs (Table 21 and Table 23) and the Modified Supplemental SoE (Table 22) 
are intended to occur in addition to the original SoEs, as applicable (Table 16, 
Table 17Table 18Table 19), and therefore there is a possibility for study visits to overlap. If visits 
overlap according to respective visit windows, a single visit may be completed with any duplicated 
study procedures each completed once (refer to Table 4 footnotes for more detailed instructions 
and exceptions).  
 
 

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Table 16: 
Schedule of Events (Vaccination Phase, Day 1 – Day 57) 
Visit Number 
0 
1 
 
 
 
2 
 
 
 
3 
Type of Visit C 
C 
SC 
SC 
SC 
C 
SC 
SC 
SC 
C 
Month/Weekly Timepoint 
 
M0 
 
 
 
M1 
 
 
 
M2 
Study Visit Day  
D01 (Screening) 
D1 (Baseline) 
7 days after D1 
D8 
14 days after D1 
D15 
21 days after D1 
D22 
D29 
7 days after D29 
D36 
14 days after D29 
D43 
21 days after D29 
D50 
D57 
Window Allowance (Days) 
-28 
 
+3 
+3 
+3 
-3/+7 
+3 
+3 
+3 
-3/+7 
Days Since Most Recent Vaccination 
- 
0 
7 
14 
21 
28/0 
7 
14 
21 
28 
ICF, demographics, concomitant medications, medical history 
X 
 
 
 
 
 
 
 
 
 
Confirm participant meets inclusion and exclusion criteria 
X 
X 
 
 
 
 
 
 
 
 
Physical examination2 
X 
X 
 
 
 
X 
 
 
 
X 
Pregnancy testing3 
X 
X 
 
 
 
X 
 
 
 
 
Randomization 
 
X 
 
 
 
 
 
 
 
 
Dosing 
Study injection (including 30-minute post-dosing observation 
period) 
 
X 
 
 
 
X 
 
 
 
 
Efficacy Assessment 
Surveillance for COVID-19/Unscheduled Visit4 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Nasopharyngeal swab5 
 
X 
 
 
 
X 
 
 
 
 
Immunogenicity Assessment 
Blood for immunologic analysis5 
 
X 
 
 
 
X 
 
 
 
X 

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Visit Number 
0 
1 
 
 
 
2 
 
 
 
3 
Type of Visit C 
C 
SC 
SC 
SC 
C 
SC 
SC 
SC 
C 
Month/Weekly Timepoint 
 
M0 
 
 
 
M1 
 
 
 
M2 
Study Visit Day  
D01 (Screening) 
D1 (Baseline) 
7 days after D1 
D8 
14 days after D1 
D15 
21 days after D1 
D22 
D29 
7 days after D29 
D36 
14 days after D29 
D43 
21 days after D29 
D50 
D57 
Window Allowance (Days) 
-28 
 
+3 
+3 
+3 
-3/+7 
+3 
+3 
+3 
-3/+7 
Days Since Most Recent Vaccination 
- 
0 
7 
14 
21 
28/0 
7 
14 
21 
28 
Safety Assessments 
eDiary activation for recording solicited adverse reactions 
(7 days)6 
 
X 
 
 
 
X 
 
 
 
 
Review of eDiary 
 
 
X 
 
 
 
X 
 
 
 
Follow-up safety7 
 
 
X 
X 
X 
 
X 
X 
X 
 
Recording of unsolicited AEs  
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of MAAEs, AE leading to withdrawal, and 
concomitant medications relevant to or for the treatment of 
the MAAE8 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of SAEs and concomitant medications relevant to 
or for the treatment of the SAE8 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and non-study 
vaccinations8 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Abbreviations: AE = adverse event; AR = adverse reaction; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; eDiary = electronic diary; 
FDA = Food and Drug Administration; ICF = informed consent form; M = month; MAAE = medically attended AE; NP = nasopharyngeal; RT-PCR = reverse 
transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety (phone) call. 

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Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. All scheduled study visits should be completed within the respective visit windows. 
If the participant is not able to come on-site for a study site visit as a result of the COVID-19 pandemic (self-quarantine or disruption of study site activities 
following business continuity plans and/or local government mandates for “stay at home” or “shelter in place”), a safety call to the participant should be made in 
place of the study site visit. The safety call should encompass all scheduled visit assessments that can be completed remotely, such as assessment for AEs and 
concomitant medications (eg, as defined in scheduled biweekly safety phone calls). Home visits will be permitted for all non-dosing visits except for Screening 
if a participant cannot come to the study site as a result of the COVID-19 pandemic. 
1. 
Day 0 and Day 1 may be combined the same day. Additionally, the Day 0 visit may be performed over multiple visits if within the 28-day screening window. 
2. 
Physical examination: a full physical examination, including vital signs, height, and weight, will be performed at Screening and Day 1. Body mass index 
will be calculated at the Screening Visit (Day 0) only. Symptom-directed physical examinations will be performed on Day 29 and Day 57. On each dosing 
day before injection, the arm receiving the injection should be examined and the associated lymph nodes should be evaluated. Any clinically significant 
finding identified during a study visit should be reported as an MAAE. Vital signs are to be collected pre- and post-dosing on days of injection (Day 1 and 
Day 29). When applicable, vital sign measurements should be performed before blood collection. Participants who are febrile (body temperature 
≥ 38.0°C/100.4°F) before dosing on Day 1 or Day 29 must be rescheduled within the relevant window period to receive the injection. Afebrile participants 
with minor illnesses can be enrolled at the discretion of the investigator. 
3. 
Pregnancy test at Screening and Day 1 and before the second vaccination will be a point-of-care urine test. At the discretion of the investigator a pregnancy 
test either via blood or point-of-care urine test can be performed. Follicle-stimulating hormone level may be measured to confirm menopausal status at the 
discretion of the investigator. 
4. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to include 
an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to collect the NP 
swab sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study site by a 
Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. An additional 
NP swab sample will be collected to test for the presence of other respiratory pathogens. Additionally, clinical information will be carefully collected to 
evaluate the severity of the clinical case. It is important to note that some of the symptoms of COVID-19 overlap with solicited systemic ARs that are 
expected after vaccination with mRNA-1273 (eg, myalgia, headache, fever, and chills). During the first 7 days after vaccination, when these solicited ARs 
are common, investigators should use their clinical judgement to decide if an NP swab should be collected. The collection of an NP swab prior to the Day 1 
and Day 29 vaccination can help ensure that cases of COVID-19 are not overlooked. Any study participant reporting respiratory symptoms during the 7-day 
period after vaccination should be evaluated for COVID-19. 
5. 
Sample must be collected prior to dosing on days of injection (Day 1 and Day 29). 
6. 
The participant will record entries in the eDiary approximately 30 minutes after dosing while at the study site, with instruction provided by study staff. Study 
participants will continue to record in the eDiary each day after they leave the study site, preferably in the evening, on the day of dosing and for 6 days 
following. Any solicited AR that is ongoing beyond Day 7 will be reported until resolution. Adverse reactions recorded in eDiaries beyond Day 7 should be 
reviewed either via phone call or at the following study visit. Participants will be given thermometers to record their temperatures and rulers to measure any 
injection site reactions. 
7. 
Trained study personnel will call all participants to collect information relating to any unsolicited AEs through Day 57 (including any signs and symptoms 
of COVID-19), MAAEs, AEs leading to withdrawal, SAEs, information on concomitant medications associated with those events, and any non-study 
vaccinations. 
8. 
All concomitant medications and non-study vaccinations will be recorded through 28 days after each injection; all concomitant medications relevant to or 
for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 

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Table 17: 
Schedule of Events (Surveillance Phase, Day 64 – Day 394) 
Visit Number 
 
 
 
 
 
4 
 
 
 
 
 
5 
Type of Visit 
eDiary 
SC 
SC 
SC 
SC 
C 
SC 
SC 
SC 
SC 
SC 
C 
Month (M)/Weekly (W) Timepoint 
W 
M3 
M4 
M5 M6 
M7 
M8 
M9 M10 M11 M12 
M13 
Study Visit Day  
D641 
D851 
D119 1 
90 days after 
D29 
D1491 
D1791 
D2091 
180 days after 
D29
D2391 
D2691 
D2991 
D3291 
D3591 
D3941 
365 days after 
D29  
 
Window Allowance (Days) 
±2 
±3 
±3 
±3 
±3 
±14 
±3 
±3 
±3 
±3 
±3 
±14 
Days Since Most Recent Vaccination 
- 
56 
90 
120 150 
180 
210 
240 
270 300 330 
365 
Physical examination2 
 
 
 
 
 
X 
 
 
 
 
 
X 
Efficacy Assessments 
eDiary activation for surveillance for 
COVID-19/Unscheduled Visit 
X 
 
 
 
 
 
 
 
 
 
 
 
eDiary Weekly prompts for surveillance for 
COVID-19 
-----------------Weekly eDiary prompts (Day 64 through Day 759)------------------ 
Surveillance for COVID-19/Unscheduled Visit3 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Immunogenicity Assessment 
Blood for immunologic analysis 
 
 
 
 
 
X 
 
 
 
 
 
X 
Safety Assessments 
eDiary activation for safety follow-up 
X4 
 
 
 
 
 
 
 
 
 
 
 
eDiary Weekly prompts for safety follow-up 
--------------Weekly eDiary prompts (Day 64 through Day 759)--------------------- 

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Visit Number 
 
 
 
 
 
4 
 
 
 
 
 
5 
Type of Visit 
eDiary 
SC 
SC 
SC 
SC 
C 
SC 
SC 
SC 
SC 
SC 
C 
Month (M)/Weekly (W) Timepoint 
W 
M3 
M4 
M5 M6 
M7 
M8 
M9 M10 M11 M12 
M13 
Study Visit Day  
D641 
D851 
D119 1 
90 days after 
D29 
D1491 
D1791 
D2091 
180 days after 
D29
D2391 
D2691 
D2991 
D3291 
D3591 
D3941 
365 days after 
D29  
 
Window Allowance (Days) 
±2 
±3 
±3 
±3 
±3 
±14 
±3 
±3 
±3 
±3 
±3 
±14 
Days Since Most Recent Vaccination 
- 
56 
90 
120 150 
180 
210 
240 
270 300 330 
365 
Follow-up safety5 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of MAAEs, AESIs (Part C), AE leading to 
withdrawal and concomitant medications relevant to or 
for the treatment of the MAAE6 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of SAEs and concomitant medications 
relevant to or for the treatment of the SAE6 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and non-study 
vaccinations6,7 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; 
eDiary = electronic diary; ePRO = electronic patient-reported outcome; FDA = Food and Drug Administration; IRB = institutional review board; M = month; 
MAAE = medically attended AE; NP= nasopharyngeal swab; RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; 
SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety (phone) call; W = week. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. 
1. 
All scheduled study visits should be completed within the respective visit windows. If the participant is not able to come on-site for a study site visit as a 
result of the COVID-19 pandemic (self-quarantine or disruption of study site activities following business continuity plans and/or local government mandates 
for “stay at home” or “shelter in place”), a safety phone call to the participant should be made in place of the study site visit. The safety call should encompass 
all scheduled visit assessments that can be completed remotely, such as assessment for AEs and concomitant medications (eg, as defined in scheduled safety 
phone calls). Home visits will be permitted for all non-dosing visits except for Screening if a participant cannot come to the study site as a result of the 

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COVID-19 pandemic. Home visits must be permitted by the site IRB and the participant via informed consent and have prior approval from the Sponsor (or 
its designee). 
2. 
Symptom-directed physical examinations may be performed at the discretion of the investigator. 
3. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to include 
an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to collect the NP 
swab sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study site by a 
Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. An additional 
NP swab sample will be collected to test for the presence of other respiratory pathogens. In addition, the study site may collect an additional (local/non-central) 
respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as determined by local standards of care. 
Additionally, clinical information will be carefully collected to evaluate the severity of the clinical case. 
4. 
The eDiary Safety Follow-up prompts will be triggering off of Day 61 to take into consideration the (-3 day) window allowance at Day 29. This first Safety 
Follow-Up prompt at Day 61 will follow the same 7-day surveillance per protocol. 
5. 
Trained study personnel will call all participants to collect information relating to any sign/symptoms of COVID-19, MAAEs, AESIs, AEs leading to 
withdrawal, SAEs, information on concomitant medications associated with those events, and any non-study vaccinations. 
6. 
All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 
7. 
One additional ePRO prompt will be sent to participants specifically to solicit the collection of information regarding participant’s history of facial injections 
or dermal fillers, for cosmetic or medical indications such as migraine headaches. 
 

