A Phase 2A, Randomized, Stratified, Observer-Blind Study to Evaluate the Immunogenicity and Safety of mRNA-1283 Vaccine Boosters for SARS-CoV-2
Phase: PHASE2
Conditions: SARS-CoV-2
Sponsor: ModernaTX, Inc.

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
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CLINICAL STUDY PROTOCOL 
Protocol Title: 
A Phase 2a, randomized, stratified, observer-blind study 
to evaluate the immunogenicity and safety of mRNA-
1283 vaccine boosters for SARS-CoV-2 
Protocol Number: 
mRNA-1283-P201 
Sponsor Name: 
ModernaTX, Inc. 
Legal Registered Address: 
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: 
IND: 027196 
Amendment 2 Date 
31 Jan 2022 
Amendment 1 Date 
22 Oct 2021 
Original Protocol Date: 
01 Sep 2021 
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) of Technical Requirements for Registration of 
Pharmaceuticals for Human Use, E6(R2) Good Clinical Practice (GCP) Guidance. 
PPD
PPD
PPD

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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PROTOCOL APPROVAL – SPONSOR SIGNATORY 
Study Title: 
A Phase 2a, randomized, stratified, observer-blind study to evaluate 
the immunogenicity and safety of mRNA-1283 vaccine boosters for 
SARS-CoV-2 
Protocol Number: 
mRNA-1283-P201 
Amendment Number 
2 
Amendment Date: 
31 Jan 2022 
 
Protocol accepted and approved by: 
 
 
 
 
 
 
 
ModernaTX, Inc.  
200 Technology Square  
Cambridge, MA 02139  
Telephone: 
 
 
Date 
 
 
 
PPD
PPD

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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DECLARATION OF INVESTIGATOR 
I have read and understood all sections of the protocol entitled “A Phase 2a, randomized, 
stratified, observer-blind study to evaluate the immunogenicity and safety of mRNA-1283 
vaccine boosters for SARS-CoV-2” and the most recent version of the Investigator’s Brochure 
(IB). 
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) of 
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) 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. 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. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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PROTOCOL AMENDMENT SUMMARY OF CHANGES 
DOCUMENT HISTORY 
Document 
Date 
Amendment 2 
31 Jan 2022 
Amendment 1 
22 Oct 2021 
Original Protocol 
01 Sep 2021 
Amendment 2, 31 Jan 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 
The main rational for this amendment is to add an open label study part (Part B) to evaluate the 
safety, reactogenicity, and immunogenicity of mRNA-1283.529 booster vaccine - an 
omicron-specific booster vaccine candidate. 
The summary of changes table provided here describes the changes made in Amendment 2 
relative to Amendment 1, including the sections modified and the corresponding rationale. The 
synopsis of Amendment 2 has been modified to correspond to changes in the body of the 
protocol. Minor editorial and grammatical corrections were also made. 
Summary of Major Changes from Original Protocol to Protocol Amendment 1: 
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Signature Page, 
Protocol Amendment Summary of 
Changes, and Header  
• 
Updated the protocol version 
and date.  
• 
Added Protocol Amendment 
Summary of Changes for 
Amendment 1.  
Updated to reflect the new 
version and date.  
Throughout the protocol 
• 
Addition of Study Part B to 
add mRNA-1283.529 
booster doses to the protocol 
• 
Added language for Study 
Part A, designating the 6 
treatment arms described in 
the original protocol as Part 
A 
Updated to evaluate the 
safety, reactogenicity, and 
immunogenicity of the 
mRNA-1283.529 vaccine 
candidate at two dose levels 
Section 1.2.3 (mRNA-1273.529) 
• 
Section added with 
description of the mRNA-
1273.529 vaccine candidate 
Added to provide a description 
of the new vaccine candidate 
for Part B 
Protocol Synopsis, Section 2 
(Objectives and Endpoints) 
• 
Addition of objectives and 
endpoints for Part B  
Added to provide the 
descriptions of the objectives 
and endpoints of the new part 
of the study. 