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Table 18: 
Schedule of Events (Surveillance Phase, Day 401 – Day 759) 
Visit Number 
 
 
 
 
 
6 
Type of Visit 
SC 
SC 
SC 
SC 
SC 
C 
Month (M)/Weekly (W) Timepoint 
M15 
M17 
M19 
M21 
M23 
M25 
Study Visit Day  
D4541 
D5141 
D5741 
D6341 
D6941 
D7591 
365 days after 
 Year 1 
Window Allowance (Days) 
±7 
±7 
±7 
±7 
±7 
-14/+28 
Days Since Most Recent Vaccination 
 
 
 
 
 
730 
Physical examination2 
 
 
 
 
 
X 
eDiary weekly prompts for surveillance for COVID-19 
----Weekly eDiary prompts (Day 401 through Day 759)------------ 
Surveillance for COVID-19/Unscheduled Visit3 
X 
X 
X 
X 
X 
X 
Blood for immunologic analysis 
 
 
 
 
 
X 
eDiary weekly prompts for safety follow-up 
-----Weekly eDiary prompts (Day 401 through Day 759)----------- 
Follow-up safety4 
X 
X 
X 
X 
X 
X 
Recording of MAAEs, AESIs (Part C), AE leading to withdrawal and 
concomitant medications relevant to or for the treatment of the 
MAAE5 
X 
X 
X 
X 
X 
X 
Recording of SAEs and concomitant medications relevant to or for the 
treatment of the SAE5 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and non-study vaccinations5 
X 
X 
X 
X 
X 
X 

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Abbreviations: AE = adverse event; AESI = adverse event of special interest; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; 
eDiary = electronic diary; FDA = Food and Drug Administration; IRB = institutional review board; M = month; MAAE = medically attended AE; 
NP= nasopharyngeal swab; RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory 
syndrome coronavirus 2; SC = safety (phone) call W = week. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. 
1. 
All scheduled study visits should be completed within the respective visit windows. If the participant is not able to come on-site for a study site visit as a 
result of the COVID-19 pandemic (self-quarantine or disruption of study site activities following business continuity plans and/or local government mandates 
for “stay at home” or “shelter in place”), a safety phone call to the participant should be made in place of the study site visit. The safety phone call should 
encompass all scheduled visit assessments that can be completed remotely, such as assessment for AEs and concomitant medications (eg, as defined in 
scheduled safety phone calls). Home visits will be permitted for all non-dosing visits except for Screening if a participant cannot come to the study site as a 
result of the COVID-19 pandemic. Home visits must be permitted by the site IRB and the participant via informed consent and have prior approval from the 
Sponsor (or its designee). 
2. 
Symptom-directed physical examinations may be performed at the discretion of the investigator. 
3. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to include 
an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to collect the NP 
swab sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study site by a 
Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. An additional 
NP swab sample will be collected to test for the presence of other respiratory pathogens. In addition, the study site may collect an additional (local/non-central) 
respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as determined by local standards of care. 
Additionally, clinical information will be carefully collected to evaluate the severity of the clinical case. 
4. 
Trained study personnel will call all participants to collect information relating to any MAAEs, AESIs, AEs leading to withdrawal, SAEs, information on 
concomitant medications associated with those events, and any non-study vaccinations. 
5. 
All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 

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Table 19: 
Schedule of Events (Convalescent Period, Starting With the Illness Visit) 
Unscheduled Visit 
1 
 
 
 
 
 
 
 
2 
Type of Visit 
C/H 
 
 
 
 
 
 
 
C/H 
Daily Timepoint 
D1 
D2- D6 
D7 D8-D13 D14 D15-D20 
D21 
D22-D27 D28 
Window Allowance (Days) 
- 
±1 
±1 
±1 
±1 
±1 
±1 
±1 
+7 
Safety Assessments 
Symptom-directed physical examination1 
X 
 
 
 
 
 
 
 
X 
Follow-up safety2 
X 
 
 
 
 
 
 
 
X 
Recording of MAAEs, AESIs (Part C), AE leading to withdrawal 
and concomitant medications relevant to or for the treatment of 
the MAAE3 
X 
 
 
 
 
 
 
 
X 
Recording of SAEs and concomitant medications relevant to or 
for the treatment of the SAE3 
X 
 
 
 
 
 
 
 
X 
Recording of concomitant medications and non-study 
vaccinations3 
X 
 
 
 
 
 
 
 
X 
Efficacy Assessments 
Daily telemedicine visit4 
 
--------------------------------------Daily-------------------------- 
Respiratory illness sample5 
X 
 
 
 
 
 
 
 
 
Blood sample for immunologic assessment of SARS-CoV-2 
infection6 
X 
 
 
 
 
 
 
 
X 
Saliva sample 
 
D37, D57 D77 
D97 
D147 
 
D217 
 
X8 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; C = clinic visit; CLIA = Clinical Laboratory Improvement Amendments; 
COVID-19 = coronavirus disease 2019; D = day; FDA = Food and Drug Administration; H = home visit; MAAE = medically attended AE; NP= nasopharyngeal 
swab; RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. 

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1. 
Physical examination: a symptom-directed physical examination, including vital signs will be performed at the initial visit to confirm the diagnosis 
(denoted as D1 in this table) and at the Convalescent Visit (28 days after diagnosis [D28 in this table]). 
2. 
Trained study personnel will call all participants to collect information relating to any AEs, MAAEs, AEs leading to withdrawal, SAEs, information on 
concomitant medications associated with those events, and any non-study vaccinations. All safety events will be followed until resolution. 
3. 
All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 
4. 
Participants will have daily telemedicine visits (via video or phone) for 14 days (from the point of the Illness Visit or initial COVID-19 contact) or until 
symptoms resolve, whichever is later, and which may include symptoms persisting longer than the 28-day Convalescent Period, with the exception of 
mild loss of sense of taste/smell). If a participant is completely asymptomatic for 72 hours prior to Day 14, including normal oxygen saturation and 
temperature, then telemedicine calls can be reduced to weekly; however, the participant should still report the daily symptoms at that contact. The 
participant should also report their oxygen saturation and temperature measured on the day of the contact, but these need not be recorded daily during this 
reduced frequency monitoring period. If a participant reports a change or recurrence of symptoms, daily telemedicine visits should be resumed to the daily 
schedule. For these participants, a final telemedicine visit will occur on Day 14 to determine before symptom monitoring can be discontinued.  If symptoms 
persist after Day 60, then telemedicine calls can be reduced to weekly; however, the participant should still report the daily symptoms at that contact. 
Telemedicine visits may be performed by medically qualified staff appropriately delegated by the investigator. During the telemedicine visit (preferably 
done in the evening) the participant will be asked to verbally report the severity of each symptom and their highest body temperature and lowest oxygen 
saturation for that day, and the investigator will determine if medical attention is required due to worsening of COVID-19. The participant will also be 
reminded to collect a saliva sample and return it to the study site, on the appropriate days. Please note, the negative (-1 day) window allowance does not 
apply to these daily telemedicine visits and if the +1 day window is used, the site should still collect symptoms from the participant for the previous day.  
5. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site or medically qualified staff from 
the site will conduct a home visit as soon as possible to collect an NP swab sample (for RT-PCR) and collect a blood sample for immunologic assessment 
of SARS-CoV-2 infection and evaluate for COVID-19. An additional NP swab sample will also be tested for the presence of other respiratory pathogens. 
In addition, the study site may collect an additional (local/non-central) respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical 
care for the study participant as determined by local standards of care. Additionally, clinical information will be carefully collected to evaluate the severity 
of the clinical case. If the RT-PCR test from the NP swab sample from the Illness Visit is negative for SARS-CoV-2, the participant will exit the 
Convalescent Period and resume the study schedule (Table 16, Table 17, and Table 18). 
6. 
This can be a home visit if necessary. 
7. 
Participants will collect their own saliva sample using the saliva collection tubes provided on 3, 5, 7, 9, 14, and 21 days after the initial Illness Visit, and 
return them to the study site according to Sponsor instructions. Participants who are pending a central laboratory RT-PCR may exit from the Convalescent 
Period based on a negative RT-PCR result from a CLIA-certified or CLIA-certified waiver local laboratory at the investigator’s discretion. 
8. 
At this visit, a saliva sample will be collected. 

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Table 20: 
Part B: Participant Decision Visit 
 
All Participants 
Sign revised informed consent form  
X 
Confirm participant’s request to be unblinded 
or not to be unblinded1 
X 
Nasopharyngeal swab 
X 
Blood for immunologic analysis 
X 
Counselling the importance of public health 
measures2 
X 
Participant Status after PDV 
Blinded 
Cohort 
Open-label Cohort 
Previously 
Receiving 
mRNA-1273 
Remaining on 
Placebo 
Placebo Requesting 
mRNA-1273 
mRNA-1273 who 
Received 1 Dose 
ONLY 
Continue with original schedules of events, as 
applicable (Table 16, Table 17, Table 18, and 
Table 19) 
X 
X 
X 
X 
X 
Supplemental Schedule of Events: 
Open-Label Days 1-57 (Table 21)c 
-- 
-- 
-- 
X 
-- 
Modified Supplemental Schedule of Events: 
Open-Label Days 1-57 (Table 22)3 
-- 
-- 
-- 
-- 
X 
Abbreviation: PDV = participant decision visit.  
1. 
At the point when the mRNA-1273 vaccine is no longer available for study use, any participant who schedules a PDV after this timepoint will be unblinded 
(with no option to stay blinded), but will not be offered mRNA-1273 study vaccine. 
2. 
All participants are counselled about the importance of continuing other public health measures to limit the spread of disease including physical-social 
distancing, wearing a mask, and hand-washing. 
3. 
The Supplemental and the Modified Supplemental Schedule of Events are intended to occur in addition to the original schedules of events, as applicable 
(Table 16, Table 17, Table 18, and Table 19) and therefore there is a possibility for study visits to overlap. If visits overlap according to respective visit 
windows, a single visit may be done with the combined study procedures completed once. 

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Table 21: 
Supplemental Schedule of Events: Open-Label Observational Phase - Placebo Participants who Request to 
Receive mRNA-1273 
NOTE: Supplemental Schedule of Events: Open-Label Observational Phase is to be used ONLY for participants who received placebo 
during the Blinded Phase of this study (Part A), and request to receive mRNA-1273. These participants will comply with this 
Supplemental SoE (Table 21) in addition to the original SoEs as applicable (Table 16, Table 17, Table 18, and Table 19). As this 
Supplemental SoE is intended to occur in addition to the original SoE, there is a possibility for study visits to overlap. If visits overlap 
according to respective visit windows, a single visit may be done with the combined study procedures completed once. 
Visit Number 
0 
OL-1 
 
OL-2 
 
OL-3 
Type of Visit 
C 
C 
SC 
C 
SC 
C 
Study Visit Day  
PDV1 and  
OL-D11 
7 days after OL-D1 
(OL-D8) 
OL-D29 
7 days after OL-D29 
(OL-D36) 
OL-D57 
Window Allowance (Days) 
- 
+3 
-3/+14 
+3 
-3/+14 
Days Since Most Recent Vaccination 
0 
7 
28/0 
7 
28 
Confirm signing of ICF, concomitant medications, medical history 
X 
 
 
 
 
Confirm participant meets inclusion and exclusion criteria  
X 
 
 
 
 
Physical examination2  
X 
 
X 
 
X 
Pregnancy testing3  
X 
 
X 
 
 
Immunogenicity Assessment 
 
 
 
 
 
Blood for immunologic analysis5 
X 
 
 
 
X 
Dosing 
Study injection (including 30-minute post-dosing observation period6) 
X 
 
X 
 
 
Efficacy Assessment 
Surveillance for COVID-19/Unscheduled Visit4 
X 
X 
X 
X 
X 
Nasopharyngeal swab5 
X 
 
 
 
 

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NOTE: Supplemental Schedule of Events: Open-Label Observational Phase is to be used ONLY for participants who received placebo 
during the Blinded Phase of this study (Part A), and request to receive mRNA-1273. These participants will comply with this 
Supplemental SoE (Table 21) in addition to the original SoEs as applicable (Table 16, Table 17, Table 18, and Table 19). As this 
Supplemental SoE is intended to occur in addition to the original SoE, there is a possibility for study visits to overlap. If visits overlap 
according to respective visit windows, a single visit may be done with the combined study procedures completed once. 
Visit Number 
0 
OL-1 
 
OL-2 
 
OL-3 
Type of Visit 
C 
C 
SC 
C 
SC 
C 
Study Visit Day  
PDV1 and  
OL-D11 
7 days after OL-D1 
(OL-D8) 
OL-D29 
7 days after OL-D29 
(OL-D36) 
OL-D57 
Window Allowance (Days) 
- 
+3 
-3/+14 
+3 
-3/+14 
Days Since Most Recent Vaccination 
0 
7 
28/0 
7 
28 
Safety Assessments 
Follow-up safety7 
 
X 
 
X 
 
Recording of MAAEs, AE leading to withdrawal, and concomitant 
medications relevant to or for the treatment of the MAAE8  
X 
X 
X 
X 
X 
Recording of SAEs and concomitant medications relevant to or for the 
treatment of the SAE8  
X 
X 
X 
X 
X 
Recording of concomitant medications and non-study vaccinations8 
X 
X 
X 
X 
X 
Abbreviations: AE = adverse event; AR = adverse reaction; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; FDA = Food and Drug 
Administration; ICF = informed consent form; MAAE = medically attended AE; NP = nasopharyngeal; OL = open-label; PDV = participant decision visit; 
RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; 
SC = safety (phone) call; SoE = Schedule of Events. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. All scheduled study visits should be completed within the respective visit windows. 
If the participant is not able to come on-site for a study site visit as a result of the COVID-19 pandemic (self-quarantine or disruption of study site activities 
following business continuity plans and/or local government mandates for “stay at home” or “shelter in place”), a safety call to the participant should be made in 
place of the study site visit. The safety call should encompass all scheduled visit assessments that can be completed remotely, such as assessment for AEs and 

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concomitant medications (eg, as defined in scheduled biweekly safety phone calls). Home visits will be permitted for all non-dosing visits except for Screening 
if a participant cannot come to the study site as a result of the COVID-19 pandemic. 
4. 
The Day 0 and OL-D1 visit may be performed on 2 separate visits. 
5. 
Symptom-directed physical examination will be performed at the PDV and on OL-D29. On each dosing day before injection, the arm receiving the 
injection should be examined and the associated lymph nodes should be evaluated. Any clinically significant finding identified during a study visit should 
be reported as an MAAE. Vital signs are to be collected pre- and post-dosing on days of injection (OL-D1 and OL-D29). Participants who are febrile 
(body temperature ≥ 38.0°C/100.4°F) before dosing (OL-D1 and OL-D29) must be rescheduled within the relevant window period to receive the injection. 
Afebrile participants with minor illnesses can be enrolled at the discretion of the investigator. 
6. 
Pregnancy test at the PDV and OL-D29 will be a point-of-care urine test. At the discretion of the investigator, a pregnancy test either via blood or point-of-
care urine test can be performed. Follicle-stimulating hormone level may be measured to confirm menopausal status at the discretion of the investigator. 
7. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to 
include an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to collect 
the NP sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study site by 
a Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. An 
additional NP swab sample will be collected to test for the presence of other respiratory pathogens. In addition, the study site may collect an additional 
(local/non-central) respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as determined by 
local standards of care. Additionally, clinical information will be carefully collected to evaluate the severity of the clinical case. It is important to note that 
some of the symptoms of COVID-19 overlap with solicited systemic ARs that are expected after vaccination with mRNA-1273 (eg, myalgia, headache, 
fever, and chills). During the first 7 days after vaccination, when these solicited ARs are common, investigators should use their clinical judgement to 
decide if an NP swab should be collected. The collection of an NP swab prior to the PDV can help ensure that cases of COVID-19 are not overlooked. 
Any study participant reporting respiratory symptoms during the 7-day period after vaccination should be evaluated for COVID-19. 
8. 
Sample must be collected prior to unblinding and injection at the PDV. 
9. 
Post-dosing, participants will have a 30-minute observation period.  
10. Trained study personnel will call all participants to collect information relating to any MAAEs (including any signs and symptoms of COVID-19), AESIs, 
AEs leading to withdrawal, SAEs, information on concomitant medications associated with those events, and any non-study vaccinations. 
11. All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 

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Table 22: 
Modified Supplemental Schedule of Events: Open-Label Observational Phase – mRNA-1273 Participants Who 
ONLY Received 1 Dose of mRNA-1273 
NOTE: Modified Supplemental Schedule of Events: Open-Label Observational Phase is to be used ONLY for participants who ONLY 
received 1 dose of mRNA-1273 during the Blinded Phase of this study (Part A) and consented to receive mRNA-1273 (see Section 4.1.2 
for details). These participants will comply with this SoE (Table 22) in addition to the original SoEs as applicable (Table 16, Table 17, 
Table 18, and Table 19). As this Modified Supplemental SoE is intended to occur in addition to the original SoE, there is a possibility for 
study visits to overlap. If visits overlap according to respective visit windows, a single visit may be done with the combined study 
procedures completed once. 
Visit Number 
0 
OL-1 
 
OL-2 
Type of Visit 
C 
C 
SC 
C 
Study Visit Day  
PDV1 and OL-D11 
7 days after  
OL-D1 
OL-D8 
OL-D29 
Window Allowance (Days) 
- 
+3 
-3/+14 
Days Since Most Recent Vaccination 
0 
7 
28 
Confirm signing of ICF, concomitant medications, medical history 
X 
 
 
Confirm participant meets inclusion and exclusion criteria  
X 
 
 
Physical examination2  
X 
 
X 
Pregnancy testing3  
X 
 
 
Immunogenicity Assessment 
 
 
 
Blood for immunologic analysis4 
X 
 
X 
Dosing 
Study injection (including 30-minute post-dosing observation period5) 
X 
 
 

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NOTE: Modified Supplemental Schedule of Events: Open-Label Observational Phase is to be used ONLY for participants who ONLY 
received 1 dose of mRNA-1273 during the Blinded Phase of this study (Part A) and consented to receive mRNA-1273 (see Section 4.1.2 
for details). These participants will comply with this SoE (Table 22) in addition to the original SoEs as applicable (Table 16, Table 17, 
Table 18, and Table 19). As this Modified Supplemental SoE is intended to occur in addition to the original SoE, there is a possibility for 
study visits to overlap. If visits overlap according to respective visit windows, a single visit may be done with the combined study 
procedures completed once. 
Visit Number 
0 
OL-1 
 
OL-2 
Type of Visit 
C 
C 
SC 
C 
Study Visit Day  
PDV1 and OL-D11 
7 days after  
OL-D1 
OL-D8 
OL-D29 
Window Allowance (Days) 
- 
+3 
-3/+14 
Days Since Most Recent Vaccination 
0 
7 
28 
Efficacy Assessment 
Surveillance for COVID-19/Unscheduled Visit6 
X 
X 
X 
Nasopharyngeal swab5 
X 
 
 
Safety Assessments 
 
Follow-up safety7 
 
X 
 
Recording of MAAEs, AE leading to withdrawal, and concomitant medications relevant 
to or for the treatment of the MAAE8  
X 
X 
X 
Recording of SAEs and concomitant medications relevant to or for the treatment of the 
SAE8  
X 
X 
X 
Recording of concomitant medications and non-study vaccinations8 
X 
X 
X 

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Abbreviations: AE = adverse event; AR = adverse reaction; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; FDA = Food and Drug 
Administration; ICF = informed consent form; MAAE = medically attended AE; NP = nasopharyngeal; OL = open-label; PDV = participant decision visit; 
RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; 
SC = safety (phone) call; SoE = Schedule of Events. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. All scheduled study visits should be completed within the respective visit windows. 
If the participant is not able to come on-site for a study site visit as a result of the COVID-19 pandemic (self-quarantine or disruption of study site activities 
following business continuity plans and/or local government mandates for “stay at home” or “shelter in place”), a safety call to the participant should be made in 
place of the study site visit. The safety call should encompass all scheduled visit assessments that can be completed remotely, such as assessment for AEs and 
concomitant medications (eg, as defined in scheduled biweekly safety phone calls). Home visits will be permitted for all non-dosing visits except for Screening 
if a participant cannot come to the study site as a result of the COVID-19 pandemic. 
1. 
Day 0 and OL-D1 visit may be performed on 2 separate visits. 
2. 
Symptom-directed physical examination will be performed at the PDV. On dosing day before injection, the arm receiving the injection should be examined 
and the associated lymph nodes should be evaluated. Any clinically significant finding identified during a study visit should be reported as an MAAE. 
Vital signs are to be collected pre- and post-dosing on the days of injection (OL-D1). Participants who are febrile (body temperature ≥ 38.0°C/100.4°F) 
before dosing (OL-D1) must be rescheduled within the relevant window period to receive the injection. Afebrile participants with minor illnesses can be 
enrolled at the discretion of the investigator. 
3. 
Pregnancy test at the PDV will be a point-of-care urine test. At the discretion of the investigator, a pregnancy test either via blood or point-of-care urine 
test can be performed. Follicle-stimulating hormone level may be measured to confirm menopausal status at the discretion of the investigator. 
4. 
Sample must be collected prior to unblinding and injection at the PDV.  
5. 
Post-dosing, participants will have a 30-minute observation period. 
6. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to 
include an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to collect 
the NP sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study site by 
a Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. An 
additional NP swab sample will be collected to test for the presence of other respiratory pathogens. In addition, the study site may collect an additional 
(local/non-central) respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as determined by 
local standards of care. Additionally, clinical information will be carefully collected to evaluate the severity of the clinical case. It is important to note that 
some of the symptoms of COVID-19 overlap with solicited systemic ARs that are expected after vaccination with mRNA-1273 (eg, myalgia, headache, 
fever, and chills). During the first 7 days after vaccination, when these solicited ARs are common, investigators should use their clinical judgement to 
decide if an NP swab should be collected. The collection of an NP swab prior to the PDV can help ensure that cases of COVID-19 are not overlooked. 
Any study participant reporting respiratory symptoms during the 7-day period after vaccination should be evaluated for COVID-19. 
7. 
Trained study personnel will call all participants to collect information relating to any MAAEs (including any signs and symptoms of COVID-19), AEs 
leading to withdrawal, SAEs, information on concomitant medications associated with those events, and any non-study vaccinations.  
8. 
All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759).  
 

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Table 23: 
Part C Supplemental Schedule of Events: Booster Dose Phase 
NOTE: The Part C Supplemental Schedule of Events is to be used for all participants currently enrolled in Part B and who are eligible 
for Part C. As this Supplemental SoE is intended to occur in addition to and in parallel with the original SoEs (Table 16, Table 17, 
Table 18, and Table 19), there is a possibility for study visits to overlap. If visits overlap according to respective visit windows, a single 
visit may be done with the combined study procedures completed once. 
Visit Number 
BD-1 
BD-1a 
 
BD-2 
BD-3 
Type of Visit 
C 
C 
SC10 
C 
C 
Study Visit Day  
BD-D11 
BD-D4 
7, 14, and 21 days 
after  
BD-D1: 
(BD-D8, BD-D15, 
BD-D22) 
BD-D29 
BD-D181 
Window Allowance (Days) 
- 
-2 
+3 
-3/+14 
±14 
Days Since Most Recent Vaccination (in Part C, if applicable) 
0 
3 
7, 14, 21 
28 
180 
Confirm signing of ICF, concomitant medications, medical history 
X 
 
 
 
 
Confirm participant meets inclusion and exclusion criteria 
X 
 
 
 
 
Physical examination2 
X 
 
 
X 
X 
Pregnancy testing3 
X 
 
 
 
 
Immunogenicity Assessment 
 
 
 
 
 
Blood for immunologic analysis 
X4 
 
 
X 
X 
Biomarker Assessment 
 
 
 
 
 
Blood sample for potential biomarker analysis5 
 
X 
 
 
 
Dosing 
 
Study injection (including 30-minute post-dosing observation period6) 
X 
 
 
 
 
Efficacy Assessment 
 
Surveillance for COVID-19/Unscheduled Visit7 
X 
 
X 
X 
X 

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NOTE: The Part C Supplemental Schedule of Events is to be used for all participants currently enrolled in Part B and who are eligible 
for Part C. As this Supplemental SoE is intended to occur in addition to and in parallel with the original SoEs (Table 16, Table 17, 
Table 18, and Table 19), there is a possibility for study visits to overlap. If visits overlap according to respective visit windows, a single 
visit may be done with the combined study procedures completed once. 
Visit Number 
BD-1 
BD-1a 
 
BD-2 
BD-3 
Type of Visit 
C 
C 
SC10 
C 
C 
Study Visit Day  
BD-D11 
BD-D4 
7, 14, and 21 days 
after  
BD-D1: 
(BD-D8, BD-D15, 
BD-D22) 
BD-D29 
BD-D181 
Window Allowance (Days) 
- 
-2 
+3 
-3/+14 
±14 
Days Since Most Recent Vaccination (in Part C, if applicable) 
0 
3 
7, 14, 21 
28 
180 
Nasopharyngeal swab8 
X 
 
 
 
 
Safety Assessments 
 
 
Follow-up safety9,10 
 
 
X 
 
 
Recording of unsolicited AEs10 
X 
X 
X 
X 
 
Recording of MAAEs, AESIs, AE leading to withdrawal and concomitant medications 
relevant to or for the treatment of the MAAE11 
X 
X 
X 
X 
X 
Recording of SAEs and concomitant medications relevant to or for the treatment of the 
SAE11  
X 
X 
X 
X 
X 
Recording of concomitant medications and non-study vaccinations11 
X 
X 
X 
X 
X 