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31 Jan 2022 
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Section # and Name 
Description of Change 
Brief Rationale 
Protocol Synopsis, Section 4 
(Study Population), Section 8.3 
(Sample Size Determination) 
• 
Changed Part A participant 
number from “approximately 
420” to “up to 420.” 
Change reflects Part A and 
Part B targeted enrollment. 
Protocol Synopsis, Section 4.1 
(Inclusion Criteria) 
1. Added language to inclusion 
criterion 6 to specify that 
mRNA-1273 refers 
specifically to the primary 
vaccine series 
Updated for clarity. 
Protocol Synopsis, Section 8.5.1 
(Baseline Characteristics and 
Demographics), Section 8.5.2 
(Efficacy Analysis), Section 8.5.3 
(Safety Analyses), 8.5.4.1 
(Analysis for the Primary 
Immunogenicity Objective), 
Section 8.5.4.2 (Analysis for the 
Secondary and Exploratory 
Immunogenicity Objectives), 
Section 8.5.5 (Subgroup 
Analyses) 
2. Addition of references to 
Part A and Part B and 
statistical analyses and 
considerations for Part B 
Updated to differentiate 
between Part A and B and to 
add the statistical analyses 
specific to Part B 
Section 8.6.2 (Interim Analysis) 
3. Section added to describe the 
conditions for the Part B 
interim analysis and the 
groups involved in the 
analysis 
Added to allow for an interim 
analysis based on Part B of 
the study.  
Section 10.1 Appendix 1: 
Schedule of Events 
4. Added a Day 90 visit  
Added to allow for a blood 
draw for humoral 
immunogenicity testing and a 
nasopharyngeal swab for 
COVID-19 testing. 
 

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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PROTOCOL SYNOPSIS 
Name of Sponsor/Company: ModernaTX, Inc. 
Name of Investigational Product: mRNA-1283 and mRNA-1283.211 vaccine candidates 
Name of Active Ingredient: Part A - mRNA-1283 and mRNA-1283.211, respectively; Part B 
– mRNA-1283.529 
Protocol Title: A Phase 2a, randomized, stratified, observer-blind study to evaluate the 
immunogenicity and safety of mRNA-1283 vaccine boosters for SARS-CoV-2 
Protocol Number: mRNA-1283-P201 
Study Period (months): Approximately 13 months 
Phase of Development: Phase 2a 
Estimated Date First Participant Enrolled: 29-Nov-2021 
Estimated Date Last Participant Completed: 29-Nov-2022 
Total Number of Sites: Up to 13 sites in the United States or its territories 

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Objectives and Endpoints: 
The objectives that will be evaluated in this study and the endpoints and time points associated 
with each objective are provided in the table below: 
Part A Objectives and Endpoints 
Objectives 
Endpoints 
Primary 
 
• 
To assess the safety and 
reactogenicity of the study 
vaccines 
• 
Frequency and grade of each solicited local and 
systemic reactogenicity adverse reaction (AR) during a 
7-day follow-up period after vaccination 
• 
Frequency and severity of any unsolicited adverse 
events (AEs) during the 28-day follow-up period after 
vaccination 
• 
Frequency of any serious AEs (SAEs), medically 
attended AEs (MAAEs), AEs leading to withdrawal 
from study participation, and AEs of special interest 
(AESIs) from Day 1 to end of study (EoS) 
• 
To assess the immunogenicity 
of the study vaccines 
• 
Immune response of the study vaccine candidates 
against the ancestral severe acute respiratory syndrome 
coronavirus 2 (SARS-CoV-2) and against 
SARS-CoV-2 variants, including B.1.351, at Day 29 
by geometric mean titer (GMT), geometric mean fold 
rise (GMFR), and seroresponse rate (SRR) 
• 
To compare the immune response elicited by the 
mRNA-1283 study vaccine candidates with the 
immune response elicited by the mRNA-1273 vaccine 
when administered as a booster, at Day 29 by GMT, 
GMFR, and SRR 
Secondary 
 
• 
To evaluate the 
immunogenicity at all 
immunogenicity time points 
• 
Immune response of the study vaccine candidates 
against the ancestral SARS-CoV-2 and against 
SARS-CoV-2 variants at all immunogenicity time 
points by GMT, GMFR, and SRR 
Exploratory 
 
• 
To characterize cellular 
immunogenicity 
• 
Frequency, magnitude, and phenotype of 
antigen-specific B- and T-cells, to include B-cell and 
T-cell receptor repertoires 

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
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• 
To conduct active detection of 
symptomatic and asymptomatic 
SARS-CoV-2 infection 
• 
Laboratory-confirmed asymptomatic or symptomatic 
SARS-CoV-2 infection will be defined in participants: 
− 
Negative SARS-CoV-2 anti-nucleocapsid antibody 
blood test at Day 1 that becomes positive at Day 29 
or later, OR 
− 
Positive SARS-CoV-2 reverse transcriptase 
polymerase chain reaction (RT-PCR) from 
nasopharyngeal swab 
• 
To assess the genetic and/or 
phenotypic relationships of 
isolated SARS-CoV-2 strains 
to the vaccine sequence 
• 
Comparison of the SARS-CoV-2 genetic sequence of 
viral isolates with the vaccine sequence and 
characterization of immune responses to vaccine 
breakthrough isolates 
 