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Abbreviations: AE = adverse event; AESI = adverse event of special interest; BD = booster dose; C = clinic visit; COVID-19 = coronavirus disease 2019; 
D = day; FDA = Food and Drug Administration; ICF = informed consent form; MAAE = medically attended AE; NP= nasopharyngeal swab; RT-PCR = reverse 
transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety (phone) 
call; SoE = Schedule of Events. 
Note: In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the COVID-19 Pandemic (DHHS 2020a), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. All scheduled study visits should be completed within the respective visit windows. 
If the participant is not able to come on-site for a study site visit as a result of the COVID-19 pandemic (self-quarantine or disruption of study site activities 
following business continuity plans and/or local government mandates for “stay at home” or “shelter in place”), a safety call to the participant should be made in 
place of the study site visit. The safety call should encompass all scheduled visit assessments that can be completed remotely, such as assessment for AEs and 
concomitant medications (eg, as defined in scheduled biweekly safety phone calls). Home visits will be permitted for all non-dosing visits except for Screening 
if a participant cannot come to the study site as a result of the COVID-19 pandemic.  
1. 
A BD may be administered to all participants who are currently enrolled in Part B and have received at least 1 dose of mRNA-1273, provided there are 
no current contraindications for further dosing (Section 7).  
2. 
For participants who receive a BD, symptom-directed physical examination will be performed at the BD-1 visit. On dosing day before injection, the arm 
receiving the injection should be examined and the associated lymph nodes should be evaluated. At visits BD-2 (BD-Day 29) and BD-3 (BD-Day 181), 
a symptom-directed physical examination may be performed at the discretion of the investigator. Any clinically significant finding identified during a 
study visit should be reported as an MAAE. For participants who receive a BD, vital signs are to be collected pre- and post-dosing (participant will be 
seated for at least 5 minutes before all measurements are taken per Section 8.2.5) on the day of injection (BD-Day 1). Participants who are febrile (body 
temperature ≥ 38.0°C/100.4°F) before dosing (BD-Day 1) must be rescheduled to receive the injection. Afebrile participants with minor illnesses can be 
vaccinated at the discretion of the investigator. Physical examination and vital sign collection are optional for participants who chose not to receive a 
BD. 
3. 
For participants who receive a BD, the pregnancy test at the BD-1 visit will be a point-of-care urine test. At the discretion of the investigator, a 
pregnancy test either via blood or point-of-care urine test can be performed. Follicle-stimulating hormone level may be measured to confirm menopausal 
status at the discretion of the investigator 
4. 
Sample must be collected prior to injection (if receiving a booster) at the BD-1 visit. 
5. 
Only for participants who chose to receive a BD. Serum sample from two ~4 mL optional blood draws, subject to availability of blood draw kits, and 
will be confirmed with participant at time of re-consenting for Part C. Biomarker plasma and biomarker serum samples will be stored for potential 
future biomarker assessment. 
6. 
Post-dosing, participants will have a 30-minute observation period. 
7. 
Participants with symptoms of COVID-19 will be asked to return within 72 hours or as soon as possible to the study site for an unscheduled visit, to 
collect an NP swab sample (for RT-PCR testing) and other clinical evaluations. If a study site visit is not possible, a home visit may be arranged to 
collect the NP sample and conduct clinical evaluations. If a home visit is not possible, the participant will be asked to submit a saliva sample to the study 
site by a Sponsor-approved method. At this visit, an NP swab and blood sample will be collected to evaluate for the presence of SARS-CoV-2 infection. 
An additional NP swab sample will be collected to test for the presence of other respiratory pathogens. In addition, the study site may collect an 
additional respiratory sample for SARS-CoV-2 testing to be able to render appropriate medical care for the study participant as determined by local 

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standards of care. Additionally, clinical information will be carefully collected to evaluate the severity of the clinical case. Any study participant 
reporting respiratory symptoms during the 7-day period after vaccination should be evaluated for COVID-19. 
8. 
The NP swab sample is strongly encouraged but ultimately optional for the participants. If collected, it must be collected prior to injection at the BD-1 
visit.  
9. 
Trained study personnel will call all participants to collect information relating to any unsolicited AEs, MAAEs (including any signs and symptoms of 
COVID-19), AESIs, AEs leading to withdrawal, SAEs, information on concomitant medications associated with those events, and any non-study 
vaccinations. 
10. Only for participants who chose to receive a BD. 
11. All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Screening through the final visit (Day 759). 
 

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11.2. 
APPENDIX 2: Study Governance Considerations 
11.2.1. 
Regulatory and Ethical Considerations 
This study will be conducted in accordance with the protocol and with the following: 
• Consensus ethical principles derived from international guidelines including the 
Declaration of Helsinki and Council for International Organizations of Medical Sciences 
International Ethical Guidelines. 
• Applicable ICH GCP Guidelines. 
• Applicable laws and regulatory requirements. 
• The protocol, protocol amendments, ICF, Investigator Brochure, and other relevant 
documents (eg, advertisements) must be submitted to an IRB/IEC by the investigator and 
reviewed and approved by the IRB/IEC before the study is initiated. 
• Any amendments to the protocol will require IRB/IEC approval before implementation of 
changes made to the study design, except for changes necessary to eliminate an 
immediate hazard to study participants. 
• The investigator will be responsible for the following: 
− Providing written summaries of the status of the study to the IRB/IEC annually or more 
frequently in accordance with the requirements, policies, and procedures established by the 
IRB/IEC 
− Notifying the IRB/IEC of SAEs or other significant safety findings as required by IRB/IEC 
procedures 
− Providing oversight of the conduct of the study at the site and adherence to requirements of 
21 CFR, ICH guidelines, the IRB/IEC, European regulation 536/2014 for clinical studies (if 
applicable), and all other applicable local regulations. 
11.2.2. 
Study Monitoring 
Before an investigational site can enter a participant into the study, a representative of Moderna or 
its representatives will visit the investigational study site to: 
• Determine the adequacy of the facilities. 
• Discuss with the investigator(s) and other personnel their responsibilities with regard to 
protocol adherence, and the responsibilities of Moderna or its representatives. This will 
be documented in a Clinical Study Agreement between Moderna, designated CRO, and 
the investigator. 

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According to ICH GCP guideline, the Sponsor of the study is responsible for ensuring the proper 
conduct of the study with regard to protocol adherence and validity of data recorded on the eCRFs. 
The study monitor’s duties are to aid the investigator and Moderna in the maintenance of complete, 
accurate, legible, well-organized, and easily retrievable data. The study monitor will advise the 
investigator of the regulatory necessity for study-related monitoring, audits, IRB/IEC review, and 
inspection by providing direct access to the source data/documents. In addition, the study monitor 
will explain to and interpret for the investigator all regulations applicable to the clinical evaluation 
of an IP as documented in ICH guidelines. 
It is the study monitor’s responsibility to inspect the eCRFs and source documentation throughout 
the study to protect the rights of the participants; to verify adherence to the protocol; to verify 
completeness, accuracy, and consistency of the data; and to confirm adherence of study conduct 
to any local regulations. Details will be outlined in the Clinical Monitoring Plan. During the study, 
a monitor from Moderna or a representative will have regular contacts with the investigational site, 
for the following: 
• Provide information and support to the investigator(s). 
• Confirm that facilities remain acceptable. 
• Confirm that the investigational team is adhering to the protocol, that the data are being 
accurately recorded in the eCRFs, and that IP accountability checks are being performed. 
• Perform source data verification. This includes a comparison of the data in the eCRFs 
with the participant’s medical records at the hospital or practice, and other records 
relevant to the study. This will require direct access to all original records for each 
participant (eg, clinical charts or electronic medical record system). 
• Record and report any protocol deviations not previously sent. 
• Confirm AEs and SAEs have been properly documented on eCRFs and confirm any 
SAEs have been forwarded to the SAE Hotline, and those SAEs that met criteria for 
reporting have been forwarded to the IRB/IEC. 
The monitor will be available between visits if the investigator(s) or other staff needs information 
or advice. 
In accordance with FDA Guidance on Conduct of Clinical Trials of Medical Products during the 
COVID-19 Pandemic (DHHS 2020a), investigators may convert study site visits to telemedicine 
visits with the approval of the Sponsor (Section 8 for Procedures). 
The DSMB will also have responsibility for safety monitoring (Section 8.4.2). 

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11.2.3. 
Audits and Inspections 
Moderna, their designee(s), the IRB/IEC, or regulatory authorities will be allowed to conduct site 
visits to the investigational facilities for the purpose of monitoring or inspecting any aspect of the 
study. The investigator agrees to allow Moderna, their designee(s), the IRB/IEC, or regulatory 
authorities to inspect the IP storage area, IP stocks, IP records, participant charts and study source 
documents, and other records relative to study conduct. 
Authorized representatives of Moderna, a regulatory authority, and any IRB/IEC may visit the site 
to perform audits or inspections, including source data verification. The purpose of a Sponsor audit 
or inspection is to systematically and independently examine all study-related activities and 
documents to determine whether these activities were conducted, and data were recorded, 
analyzed, and accurately reported according to the protocol, ICH GCP E6R2, and any applicable 
regulatory requirements. The investigator should contact Moderna immediately if contacted by a 
regulatory agency about an inspection. 
The Principal Investigator must obtain IRB approval for the investigation. Initial IRB approval, 
and all materials approved by the IRB for this study including the participant consent form and 
recruitment materials must be maintained by the investigator and made available for inspection. 
11.2.4. 
Financial Disclosure 
The investigator is required to provide financial disclosure information to allow the Sponsor to 
submit the complete and accurate certification or disclosure statements required under 21 CFR 54. 
In addition, the investigator must provide the Sponsor with a commitment to promptly update this 
information if any relevant changes occur during the course of the investigation and for 1 year 
following the completion of the study. 
The Sponsor, the CRO, and the study site are not financially responsible for further testing or 
treatment of any medical condition that may be detected during the screening process. In addition, 
in the absence of specific arrangements, the Sponsor, the CRO, and the study site are not 
financially responsible for further treatment of the disease under study. 
11.2.5. 
Recruitment Procedures 
Advertisements to be used for the recruitment of study participants, and any other written 
information regarding this study to be provided to the participant should be submitted to the 
Sponsor for approval. All documents must be approved by the IRB. 
11.2.6. 
Informed Consent Process 
The informed consent document(s) must meet the requirements of 21 CFR 50, local regulations, 
ICH guidelines, Health Insurance Portability and Accountability Act requirements, where 

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applicable, and the IRB/IEC or study center. All consent documents will be approved by the 
appropriate IRB/IEC. The actual ICF used at each center may differ, depending on local 
regulations and IEC/IRB requirements. However, all versions must contain the standard 
information found in the sample ICF provided by the Sponsor. Any change to the content of the 
ICF must be approved by the Sponsor and the IEC / IRB prior to the form being used. 
If new information becomes available that may be relevant to the participant’s willingness to 
continue participation in the study, this will be communicated to him/her in a timely manner. Such 
information will be provided via a revised ICF or an addendum to the original ICF. 
The investigator or his/her representative will explain the nature of the study to the participant and 
answer all questions regarding the study. 
The investigator is responsible for ensuring that the participant fully understands the nature and 
purpose of the study. Information should be given in both oral and written form whenever possible. 
No participant should be obliged to participate in the study. The participant must be informed that 
participation is voluntary. Participants, their relatives, guardians, or (if applicable) legal 
representatives must be given ample opportunity to inquire about details of the study. The 
information must make clear that refusal to participate in the study or withdrawal from the study 
at any stage is without any prejudice to the participant’s subsequent care. 
The participant must be allowed sufficient time to decide whether they wish to participate. The 
participant must be made aware of and give consent to direct access to his/her source medical 
records by study monitors, auditors, the IRB/IEC, and regulatory authorities. The participant 
should be informed that such access will not violate participant confidentiality or any applicable 
regulations. The participant should also be informed that he/she is authorizing such access by 
signing the ICF. 
A copy of the ICF(s) must be provided to the participant. 
A participant who is rescreened/rescheduled (including at the BD-1 visit) is not required to re-sign 
the same version of the ICF if this occurs within 28 days from the previous ICF signature date. 
The ICF will also explain that excess serum from immunogenicity testing may be used for future 
research, which may be performed at the discretion of the Sponsor to further characterize the 
immune response to SARS-CoV-2, additional assay development, and the immune response across 
CoV. 
11.2.7. 
Protocol Amendments 
No change or amendment to this protocol may be made by the investigator or the Sponsor after 
the protocol has been agreed to and signed by all parties unless such change(s) or amendment(s) 

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has (have) been agreed upon by the investigator or the Sponsor. Any change agreed upon will be 
recorded in writing, and the written amendment will be signed by the investigator and the Sponsor. 
Institutional review board approval is required prior to the implementation of an amendment, 
unless overriding safety reasons warrant immediate action, in which case the IRB(s)/IEC(s) will 
be promptly notified. 
Any modifications to the protocol or the ICF, which may impact the conduct of the study, potential 
benefit of the study, or may affect participant safety, including changes of study objectives, study 
design, participant population, sample sizes, study procedures, or significant administrative 
aspects will require a formal amendment to the protocol. Such amendment will be released by the 
Sponsor, agreed by the investigator(s), and approved by the relevant IRB(s)/IEC(s) prior to 
implementation. A signed and dated statement that the protocol, any subsequent relevant amended 
documents and the ICF have been approved by relevant IRB(s)/IEC(s) must be provided to the 
Sponsor before the study is initiated. 
Administrative changes of the protocol are minor corrections and/or clarifications that have no 
effect on the way the study is to be conducted. These administrative changes will be released by 
the Sponsor, agreed by the investigator(s), and notified to the IRB(s)/IEC(s). 
11.2.8. 
Protocol Deviations 
The noncompliance may be either on the part of the participant, the investigator, or the study site 
staff. As a result of deviations, corrective actions are to be developed by the site and implemented 
promptly. 
It is the responsibility of the site investigator to use continuous vigilance to identify and report 
deviations to the Sponsor or its designee. All deviations must be addressed in study source 
documents, reported to study monitor. Protocol deviations must be sent to the reviewing IRB/IEC 
per their policies. The site investigator is responsible for knowing and adhering to the reviewing 
IRB/IEC requirements. 
11.2.9. 
Data Protection 
Participants will be assigned a unique identifier by the Sponsor. Any participant records or datasets 
that are transferred to the Sponsor will contain the identifier only; participant names or any 
information which would make the participant identifiable will not be transferred. 
The participant must be informed that his/her personal study-related data will be used by the 
Sponsor in accordance with local data protection law. The level of disclosure must also be 
explained to the participant. 