Part B Objectives and Endpoints 
Objectives 
Endpoints 
Primary 
 
• 
To assess the safety and 
reactogenicity of the mRNA-
1283.529 booster vaccine 
candidate 
• 
Frequency and grade of each solicited local and 
systemic reactogenicity AR during a 7-day follow-up 
period after vaccination 
• 
Frequency and severity of any unsolicited adverse AEs 
during the 28-day follow-up period after vaccination 
• 
Frequency of any SAEs, MAAEs, AEs leading to 
withdrawal from study participation, and AEs of 
special interest (AESIs) from Day 1 to EoS 
• 
To assess the immunogenicity 
of the mRNA-1283.529 booster 
vaccine candidate as the second 
booster dose 
• 
Immune response of the 1283.529 booster vaccine 
candidate against SARS CoV 2 Omicron variant 
(B.1.1.529), at Day 29 by geometric mean titer (GMT), 
geometric mean fold rise (GMFR), and seroresponse 
rate (SRR) 
Secondary 
 
• 
To assess the immunogenicity 
at all immunogenicity time 
points 
• 
Immune response of the mRNA-1283.529 vaccine 
candidate against the ancestral SARS-CoV-2 and 
against SARS-CoV-2 variants at all 
immunogenicity time points by GMT, GMFR, and 
SRR 
Exploratory 
 
• 
To characterize cellular 
immunogenicity 
• 
Frequency, magnitude, and phenotype of 
antigen-specific B- and T-cells, to include B-cell and 
T-cell receptor repertoires 
• 
To conduct active detection of 
symptomatic and asymptomatic 
SARS-CoV-2 infection 
• 
Laboratory-confirmed asymptomatic or symptomatic 
SARS-CoV-2 infection will be defined in participants: 

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
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− 
Negative SARS-CoV-2 anti-nucleocapsid antibody 
blood test at Day 1 that becomes positive at Day 29 
or later, OR 
− 
Positive SARS-CoV-2 RT-PCR from 
nasopharyngeal swab 
• 
To evaluate the genetic and/or 
phenotypic relationships of 
isolated SARS-CoV-2 strains 
to the vaccine sequence 
• 
Comparison of the SARS-CoV-2 genetic sequence of 
viral isolates with the vaccine sequence and 
characterization of immune responses to vaccine 
breakthrough isolates 

ModernaTX, Inc. 
31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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Overall Study Design: 
This is a Phase 2a study that consists two parts: Part A is an observer-blind, stratified, 
randomized design to evaluate the immunogenicity, safety, and reactogenicity of mRNA-1283, 
mRNA-1283.211, and potentially of other study vaccine candidates, administered as a single 
booster dose to participants 18 years and older who were previously vaccinated with 
mRNA-1273. Part B is an open-label design to evaluate the immunogenicity, safety, and 
reactogenicity of mRNA-1283.529 administered as a single booster dose to participants 18 
years and older who were previously vaccinated with mRNA-1273. 
Part A of this study will assess whether a single dose of mRNA-1283 at three different dose 
levels 
 or mRNA-1283.211 at two different dose levels 
 will 
boost antibody responses to the Wuhan-Hu-1 (ancestral strain of the severe acute respiratory 
syndrome coronavirus 2 [SARS-CoV-2]) virus, and to the B.1.351 variant, and potentially 
other SARS-CoV-2 variants, and inform dose selection for mRNA-1283 booster vaccines for 
subsequent clinical evaluation. The study will include an active comparator group of 
participants who will receive mRNA-1273 
. 
Participants in Part A who received the primary series of mRNA-1273 
 with 
appropriate documentation at least 6 months prior will be randomized 1:1:1:1:1:1 to receive a 
single boost of mRNA-1283 at one of three dose levels, a single boost of mRNA-1283.211 at 
one of two dose levels, or a single dose of the active comparator, mRNA-1273. 
Part A Treatment Groups: 
Treatment Group 
Vaccine 
Dose Level1 
N 
1 
mRNA-1283 
70 
2 
70 
3 
70 
4 
mRNA-1283.211 
70 
5 
70 
6 
mRNA-1273 
70 
1 Dose levels for mRNA-1283.211 and mRNA-1273 are total mRNA in 1:1 ratio of mRNA-1283 and mRNA-1283.351 or 
mRNA-1273 and mRNA-1283.351, respectively. 
Part B of this study will assess whether a single dose of mRNA-1283.529 at two different dose 
levels 
 as the second booster after a first booster of mRNA-1273 
, at least 3 
months prior, will boost antibody response to the ancestral strain of the SARS-CoV-2, the 
B1.1.529 variant, and potentially other SARS-CoV-2 variants, and inform dose selection for 
mRNA-1283.529 booster vaccine candidate for subsequent clinical evaluation. 
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31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
mRNA-1283 
 