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The participant must be informed that his/her medical records may be examined by Clinical 
Quality Assurance auditors or other authorized personnel appointed by the Sponsor, by appropriate 
IRB/IEC members, and by inspectors from regulatory authorities. 
Individual participant medical information obtained as a result of this study is considered 
confidential, and disclosure to third parties is prohibited. Information will be accessible to 
authorized parties or personnel only. Medical information may be given to the participant’s 
physician or to other appropriate medical personnel responsible for the participant’s well-being. 
Each participant will be asked to complete a form allowing the investigator to notify the 
participant’s primary health care provider of his/her participation in this study. 
All laboratory specimens, evaluation forms, reports, and other records will be identified in a 
manner designed to maintain participant confidentiality. All records will be kept in a secure 
storage area with limited access. Clinical information will not be released without the written 
permission of the participant, except as necessary for monitoring and auditing by the Sponsor, 
its designee, relevant regulatory authority, or the IRB. 
The investigator and all employees and coworkers involved with this study may not disclose or use 
for any purpose other than performance of the study, any data, record, or other unpublished, 
confidential information disclosed to those individuals for the purpose of the study. Prior written 
agreement from the Sponsor or its designee must be obtained for the disclosure of any confidential 
information to other parties. 
11.2.10. 
Sample Retention and Future Biomedical Research 
The retention period of laboratory samples will be 15 years, or as permitted by local regulations, 
to address further scientific questions related to mRNA-1273 or anti-respiratory virus immune 
response. In addition, identifiable samples can be destroyed at any time at the request of the 
participant. During the study, or during the retention period, in addition to the analysis outlined in 
the study endpoints, exploratory analysis may be conducted, using other Ab-based methodologies, 
on any remaining blood or serum samples, including participants who provide samples for 
screening, but are not subsequently enrolled. These analyses would extend the search for other 
potentially relevant biomarkers to investigate the effect of mRNA-1273, as well as to determine 
how changes in the markers may relate to exposure and clinical outcomes. A decision to perform 
such exploratory research may arise from new scientific findings related to the drug class or 
disease, as well as reagent and assay availability. 

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11.2.11. 
Data Quality Assurance and Quality Control 
Data collection is the responsibility of the clinical study staff at the site under the supervision of 
the site investigator. The investigator is responsible for ensuring the accuracy, completeness, 
legibility, and timeliness of the data reported. 
• All participant data relating to the study will be recorded eCRF unless transmitted to 
the Sponsor or designee electronically (eg, laboratory data). The investigator is 
responsible for verifying that data entries are accurate and correct by physically or 
electronically signing the eCRF. 
• The investigator must maintain accurate documentation (source data) that supports 
the information entered in the eCRF. 
• The investigator must permit study-related monitoring, audits, IRB/IEC review, and 
regulatory agency inspections and provide direct access to source data documents. 
• Monitoring details describing strategy (eg, risk-based initiatives in operations and 
quality such as Risk Management and Mitigation Strategies and Analytical 
Risk-Based Monitoring), methods, responsibilities and requirements, including 
handling of noncompliance issues and monitoring techniques (central, remote, or 
on-site monitoring) are provided in the study Monitoring Plan, Centralized 
Monitoring Plan, and Risk Management Plan. 
• The Sponsor or designee is responsible for the data management of this study 
including quality checking of the data. 
• The Sponsor assumes accountability for actions delegated to other individuals (eg, 
CROs). 
• Study monitors will perform ongoing source data verification to confirm that data 
entered into the eCRF by authorized site personnel are accurate, complete, and 
verifiable from source documents; that the safety and rights of participants are being 
protected; and that the study is being conducted in accordance with the currently 
approved protocol and any other study agreements, ICH GCP, and all applicable 
regulatory requirements. 
• Records and documents, including signed ICFs, pertaining to the conduct of this 
study must be retained by the investigator for 15 years after study completion unless 
local regulations or institutional policies require a longer retention period. No records 
may be destroyed during the retention period without the written approval of the 
Sponsor. No records may be transferred to another location or party without written 
notification to the Sponsor. 

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Quality assurance (QA) includes all the planned and systematic actions that are established to 
ensure that the clinical study is performed, and the data are generated, documented (recorded), and 
reported according to ICH GCP and local/regional regulatory standards. 
A QA representative from the Sponsor or qualified designee, who is independent of and separated 
from routine monitoring, may periodically arrange inspections/audits of the clinical study by 
reviewing the data obtained and procedural aspects. These inspections may include on-site 
inspections/audits and source data checks. Direct access to source documents is required for the 
purpose of these periodic inspections/audits. 
11.2.12. 
Data Collection and Management 
This study will be conducted in compliance with ICH CGP guidelines. This study will also be 
conducted in accordance with the most recent version of the Declaration of Helsinki. 
This study will use electronic data collection (to collect data directly from the investigational site 
using eCRFs). The investigator is responsible for ensuring that all sections of each eCRF are 
completed promptly and correctly and that entries can be verified against any source data. 
Study monitors will perform source document verification to identify inconsistencies between the 
eCRFs and source documents. Discrepancies will be resolved in accordance with the principles of 
GCP. Detailed study monitoring procedures are provided in the Clinical Monitoring Plan. 
AEs will be coded with the most current available version of MedDRA. Concomitant medications 
will be coded using WHO – Drug Reference List. 
11.2.13. 
Source Documents 
Source documents are original documents or certified copies, and include, but are not limited to, 
diaries, medical and hospital records, screening logs, informed consent/assent forms, telephone 
contact logs, and worksheets. Source documents provide evidence for the existence of the 
participant and substantiate the integrity of the data collected. Source documents are filed at the 
investigator’s site. 
Data reported on the CRF or entered in the eCRF that are transcribed from source documents must 
be consistent with the source documents or the discrepancies must be explained. The investigator 
may need to request previous medical records or transfer records, depending on the study. Also, 
current medical records must be available. 
Moderna or its designee requires that the investigator prepare and maintain adequate and accurate 
records for each participant treated with the IP. Source documents such as any hospital, clinic, or 
office charts and the signed ICFs are to be included in the investigator’s files with the participant’s 
study records. 

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11.2.14. 
Retention of Records 
The Principal Investigator must maintain all documentation relating to the study for a period of at 
least 2 years after the last marketing application approval or, if not approved, 2 years following 
the discontinuance of the test article for investigation. If this requirement differs from any local 
regulations, the local regulations will take precedence unless the local retention policy is less than 
2 years. 
If it becomes necessary for Moderna or the regulatory authority to review any documentation 
relating to the study, the investigator must permit access to such records. No records will be 
destroyed without the written consent of the Sponsor, if applicable. It is the responsibility of the 
Sponsor to inform the investigator when these documents no longer need to be retained. 
11.2.15. 
Study and Site Closure 
If the study is prematurely terminated or suspended, the Sponsor shall promptly inform the 
investigators, the IECs/IRBs, the regulatory authorities, and any CRO(s) used in the study of the 
reason for termination or suspension, as specified by the applicable regulatory requirements. The 
investigator shall promptly inform the participant and should assure appropriate participant therapy 
and/or follow-up. 
The Sponsor or designee reserves the right to close the study site or terminate the study at any time 
for any reason at the sole discretion of the Sponsor. 
The investigator may initiate study-site closure at any time, provided there is reasonable cause and 
sufficient notice is given in advance of the intended termination. 
Reasons for the early closure of a study site by the Sponsor or investigator may include but are not 
limited to: 
• Continuation of the study represents a significant medical risk to participants. 
• Failure of the investigator to comply with the protocol, the requirements of the 
IRB/IEC or local health authorities, the Sponsor's procedures, or GCP guidelines. 
• Inadequate recruitment of participants by the investigator. 
• Discontinuation of further mRNA-1273 development. 
Study sites will be closed upon study completion. A study site is considered closed when all 
required documents and study supplies have been collected and a study-site closure visit has been 
performed. 

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11.2.16. 
Publication Policy 
The results of this study may be published or presented at scientific meetings. If this is foreseen, 
the investigator agrees to submit all manuscripts or abstracts to the Sponsor before submission. 
This allows the Sponsor to protect proprietary information and to provide comments. 
The Sponsor will comply with the requirements for publication of study results. In accordance 
with standard editorial and ethical practice, the Sponsor will generally support publication of 
multicenter studies only in their entirety and not as individual site data. In this case, a coordinating 
investigator will be designated by mutual agreement. 
Authorship will be determined by mutual agreement and in line with International Committee of 
Medical Journal Editors authorship requirements. 
The clinical study plan and the results of the study will be published on www.ClinicalTrials.gov 
in accordance with 21 CFR 50.25(c). The results of and data from this study belong to Moderna. 

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11.3. 
APPENDIX 3: Contraceptive Guidance 
Woman of Childbearing Potential (WOCBP) 
Females of childbearing potential are those who are considered fertile following menarche and 
until becoming postmenopausal unless permanently sterile (see below). If fertility is unclear (eg, 
amenorrhea in adolescents or athletes) and a menstrual cycle cannot be confirmed before first dose 
of study treatment, additional evaluation should be considered. 
Women in the following categories are not considered WOCBP: 
1. Premenarchal 
2. Premenopausal, surgically sterile female with 1 of the following: 
a. Documented complete hysterectomy 
b. Documented bilateral salpingectomy 
c. Documented bilateral oophorectomy 
For individuals with permanent infertility due to an alternate medical cause other than the above, 
(eg, mullerian agenesis, androgen insensitivity), investigator discretion should be applied in 
determining study entry. 
Note: Documentation can come from the site personnel’s: review of the participant’s medical 
records, medical examination, or medical history interview. 
3. Postmenopausal female 
• A postmenopausal state is defined as no menses for 12 months without an alternative 
medical cause. The following age-specific requirements apply: 
o Women < 50 years of age would be considered postmenopausal if they have been 
amenorrheic for 12 months or more following cessation of exogenous hormonal 
treatments and if they have luteinizing hormone and FSH levels in the 
postmenopausal range for the institution. 
o Women ≥ 50 years of age would be considered postmenopausal if they have been 
amenorrheic for 12 months or more, had radiation-induced menopause with last 
menses > 1 year ago or had chemotherapy-induced menopause with last menses 
> 1 year ago. 
• A high FSH level in the postmenopausal range may be used to confirm a postmenopausal 
state in women not using hormonal replacement therapy (HRT). 
• Females on HRT and whose menopausal status is in doubt will be required to use one of 
the non-estrogen hormonal highly effective contraception methods if they wish to 

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continue their HRT during the study. Otherwise, they must discontinue HRT to allow 
confirmation of postmenopausal status before study enrollment.

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11.4. 
APPENDIX 4: Statistical Appendices 
11.4.1. 
Estimands and Estimand Specifications 
Table 24: 
Intercurrent Event Types 
Label 
Intercurrent Event Type 
Comment 
IcEv1 (death without 
confirmation of cases, ie, 
unrelated death) 
Unrelated death without documented confirmed COVID-19 
Participants in PP Set who die due to reasons 
unrelated to COVID-19 without confirmation of 
being a case will all be included in statistical 
analysis. 
 
IcEv2 (early COVID-19) 
COVID-19 starting up to 14 days after the second dose of IP 
Participants in PP Set who experience early 
COVID-19 up to 14 days after the second dose of IP 
will all be included in statistical analysis. 
Abbreviations: COVID-19 = coronavirus disease 2019; IcEv: intercurrent event; IP = investigational product; PP: per-protocol. 