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Participants in Part B who received the primary series of mRNA-1273 
 and a first 
booster of mRNA-1273 
 at least 3 months prior will be enrolled in a 1:1 ratio to receive 
a single boost of mRNA-1283.529 as the second booster dose at one of two dose levels 
Part B Treatment Groups:  
Treatment Group 
Vaccine 
Dose Level 
N 
1 
mRNA-1283.529 
 
70 
2 
 
70 
Enrollment in both parts of this study will be stratified by age with two age strata: 18-55 years 
of age and ≥ 56 years of age, with at least 20% but no more than 50% of participants 56 years 
of age or older. Those with documented prior SARS-CoV-2 infection are eligible to participate 
if also previously vaccinated with mRNA-1273. Prior infection status will be confirmed by 
anti-nucleocapsid antibody testing of all participants. 
Participants in both parts will have up to 6 study visits; 5 visits if screening and randomization 
are performed on the same day. Study vaccine will be administered as a single dose on Day 1. 
Additional safety and immunogenicity study visits will occur on Days 8 (safety call only), 15, 
29, 181, and 366 (end of study [EoS]). Study visits will include scheduled safety phone calls 
every 2 weeks to collect MAAEs, AESIs, AEs leading to withdrawal, SAEs, and information 
about concomitant medications associated with these events, as well as to collect information 
about receipt of nonstudy vaccinations temporally associated with these events. 
At the vaccination visit (Day 1), participants will be instructed how to document and report 
solicited ARs in a provided electronic diary. Solicited ARs will be assessed for 7 days after the 
injection (the day of injection and the following 6 days), and unsolicited AEs will be assessed 
for 28 days after each injection. Medically attended AEs, SAEs, AESIs, and AEs leading to 
withdrawal will be assessed throughout the study. All participants will be tested for the 
presence of SARS-CoV-2 anti-nucleocapsid antibodies at Days 1, 29, 181, and 366, as well as 
by nasopharyngeal swab RT-PCR on Days 1, 29, 181, and 366. Active surveillance for 
intercurrent or breakthrough SARS-CoV-2 infection will occur throughout the study and be 
reported as AEs (confirmed symptomatic infections will be reported as MAAEs if not an 
SAE). Symptomatic infection will be prompted by signs and symptoms meeting the US 
Centers for Disease Control and Prevention (CDC) case definition for coronavirus disease 
2019 (COVID-19), as well as the clinical suspicion of the site investigator. Participants will be 
asked to contact the study site to arrange for a prompt, thorough, and careful assessment. 
Participants will have blood sampled at scheduled study site visits (Days 1, 15, 29, 181, and 
366) during the study for immunogenicity assessments or other medical concerns according to 
the investigator’s judgment. 
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31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
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Participants may experience AEs, including symptoms of COVID-19, 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 should be completed for each unscheduled visit. 
In addition, participants may have blood sampled at unscheduled visits for acute respiratory 
symptoms. 
Safety Oversight: Blinded safety monitoring for this study will include study team members, 
inclusive of, at a minimum, the Sponsor medical monitor, Sponsor safety physician (from 
Pharmacovigilance), and contract research organization medical monitor. The study team will 
conduct ongoing safety reviews during the study and will be responsible for monitoring of 
safety concerns during the study, as described in the Safety Management Plan. 
An independent Data Safety Monitoring Board, composed of external and independent subject 
matter experts and an unblinded statistician, will conduct unblinded reviews of safety data on 
an ad hoc basis as requested by the study team members. 
An independent Cardiac Event Adjudication Committee that includes pediatric and adult 
cardiologists will review any suspect cases of myocarditis and pericarditis to determine if they 
meet CDC criteria of “probable” or “confirmed” events, and to assess severity. 
Study Duration: Approximately 13 months for each participant. 
Number of Participants: In Part A up to 420 participants previously vaccinated for 
COVID-19 with mRNA-1273 will receive a single boost of mRNA-1283 at one of three dose 
levels, a single boost of mRNA-1283.211 at one of two dose levels, or a single dose of the 
active comparator, mRNA-1273, in a 1:1:1:1:1:1 ratio, ie, up to 70 participants per treatment 
group. In Part B, up to 140 participants previously vaccinated with mRNA-1273 primary 
series and who also received an mRNA-1273 booster dose at least 3 months prior will receive 
a single boost of mRNA-1283.529 as the second booster dose at one of two dose levels in a 
1:1 ratio, ie, up to 70 participants per dose level. 