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Table 25: 
Primary Objective and Estimands With Rationale for Strategies to Address Intercurrent Events for Per-
protocol Analysis 
Objective: To demonstrate the efficacy of mRNA-1273 to prevent COVID-19 
Estimand Description 
Vaccine efficacy will be measured using 1 – HR (mRNA-1273/placebo) of COVID-19 from 14 
days after second dose of IP in adults. A hypothetical strategy will be used for deaths unrelated to 
COVID-19, and a hypothetical strategy will also be used for early COVID-19 in participants in the 
PP Set.  
Target Population 
Adults aged 18 years and older in circumstances at a high risk of SARS-CoV-2 infection but 
without medical conditions that pose additional risk of developing severe disease. 
The population excludes those previously infected or vaccinated for SARS-CoV-2 or with a 
medical condition, on treatment that poses additional risks (including those requiring 
immunosuppressants or immune-modifying drugs), or SARS-CoV-2 pre-positive. 
Variable/Endpoint 
Time to COVID-19 disease, censoring at early discontinuation, early COVID-19, or last 
assessment for an event not being observed, whichever comes earlier. 
 
Treatment Condition(s) 
Test: mRNA-1273 
Reference: Placebo 
Estimand Label 
Estimand 1 
 
Population-Level Summary 
Vaccine efficacy defined as 1 - HR of mRNA-1273/placebo  
Intercurrent Event Strategy  
 
IcEv1 (Unrelated death): 
Hypothetical  
IcEv2 (early infection): 
Hypothetical 
Rationale for Strategy(s) 
Hypothetical: unrelated death without confirmation of COVID-19 will be censored at the time of 
death as if there is no event, handled with independent censoring. 
Hypothetical: early case in PP Set will be censored at the time of case onset if it is not a case, 
handled with independent censoring. 
Abbreviations: COVID-19 = coronavirus disease 2019; HR = hazard ratio; IcEv = intercurrent event; IP = investigational product; PP = per protocol; 
SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2. 

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11.4.2. 
Statistical Methods and Sensitivity Analyses 
Table 26: 
Summary of Statistical Methods and Sensitivity Analyses 
Estimand 
Label 
Estimand 
Description 
Main Estimation 
Sensitivity Analysis 
Analysis Set 
Imputation/Data/Censoring Rules 
Analysis Model/Method 
Estimand 1 
See Table 25  
PP Set 
Participants who did not develop 
COVID-19, ongoing or complete the 
study will be censored at the last 
assessment. 
Participants who discontinue early or 
die without COVID-19 will be 
censored at the date of discontinuation 
or death, respectively. 
Participant who is a confirmed case 
prior to 14 days after the second dose 
of IP will be censored on the date of 
confirmation. 
The (1 - HR) with 95% CI 
will be estimated using Cox 
proportional hazard 
regression analysis with 
treatment arm as a fixed 
effect stratified by 
randomization stratification 
factors. And the null 
hypothesis will be tested 
using Wald Chi-square 
method. 
As described in 
Section 9.5.1 with 
cases counted 
starting after the 
second dose of IP. 
Abbreviations: CI = confidence interval; COVID-19 = coronavirus disease 2019; HR = hazard ratio; IP = investigational product; PP = per protocol. 

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11.5. 
APPENDIX 5: Adverse Events of Special Interest Terms 
The Investigator’s medical judgement must be applied to assess an event as an AESI, as 
most AESIs are based on medical concepts. Table 27 below does not provide a 
comprehensive list of terms.  
Table 27 describes events/medical concepts that are of interest in COVID-19 vaccine safety 
surveillance. Some are specific to vaccines; however, some are of interest due to their occurrence 
in the context of concurrent or recent COVID-19. Events that occur in Part C (after participants 
receive a booster dose) and fall into the descriptions below should be reported as AESIs, per the 
reporting processes specified in Section 8.3.3, even when they occur during/following COVID-
19 infection.  
Please note: COVID-19 itself is not an AESI. 
Table 27: 
Adverse Events of Special Interest 
Medical Concept 
Medical Concept Descriptions/Guidance 
Anosmia, Ageusia 
 
• New onset of anosmia or ageusia associated with COVID-19 or 
idiopathic etiology  
• DOES NOT INCLUDE anosmia or ageusia associated with 
sinus/nasal congestion, congenital, or traumatic etiologies  
Subacute thyroiditis 
 
• Acute inflammatory disease of the thyroid (immune-mediated or 
idiopathic) 
• DOES NOT INCLUDE new onset of chronic thyroiditis 
Acute pancreatitis 
 
• New onset of pancreatitis in the absence of a clear, alternate 
etiology, such as alcohol, gallstones, trauma, recent invasive 
procedure, etc. 
Appendicitis  
• Any event of appendicitis  
Rhabdomyolysis 
 
• New onset of rhabdomyolysis in the absence of a clear, alternate 
etiology, such as drug/alcohol abuse, excessive exercise, trauma, 
etc. 
Acute respiratory 
distress syndrome 
(ARDS) 
• New onset of ARDS/respiratory failure due to acute inflammatory 
lung injury 
• DOES NOT INCLUDE non-specific symptoms of shortness of 
breath or dyspnea, nor events with underlying etiologies of heart 
failure or fluid overload 
Coagulation 
disorders 
• New onset of thrombosis, thromboembolic event, or non-traumatic 
hemorrhage/bleeding disorder (ex. stroke, DVT, pulmonary 
embolism, disseminated intravascular coagulation (DIC), etc.) 

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Medical Concept 
Medical Concept Descriptions/Guidance 
Acute 
cardiovascular 
injury 
• New onset of clinically confirmed, acute cardiovascular injury, such 
as myocarditis, pericarditis, arrhythmia confirmed by ECG (ex. 
atrial fibrillation, atrial flutter, supraventricular tachycardia), stress 
cardiomyopathy, heart failure, acute coronary syndrome, myocardial 
infarction, etc. 
• DOES NOT INCLUDE transient sinus tachycardia/bradycardia, non-
specific symptoms such as palpitations, racing heart, heart fluttering 
or pounding, irregular heartbeats, shortness of breath, chest 
pain/discomfort, etc. 
Acute kidney injury 
• New onset of acute kidney injury or acute renal failure in the 
absence of a clear, alternate etiology, such as urinary tract 
infection/urosepsis, trauma, tumor, nephrotoxic 
medications/substances, etc.; 
• Increase in serum creatinine by ≥ 0.3 mg/dl (or ≥26.5 µmol/l) within 
48 hours; OR 
• Increase in serum creatinine to ≥ 1.5 times baseline, known or 
presumed to have occurred within prior 7 days 
Acute liver injury 
• New onset in the absence of a clear, alternate etiology, such as 
trauma, tumor, hepatotoxic medications/substances, etc.: 
• >3-fold elevation above the upper normal limit for ALT or AST; 
OR 
• >2-fold elevation above the upper normal limit for total serum 
bilirubin or GGT or ALP 
Dermatologic 
findings  
• Chilblain-like lesions 
• Single organ cutaneous vasculitis 
• Erythema multiforme 
• Bullous rash 
• Severe cutaneous adverse reactions, such as Stevens-Johnson 
syndrome, Toxic epidermal necrolysis, Drug reaction with 
eosinophilia and systemic symptoms (DRESS), fixed drug 
eruptions, and necrotic or exfoliative reactions 
Systemic 
inflammatory 
syndromes  
• Multisystem inflammatory syndrome in adults (MIS-A) or children 
(MIS-C) 
• Kawasaki’s disease 
• Hemophagocytic lymphohistiocytosis (HLH) 
Thrombocytopenia 
• Platelet count < 150 x10^9/L (thrombocytopenia) 
• New clinical diagnosis, or worsening, of thrombocytopenic 
condition, such as immune thrombocytopenia, thrombocytopenic 
purpura, or HELLP syndrome 

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Medical Concept 
Medical Concept Descriptions/Guidance 
Acute aseptic 
arthritis  
 
Clinical syndrome characterized by acute onset of signs and symptoms 
of joint inflammation without recent trauma for a period of no longer 
than 6 weeks, synovial increased leukocyte count and the absence of 
microorganisms on Gram stain, routine culture and/or PCR. 
• DOES NOT INCLUDE new onset of chronic arthritic conditions 
New onset, or 
worsening, of 
neurological disease 
• Immune-mediated neurological disorders 
• Guillain-Barre Syndrome 
• Acute disseminated encephalomyelitis (ADEM) 
• Peripheral facial nerve palsy (Bell’s palsy)  
• Transverse myelitis 
• Encephalitis/Encephalomyelitis 
• Aseptic meningitis 
• Seizures/convulsions/epilepsy 
• Narcolepsy/hypersomnia 
Anaphylaxis  
• Anaphylaxis associated with study drug administration 
Other syndromes 
 
• Fibromyalgia  
• Postural Orthostatic Tachycardia Syndrome  
• Chronic Fatigue Syndrome  
• Myalgic encephalomyelitis  
• Post viral fatigue syndrome 
• Myasthenia gravis 
Abbreviations: ALP = alkaline phosphatase; ALT = alanine transaminase; AST = aspartate transaminase; COVID-
19 = coronavirus disease 2019. 
11.6. 
APPENDIX 6: Protocol Amendment History 
The document history table for this protocol and the Protocol Amendment Summary of Changes 
Table for the current Amendment 10 is located directly before the Table of Contents. 
A description of Amendment 9, Amendment 8, Amendment 7, Amendment 6, Amendment 5, 
Amendment 4, Amendment 3, Amendment 2, and Amendment 1 is presented in this appendix. 
Amendment 9, 10 Sep 2021 
Main Rationale for the Amendment: 
1. To provide a 50 µg BD of mRNA-1273 to participants. This change is prompted by the 
announcement by the President of the US that, as of 20 Sep 2021, certain individuals will 
be eligible to receive a BD in addition to the prior receipt of a primary vaccine regimen 
with mRNA-1273. The interim results of an ongoing Moderna Phase 2 study 
(mRNA-1273-P201), in which participants who 6 to 8 months prior received 2 doses of 

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50 µg or 100 µg of mRNA-1273 were administered a 50 µg booster of mRNA-1273, 
demonstrated enhanced immune responses compared to pre-boost levels and met the 
noninferiority criteria stipulated in the FDA Guidance on EUA for Vaccines to Prevent 
COVID-19. Additionally, no new safety signals emerged upon administration of the BD in 
Study mRNA-1273-P201. Based on cumulative evidence, the benefit-risk profile of a BD 
of mRNA-1273 is favorable, particularly in light of increasing breakthrough disease with 
the emergence of the Delta variant. The details of eligibility for BDs provided by the US 
federal government have not been specified as of the time of writing this protocol 
amendment. Providing the option for a BD to all federally eligible participants currently 
enrolled in Part B is expected to promote retention of participants in the ongoing study and 
thereby defend the scientific integrity of the study for the planned 2-year duration of 
follow-up after the completion of the primary vaccination series. 
2. To provide guidance to the investigators regarding assessing and reporting AESIs, 
including myocarditis and pericarditis, for this study population. 
Summary of Major Changes From Protocol Amendment 8 to Protocol Amendment 9:  
Section # and Name 
Description of Change 
Brief Rationale 
Section 1.2 (Schema); Section 4.1 
(General Design); Section 4.1.3 (Part C, 
the Booster Dose Phase); Section 4.3 
(Choice of Dose and Control Product); 
Section 5.1.1 (Inclusion Criteria); 
Section 6.2.2 (Administration of 
Investigational Product); Section 6.2.4 
(Packaging and Labeling); Section 6.2.5 
(Storage); Section 8.1.2 (Surveillance for 
COVID-19 Symptoms); Section 8.1.5 
(Immunogenicity Assessments); 
Section 8.2 (Safety Assessments); 
Section 8.2.1 (Safety Phone Calls); 
Section 8.2.6 (Blood Sampling); 
Section 8.3.6 (Recording and Follow-up of 
Pregnancy); Section 8.3.7 (Recording and 
Follow-up of an AE and/or SAE); 
Section 9 (Statistical Considerations); 
Section 9.5.1.3 (Long-term Efficacy 
Analysis); Section 9.5.2.1 (Adverse 
Events); Section 11.1. (APPENDIX 1: 
Schedules of Events; Table 23) 
Text updated to reflect initiation 
of Part C, providing for 
administration of an mRNA-1273 
booster dose.  
To promote retention of 
participants in the ongoing 
study and thereby defend the 
scientific integrity of the study 
for the planned 2-year duration 
of follow-up after completion 
of the primary vaccination 
series. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 2.1 (Study Rationale); 
Section 2.2.2 (Clinical Studies); 
Section 2.3.2 (Risks from Study 
Participation) 
Updated the status of ongoing 
clinical research studies. 
To provide context for Protocol 
Amendment 9. 
Section 2.3.2 (Risks from Study 
Participation) 
Updated to include no clinical 
evidence for enhanced vaccine 
disease from the Phase 3 clinical 
trial. Also updated to include very 
rare reports of myocarditis and 
pericarditis occurring after 
vaccination with Moderna 
COVID-19 vaccine. 
To provide updated information 
to the investigators in line with 
updates made to the IB. 
Section 3 (Objectives and Endpoints) 
Updated to include evaluation of 
the safety and immunogenicity of 
a booster dose of mRNA-1273 as 
exploratory objectives. 
To identify objectives related to 
the initiation of Part C.  
Section 8.1.1 (Efficacy Assessments 
Related to COVID-19 and SARS-CoV-2 
Infection) 
Definition of seroconversion for 
participants seropositive at 
Baseline has been deleted. 
Seroconversion in participants 
seropositive at Baseline was not 
assessed for the Part A Blinded 
Phase and will not be assessed 
for Part B or Part C. 
Section 8.1.2 (Surveillance for COVID-19 
Symptoms); Section 11.1 (Appendix 1: 
Schedules of Events) 
Clarified that 2 NP swab samples 
are collected at Illness Visits. 
To enhance consistency of data 
collection at study sites. 
Section 8.3.3 (Adverse Events of Special 
Interest); Section 10 (References); 
Section 11.5 (Appendix 5: Adverse Events 
of Special Interest Terms) 
Added CDC case definitions for 
myocarditis and pericarditis, as 
well as other terms for other 
potentially relevant adverse 
events of special interest. 
To provide guidance to the 
investigators regarding 
assessing and reporting adverse 
events of special interest, 
including myocarditis and 
pericarditis, for this study 
population. 
Section 8.4.4 (Independent Cardiac Event 
Adjudication Committee) 
Added Section 8.4.4, Independent 
Cardiac Event Adjudication 
Committee. 
To describe the proposed 
mechanism to assess risk of 
myocarditis and pericarditis in 
the study population (to address 
Center for Biologics Evaluation 
and Research [CBER] request 
to describe how risk of 
myocarditis and pericarditis 
will be assessed in the study 
population receiving 
mRNA-1273). 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.8 (Exploratory Assessments and 
Biomarkers)  
Text updated to reflect initiation 
of Part C of the study. 
To reflect more 
comprehensively the current 
thinking on potential 
exploratory assessments. 
Section 9.5.3 (Immunogenicity Analyses) 
A definition of seroresponse was 
added.  
To more clearly define the 
relevant antibody response.  
Section 11.1 (Appendix 1: Schedules of 
Events; Table 17 and Table 18) 
Adjusted the collection of eDiary 
data to be weekly from Day 64 
through Day 759. 
To ensure no gap in eDiary data 
collection, as they run weekly, 
regardless of scheduled study 
site visits or safety calls. 
Section 11.1 (Appendix 1: Schedules of 
Events; Table 18) 
Reduced the frequency of safety 
calls from every month after 
Visit 5 (Month 13) to every 
2 months after Visit 5. 
To reduce participant burden. 
COVID-19 and safety 
surveillance will be maintained 
through the continued weekly 
surveillance by eDiary during 
the second year of the 
Surveillance Phase. 
Amendment 8, 23 Mar 2021 
Main Rationale for the Amendment: 
The purpose of this amendment is to update language around unblinding and open-label dosing in 
the context of the majority of participants already having completed their blinded follow-up. In 
addition, the amendment updates the reporting of serious COVID-19 cases.  
The summary of changes table provided here describes the major changes made in Amendment 8 
relative to Amendment 7, including the sections modified and the corresponding rationales. As 
applicable, the synopsis of Amendment 8 has been modified to correspond to changes in the body 
of the protocol. 
Summary of Major Changes From Protocol Amendment 7 to Protocol Amendment 8:  