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31 Jan 2022 
Protocol: mRNA-1283-P201 Amendment 2 
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Study Eligibility Criteria:  
Inclusion Criteria: 
Each participant must meet all of the following criteria to be enrolled in this study: 
1. At least 18 years of age at the time of consent (Screening Visit). 
2. Investigator assessment that participant understands and is willing and physically able 
to comply with protocol-mandated follow-up, including all procedures. 
3. Participant has provided written informed consent for participation in this study, 
including all evaluations and procedures as specified in this protocol. 
4. Female participants of nonchildbearing potential may be enrolled in the study. 
Nonchildbearing potential is defined as bilateral tubal ligation > 1 year prior to 
screening, bilateral oophorectomy, hysterectomy, or menopause. Follicle-stimulating 
hormone level may be measured at the discretion of the investigator to confirm 
postmenopausal status. 
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 on the day of vaccination (Day 1). 
• Has practiced adequate contraception or has abstained from all activities that could 
result in pregnancy for at least 28 days prior to Day 1. 
• Has agreed to continue adequate contraception through 3 months following the last 
vaccine administration. 
• Is not currently breastfeeding. 
• Adequate female contraception is defined as consistent and correct use of a US 
Food and Drug Administration–approved contraceptive method in accordance with 
the product label. 
6. Participant must have received their second dose of the mRNA-1273 primary series at 
least 6 months prior to screening and enrollment (Part A) or have received the mRNA-
1273 series and an mRNA-1273 booster dose (50 ug) at least 3 months prior to 
screening and enrollment (Part B). 
Exclusion Criteria: 
Participants meeting any of the following criteria will be excluded from the study: 

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1. Had significant exposure to someone with SARS-CoV-2 infection or COVID-19 in the 
past 14 days, defined by the CDC as a close contact of someone who has COVID-19. 
2. Is acutely ill or febrile (temperature ≥ 38.0°C/100.4°F) less than 72 hours prior to or at 
the Screening Visit or Day 1. Participants meeting this criterion may be rescheduled 
and will retain their initially assigned participant number. 
3. Currently has symptomatic acute or unstable chronic disease requiring medical or 
surgical care, to include significant change in therapy or hospitalization for worsening 
disease, at the discretion of the investigator. 
4. Has a medical, psychiatric, or occupational condition that may pose additional risk as a 
result of participation, or that could interfere with safety assessments or interpretation 
of results according to the investigator’s judgment. 
5. History of myocarditis, pericarditis, or myopericarditis within 2 months prior to 
Screening. Participants who have not returned to baseline after their convalescent 
period will also be excluded. 
6. Has a current or previous diagnosis of immunocompromising condition to include 
human immunodeficiency virus, immune-mediated disease requiring 
immunosuppressive treatment, or other immunosuppressive condition. 
7. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days 
in total within 6 months prior to screening (for corticosteroids ≥ 10 mg/day of 
prednisone equivalent) or is anticipating the need for immunosuppressive treatment at 
any time during participation in the study. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the injection 
(Day 1) or plans to receive a licensed vaccine within 28 days before or after the study 
injection, with the exception of influenza vaccines, which may be given 14 days before 
or after receipt of a study vaccine. 
9. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive these during the study. 
10. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
11. Plans to participate in an interventional clinical trial of an investigational vaccine or 
drug while participating in this study. 
12. Is an immediate family member or household member of study personnel, study site 
staff, or Sponsor personnel. 