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Section # and Name 
Description of Change 
Brief Rationale 
Section 4.1.2 (Part B, the Open-Label 
Observational Phase) 
States that, due to ethical and 
scientific concerns, all 
participants will be unblinded 
once investigational product is no 
longer available. In addition, the 
text indicates that if participants 
want to receive Emergency Use 
Authorization (EUA) vaccine 
outside of the study, participants 
will need to be withdrawn from 
the study. 
The amendment also provides 
directions for unblinding after 
Biologics License Application 
(BLA) database lock. 
At the time of this amendment, 
more than 95% of the enrolled 
participants have completed 
blinded follow-up, either 
through being unblinded or 
study discontinuation. 
Therefore, there is no scientific 
value for participants to remain 
blinded. 
In addition, non-study EUA 
vaccines are widely available, 
so ethically, participants should 
be unblinded to ensure they can 
make an informed choice if 
they wish to receive EUA 
COVID-19 vaccine outside of 
the study. 
Section 8.3.7 (Time Period and Frequency 
for collecting Adverse Events and Serious 
Adverse Event Information) and Section 
8.3.10 (Reporting Adverse Events) 
Reporting of only serious 
COVID-19 cases within 24 hours 
to Sponsor or it's designee. 
Nonserious COVID-19 cases 
are an efficacy endpoint, so 
reporting to Pharmacovigilance 
is no longer warranted. 
 
Amendment 7, 10 Feb 2021 
Main Rationale for the Amendment: 
The purpose of this amendment is to collect safety information on suspected cases of anaphylaxis 
and to include participant history of facial injections or dermal fillers in the eDiary.  
The summary of changes table provided here describes the major changes made in Amendment 7 
relative to Amendment 6, including the sections modified and the corresponding rationales. The 
synopsis of Amendment 7 has been modified to correspond to changes in the body of the protocol. 
Summary of Major Changes From Protocol Amendment 6 to Protocol Amendment 7:  
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and 
date. 
To reflect the new version and date 
of the protocol. 

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Section # and Name 
Description of Change 
Brief Rationale 
Sections 1.1 (Synopsis), 
6.2.2 (Administration of 
Investigational Product), 
6.2.8.1 (Planned Unblinding) 
Clarified that study site personnel 
who were blinded during the 
Blinded Phase will be unblinded 
at the participant level at the 
Participant Decision clinic visit. 
To clarify that the site personnel is 
being unblinded only at the 
Participant Decision clinic visit. 
Sections 1.1 (Synopsis), 4.1.2 (Part B, 
the Open-Label Observational Phase) 
Clarified that with regard to EUA 
eligibility in Part B, the 
CDC-EUA guidance 
specifications will supersede 
eligibility criteria in the protocol. 
To clarify that the CDC-EUA 
guidance specifications supersede 
protocol-specified criteria for EUA 
eligibility in Part B. 
Section 4.1 (General Design) 
Corrected the number of 
scheduled clinic visits and added 
mention of the participant 
decision visit.  
To clarify the number of scheduled 
visits.  
Section 4.1.2 (Part B, the Open-Label 
Observational Phase) 
Updated text to clarify 
requirements for Part B subjects 
who are unblinded and received 
only 1 dose of mRNA-1273 
during Part A. 
Clarification of requirements for 
Part B subjects who received only 
1 dose of mRNA-1273 during 
Part A. 
Section 6.2.4 (Packaging and 
Labeling) 
Updated to indicate that vaccine 
product is packaged in a 10R 
glass vial with a 6-dose, 5.0-mL 
or 10-dose, 6.3-mL fill volume. 
To include IP presentation for 
additional supplies that may be used 
in Part B of the study. 
Section 6.2.5 (Storage) 
Updated to specify storage 
requirements for the 6-dose and 
10-dose mRNA vaccine.  
To include IP storage conditions for 
additional supplies that may be used 
in Part B of the study. 
Sections 6.4.2 (Concomitant 
Medications and Therapies), 
7.2 (Discontinuation of Study 
Treatment), 8.2.2 (Use of Electronic 
Diaries), 8.2.6 (Blood Sampling 
Volumes, Table 4) 
Clarified requirements for Part A 
and Part B.  
Clarification of concomitant 
medication, eDiary, and blood 
sampling procedures during Part A 
and Part B.  
Section 8.2.2 (Use of Electronic 
Diaries), Appendix 1 (Schedule of 
Events, Table 17 footnote 7) 
Clarified that eDiary prompts to 
surveil for weekly COVID-19 
symptoms will be performed for 
all participants in Part A and 
Part B.  
Added eDiary prompt to solicit 
collection of participant history of 
facial injections or dermal fillers. 
Clarification. 
To assure all concomitant 
medications are recorded. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.2.4 (Physical Examination) 
Removed body mass index from 
the participant decision visit. 
Clarification. 
Section 8.2.6 (Blood Sampling 
Volumes) 
Updated maximum planned 
volume of blood collection for the 
complete study to include a range. 
Clarification. 
Section 8.3.2 (Medically Attended 
Adverse Events) 
Added suspected cases of 
anaphylaxis as an MAAE and 
requirement to report as an SAE.  
Sponsor collecting anaphylaxis 
information.  
Section 9.4 (Analysis Populations, 
Table 8); Synopsis 
Clarified Immunogenicity Subset. 
Clarification. 
Section 9.5.1.1 (Efficacy Analysis on 
Primary Endpoint), Appendix 4 
(Statistical Appendices, Table 23 and 
Table 24) 
Updated intercurrent events and 
estimands. 
Clarification of estimand. 
Section 9.5.1.3 (Long-term Efficacy 
Analysis); Synopsis 
Updated case count parameters. 
Provide long-term efficacy analysis 
strategy relevant to change in study 
design.  
Appendix 1 (Schedule of Events, 
Table 21 footnote 2, and Table 22 
footnote 2) 
Updated physical examination to 
symptom-directed physical 
examination and removed height 
and weight requirements from the 
Open-Label Clinic Visits. 
Clarification. 
 
Amendment 6, 23 Dec 2020 
Main Rationale for the Amendment: 
The purpose of this amendment is to inform all ongoing study participants of the availability of 
and eligibility criteria of any COVID-19 vaccine made available under an EUA and to offer 
participants who originally received placebo in this study the potential benefit of vaccination 
against COVID-19, given that the primary efficacy endpoint for mRNA-1273 against COVID-19 
was met per the protocol-defined IA.  
The summary of changes table provided here describes the major changes made in Amendment 6 
relative to Amendment 5, including the sections modified and the corresponding rationales. The 
synopsis of Amendment 6 has been modified to correspond to changes in the body of the protocol.  
Summary of Major Changes From Protocol Amendment 5 to Protocol Amendment 6:  

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Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and 
date. 
To reflect the new version and date 
of the protocol. 
Sections 1.1 (Synopsis), 1.2 (Schema), 
4.1.2 (Part B, the Open-Label 
Observational Phase), 6.2.8.1 
(Planned Unblinding), 7.3.1 
(Participant Withdrawal), and 11.1 
(Schedules of Events) 
Added a “Participant Decision 
clinic visit”. 
This visit provides the opportunity 
for study site personnel to discuss 
with and offer to participants, the 
choice to be unblinded, as well as 
offering to participants who 
originally received placebo, the 
choice to receive active vaccination 
with mRNA-1273 and possible 
vaccination against COVID-19. 
Participants will also sign a revised 
informed consent form at this visit. 
Sections 1.1 (Synopsis), 1.2 (Schema), 
4.1 (General Design), 4.2 (Scientific 
Rationale for Study), 6.2 (Method of 
Randomly Assigning Participants to 
Treatment Groups [Part A], Blinded 
Phase Only), and 11.1 (Schedules of 
Events) 
Changes to study design that split 
the study into a Blinded Phase 
and an Open-Label Observational 
Phase. 
These changes accommodate the 
breaking of the blind and offering of 
open-label vaccination to all 
participants. This change also 
distinguishes the Open-Label 
Supplemental Schedule of Events 
(Vaccination Phase) for participants 
who received placebo, and who 
meet EUA eligibility, and request to 
receive active vaccine. 
Sections 1.1 (Synopsis), 1.2 (Schema), 
4.1.2 (Part B, the Open-Label 
Observational Phase), and 11.1 
(Schedules of Events) 
Added a Supplemental SoE and a 
Modified Supplemental SoE. 
These provide paths for participants 
who choose to be unblinded and 
receive mRNA-1273, and for 
participants who previously 
received only 1 dose of blinded 
mRNA-1273 during the study 
(Blinded Phase), to transition into 
the Open-label Phase of the study. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 2.2.2 (Clinical Studies) 
Updated status of ongoing clinical 
studies, including this study 
(mRNA-1273-P301). 
The status of the 3 clinical studies 
(one Phase 1, one Phase 2a, and this 
Phase 3 study) have changed since 
Amendment 5. 
In addition, the results of the interim 
analyses in this study of the primary 
efficacy endpoint (prevention of 
COVID-19 infection), a major 
secondary endpoint (prevention of 
severe COVID-19), and safety and 
reactogenicity endpoints are now 
available and are provided here. 
These results provide the 
justification for offering participants 
the opportunity to receive active IP 
(mRNA-1273) and the potential 
benefit of vaccination against 
COVID-19. 
Section 1.1 (Synopsis) and 9.5.1.3 
(Long-term Efficacy Analysis) 
Addition of long-term efficacy 
analyses. 
Allows for the analysis of the 
long-term efficacy of mRNA-1273 
in the following treatment cohorts:  
• 
mRNA-1273 Cohort: 
Participants randomized to 
mRNA-1273 in the Blinded 
Phase. 
• 
Placebo Cohort: Participants 
randomized to Placebo in the 
Blinded Phase and did not 
crossover to mRNA-1273 in the 
Open-label Phase.  
• 
Placebo-mRNA-1273 Cohort: 
Participants randomized to 
Placebo in the Blinded Phase 
and crossed over to 
mRNA-1273 in the Open-label 
Phase. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 2.3.3 (Overall Benefit/Risk 
Conclusion) 
Updated the Benefit/Risk 
Assessment. 
Based on the interim results from 
this pivotal Phase 3 study, 
mRNA-1273 prevents COVID-19 
and severe COVID-19. The 
demonstrated clinical benefit of 
mRNA-1273 is supported by 
evidence of a robust immune 
response both in terms of binding 
antibodies (bAbs) and neutralizing 
antibodies (nAbs) as well as the 
induction of CD4+ T-cells with a 
Th-1 dominant phenotype. 
Section 11.1 
Added footnote to Table 16. 
To clarify that the eDiary Safety 
prompts will be triggering off on 
Day 61 to take into consideration 
the (-3 day) window allowance on 
Day 29. 
 
Amendment 5, 11 Nov 2020 
Main Rationale for the Amendment: 
The main purpose of this amendment is to clarify that the eDiary prompts for safety surveillance 
will be weekly and to add Month 19 safety call. 
The summary of changes table provided here describes the major changes made in Amendment 5 
relative to Amendment 4, including the sections modified and the corresponding rationales. The 
synopsis of Amendment 5 has been modified to correspond to changes in the body of the protocol. 
Summary of Major Changes From Protocol Amendment 4 to Protocol Amendment 5: 
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and 
date. 
To reflect the new version and date 
of the protocol. 
Section 11.1 
Updated Appendix 1 (Tables 16 
and 17) . 
To clarify the weekly schedule for 
eDiary prompts through Year 1 and 
Year 2 of follow-up. 
Section 11.1 
Added Month 19 Safety Call. 
To clarify that participants will have 
continuous weekly (eDiary 
prompts) and monthly (safety calls) 
through Year 1 and Year 2 of 
follow-up. 
 

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Amendment 4, 30 Sep 2020 
Main Rationale for the Amendment: 
The main purpose of this amendment is to increase the upper limit for stratification of enrolled 
participants considered “at risk” at Screening to 50%. 
The summary of changes table provided here describes the major changes made in Amendment 4 
relative to Amendment 3, including the sections modified and the corresponding rationales. The 
synopsis of Amendment 4 has been modified to correspond to changes in the body of the protocol. 
Summary of Major Changes From Protocol Amendment 3 to Protocol Amendment 4: 
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and 
date. 
To reflect the new version and date 
of the protocol. 
Section 6.2.1.1 (Stratification) 
Increased the upper limit for 
stratification of enrolled 
participants considered “at risk” 
at Screening to up to 50%, from 
40%.  
To enhance the diversity of the 
study population by increasing the 
number of racial and ethnic 
minority participants in the study. as 
participants from these communities 
often have higher rates of 
comorbidities. 
Section 9.5.1.1 (Efficacy Analysis on 
Primary Endpoint) and Section 11.4.1 
(Estimands and Estimand 
Specifications) 
Updated the description of an 
intercurrent event (unrelated 
death) and its strategy 
To align with the description in the 
Statistical Analysis Plan. 
 
Amendment 3, 20 Aug 2020 
Main Rationale for the Amendment: 
The main purpose of this amendment is to make changes to the protocol in response to feedback 
from Center for Biologics Evaluation and Research. 
The summary of changes table provided here describes the major changes made in Amendment 3 
relative to Amendment 2, including the sections modified and the corresponding rationales. Minor 
editorial or formatting changes are not included in this summary table. The synopsis of 
Amendment 3 has been modified to correspond to changes in the body of the protocol. 
Summary of Major Changes From Protocol Amendment 2 to Protocol Amendment 3: 
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and 
date. 
To reflect the new version and date 
of the protocol. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 5 (Study Population) 
Added a sentence to describe the 
intent to enroll a representative 
sample of racial and ethnic 
minority participants in the study.  
To enhance the diversity of the 
study population.  
Section 5.2 (Exclusion Criteria) 
Added clarification to exclusion 
criterion #11 to define the 
parameters based on screening 
CD4 count and viral load for 
exclusion of study participants. 
To clarify the definition of 
controlled HIV disease in the 
exclusion criterion such that only 
participants with well-controlled 
HIV disease are enrolled in the 
study. 
Section 5.2 (Exclusion Criteria) 
Removed “topical tacrolimus” 
from exclusion criterion #12. 
No evidence to support any 
systemic effect of topical tacrolimus 
to warrant excluding them. 
Section 6.2.1.1 (Stratification) 
Added HIV infection to the risk 
factors at Screening. 
To stratify participants based on 
certain risk factors.  
Section 8.2.3 (Demographics/Medical 
History) 
Added collection of risk factors 
for complications of COVID-19.  
To document the diagnosis of any 
risk factor for complications of 
COVID-19 used for stratification. 
Section 9.3 (Sample Size 
Determination) 
Removed redundant bullet.  
To remove redundancy in the 
assumptions listed. 
Section 9.5.2 (Safety Analyses) 
Removed safety analysis by 
serostatus. 
No added value for this analysis. 
Other subgroup analyses may be 
specified in the SAP, as needed. 
Section 9.5.5 (Subgroup Analyses) 
Removed the categories (white, 
non-white) from the Race 
Variable. 
To allow for more refined Race 
categorization being collected in the 
eCRF. 
Appendix 11.3 
Removed “cessation of 
exogenous hormonal therapy”. 
To allow postmenopausal women to 
take these medications if needed for 
the treatment of the symptoms of 
menopause. 
Appendix 11.3 
Removed “using hormonal 
contraception” from 
postmenopausal female with high 
FSH levels. 
Not a standard of care for women 
for treatment of menopausal 
symptoms. 
 
Amendment 2, 31 Jul 2020:  
Main Rationale for the Amendment: 
The main purpose of this amendment is to provide more intensive surveillance of symptoms and 
severity of cases of COVID-19 after the first dose of IP. 
The summary of changes table provided here describes the major changes made in Amendment 2 
relative to Amendment 1, including the sections modified and the corresponding rationales. Minor 
editorial or formatting changes are not included in this summary table. The synopsis of 
Amendment 2 has been modified to correspond to changes in the body of the protocol. 
Summary of Major Changes From Protocol Amendment 1 to Protocol Amendment 2: 

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Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Protocol Approval Page, 
Headers, Protocol Amendment 
Summary of Changes 
Updated the protocol version and date. 
Reflect the new version and 
date of the protocol. 
Section 4.1 (General Design), 
Section 7.2 (Discontinuation of 
Study Treatment), Section 8.1.1 
(Efficacy Assessments Related to 
COVID-19 and SARS-CoV-2 
Infection), Section 8.1.2 
(Surveillance for COVID-19 
Symptoms),Table 14 (Schedule of 
Events [Vaccination Phase, Day 1 
– Day 57]) 
Added a Day 29 NP swab prior to Dose 2. 
Improve surveillance for 
asymptomatic infection prior 
to Dose 2 to assist in 
discriminating COVID-19 
symptoms from solicited 
systemic reactions after 
vaccination. 
Section 4.1 (General Design), 
Table 15 (Schedule of Events 
[Surveillance Phase, Day 64 – 
Day 394]) 
Changed the clinic visit at Month 4 to a 
safety call. 
Improve participant safety and 
adherence to protocol. 
Section 4.1 (General Design), 
Section 8.1.2 (Surveillance for 
COVID-19 Symptoms), Table 14 
Footnote 5 (Schedule of Events 
[Vaccination Phase, Day 1 
– Day 57]) 
Clarified symptom duration (> 48 hours) 
to trigger NP swab collection and 
investigator judgement whether to obtain 
an NP swab in the 7 days following 
vaccination due to overlap of solicited 
systemic symptoms and COVID-19. 
Improve surveillance for cases 
of COVID-19. 
Section 4.1 (General Design), 
Section 8.1.3 (Convalescent Period 
Starting with the Illness Visit), 
Section 8.1.4 (Ancillary Supplies 
for Participant Use) 
Removed mention of continuous 
biometric monitoring. 
Simplify data management 
and clinical operations. 
Section 5.1 (Inclusion Criteria), 
Section  
Removed the inclusion criterion regarding 
male contraception. 
Requirement not generally 
applicable for a Phase 3 
vaccine study. 
Section 5.2 (Exclusion Criteria), 
Section 6.4.3 (Concomitant 
Medications and Vaccines that May 
Lead to the Elimination of a 
Participant from Per-Protocol 
Analyses) 
Clarified language around influenza 
vaccination. 
Make restrictions on influenza 
vaccination less restrictive 
than for other licensed 
vaccines relative to 
administration of 
investigational product. 
Section 5.2 (Exclusion Criteria) 
Removed restriction on enrollment of 
participants with human 
immunodeficiency virus (HIV) infection. 
Participants on stable 
antiretroviral therapy are not 
excluded, which diversifies 
the participant group. 
Section 8.3.7 (Time Period and 
Frequency for Collecting AE and 
SAE Information), Section 8.3.10 
(Reporting Adverse Events) 
Added expedited reporting of confirmed 
COVID-19 cases. 
Improve surveillance for cases 
of COVID-19 
Section 8.4.2 (Data and Safety 
Monitoring Board) 
Added an Oversight Group. 
Clarify responsibility for 
declaring early efficacy or for 
taking action to stop, pause, or 
continue the study. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.4.2 (Data and Safety 
Monitoring Board) 
Updated description of monitoring for 
potential harm, including details on case 
counting for the purpose of harm 
monitoring to align with a DSMB 
analysis plan. 
Clarify description for harm 
monitoring, based on FDA 
feedback. 
Amendment 1, 26 Jun 2020: 
Main Rationale for the Amendment: 
The main purpose of this amendment is to provide more intensive surveillance of symptoms and 
severity of cases of COVID-19 after the first dose of IP. 
The summary of changes table provided here describes the major changes made in Amendment 1 
relative to the original protocol, including the sections modified and the corresponding rationales. 
Minor editorial or formatting changes are not included in this summary table. 
Summary of Major Changes in Protocol Amendment 1: 
Section # and Name 
Description of Change 
Brief Rationale 
Title page, Signature page, 
and header 
Updated the protocol version and date. 
Reflect the new version and date 
of the protocol. 
Synopsis; Section 4.1, General 
Design; Section 8.1.3, 
Convalescent Period; Section 
11.1, schedules of events, 
Table 17 
Increased the frequency of telemedicine 
contacts during the Convalescent Period 
following the Initial Illness Visit. 
Improve the amount and quality 
of COVID-19 symptom data 
collected during the 
Convalescent Period. 
Synopsis; Section 4.1, General 
Design; Section 8.1.3, 
Convalescent Period; 
Section 8.1.4, Ancillary 
Supplies for Participant Use; 
Section 11.1, schedules of 
events, Table 17 
Added monitoring of oxygen saturation to 
the Convalescent Period.  
Improve surveillance for 
incidence of COVID-19 during 
the study. 
Synopsis; Section 8.1.3, 
Convalescent Period; 
Section 8.1.4, Ancillary 
Supplies for Participant Use; 
Section 11.1, schedules of 
events, Table 17 
Increased the frequency of monitoring for 
SARS-CoV-2, using saliva as the preferred 
sample matrix after the Illness Visit during 
the Convalescent Period. 
Improve the sensitivity of 
monitoring the time course of 
viral shedding during 
COVID-19. 
Synopsis; Section 3, 
Objectives and Endpoints 
Added a respiratory sample for hospitalized 
participants as a matrix for confirming the 
presence of SARS-CoV-2. 
Increase the potential number of 
evaluable COVID-19 cases. 
Synopsis; Section 3, 
Objectives and Endpoints 
Broadened the definition for seroconversion 
at a participant level.  
Included neutralizing antibody 
(nAb) in addition to binding 
antibody (bAb). 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8, Study Assessments 
and Procedures; Section 8.1.3, 
Convalescent Period; 
Section 8.1.4, Ancillary 
Supplies for Participant Use; 
Section 8.2.2, Use of 
Electronic Diaries; 
Section 11.1, schedules of 
events, Table 17 
Eliminated paper diaries, substituting an 
instruction card listing symptoms and a 
severity grading system to enhance the 
quality of data obtained by telemedicine 
contacts. 
Reduce fomite transmission of 
SARS-CoV-2 and increase 
frequency of investigative staff 
interactions with participants 
during the Convalescent Period.  
Section 8.1.2, Surveillance for 
COVID-19 Symptoms 
Decreased the number of symptoms (to one 
of the 11 CDC symptoms) that would result 
in an Illness Visit. 
Increase the likelihood of 
capturing all COVID-19 cases in 
the earliest stage of disease. 
Section 8.2.2, Use of 
Electronic Diaries  
Expanded the scope of eDiary prompts and 
data collected during the Surveillance Phase.  
Increase the likelihood of 
capturing all COVID-19 cases in 
the earliest stage of disease. 
 

Signature Page for VV-CLIN-003185 v4.0
Signature Page for VV-CLIN-003185 v4.0
Approval
12-Apr-2022 01:48:09 GMT+0000
PPD