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Study Treatments:  
Investigational Product, Dosage, and Mode of Administration: 
The term “investigational product (IP)” refers to the mRNA-1283, mRNA-1283.211, mRNA-
1283.529, and mRNA-1273 vaccines administered in this study. 
The mRNA-1283 Drug Product is a lipid nanoparticle (LNP) dispersion containing a single 
messenger ribonucleic acid (mRNA) sequence that encodes a protein made up of 2 segments 
of the SARS-CoV-2 spike (S) protein: the N-terminal domain (NTD) and receptor-binding 
domain (RBD), which are linked together with a 7-amino-acid flexible linker. These three 
proteins (NTD, RBD, and linker) are attached to a 23-amino-acid transmembrane domain from 
influenza hemagglutinin (HATM) via a 5-amino-acid flexible linker. This entire protein makes 
up the NTD-RBD-HATM antigen and is encoded by mRNA-1283. The mRNA is combined in 
a mixture of 4 lipids common to the Sponsor’s mRNA vaccine platform: 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 
(PEG-2000-DMG). 
mRNA-1283 is provided as a sterile liquid for injection, as a white to off-white dispersion in 
appearance, at a concentration of 0.4 mg/mL in 20 mM Tris buffer containing 87 mg/mL 
sucrose and 10.7 mM sodium acetate, at pH 7.5. mRNA-1283 is packaged in 2R US 
Pharmacopeia (USP) Type I borosilicate glass vials with a PLASCAP® vial seal containing a 
13-mm FluroTec-coated plug stopper and has a 0.6-mL nominal fill volume. 
mRNA-1273 is an LNP dispersion of an mRNA encoding the full-length prefusion stabilized 
S protein of SARS-CoV-2 formulated in LNPs as described for mRNA-1283. mRNA-1273 
injection is provided as a sterile liquid for injection, 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 4.3 mM sodium acetate, at pH 7.5. 
Each dose of IP will be prepared for each participant based on the treatment group. Each 
injection will have a volume of 0.25 mL. The vaccines will contain mRNA-1283 at the doses 
of 
, mRNA-1283.211 at the doses of 
, mRNA-1273 at the dose of 
, and mRNA-1283.529 at the doses of 
. Vaccine preparation instructions are 
detailed in the mRNA-1283-P201 Pharmacy Manual. 
Investigational product will be administered as an IM injection into the deltoid muscle on 
Day 1 according to the procedures specified in the Pharmacy Manual. Preferably, vaccine 
should be administered into the nondominant arm. Participants will be monitored for a 
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31 Jan 2022 
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minimum of 30 minutes after vaccination. Assessments will include vital sign measurements 
and monitoring for local or systemic ARs. 
Procedures and Assessments: 
Safety Assessments: 
Safety assessments will include monitoring and recording of the following for each 
participant, according to the schedule of events (SoE): 
• Solicited local and systemic ARs that occur during the 7 days following 
vaccination (ie, the day of injection and 6 subsequent days). Solicited ARs will be 
recorded daily using eDiaries. 
• Unsolicited AEs observed or reported during the 28 days following vaccination 
(ie, the day of injection and 27 subsequent days). 
• MAAEs from vaccination on Day 1 through EoS or withdrawal from the study. 
• AESIs from vaccination on Day 1 through EoS or withdrawal from the study. 
• AEs leading to study participation withdrawal from Day 1 through EoS or 
withdrawal from the study. 
• SAEs from vaccination on Day 1 through EoS or withdrawal from the study. 
• Vital sign measurements before and after vaccine administration 
• Physical examination findings (if performed) 
• Details of all pregnancies in female participants will be collected after the start of 
study treatment and until the end of their participation in the study. 
The incidence and severity of the above events will be monitored by the blinded study team 
members. 
Immunogenicity Assessments: 
Blood samples for immunogenicity assessments will be collected at the time points indicated 
in the SoE. The following immunogenicity assessments will be measured: 
• Serum binding antibody (bAb) level against SARS-CoV-2, as measured by 
ligand-binding assay specific to the SARS-CoV-2 S protein and the S protein RBD. 
• Serum neutralizing antibody (nAb) level against SARS-CoV-2, as measured by 
pseudovirus neutralization assays. 

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• The above assays will include SARS-CoV-2 variant antigens, pseudotyped virus 
expressing SARS-CoV-2 S protein, or virus isolates to assess differences in 
immunologic responses to different SARS-CoV-2 variant S proteins. 
• Testing for serologic markers for SARS-CoV-2 infection, as measured by 
anti-nucleocapsid antibodies detected by immunoassay at study enrollment (Day 1) 
and scheduled post-baseline time points. 
Vaccine efficacy will not be formally assessed in this study, but active surveillance for 
COVID-19 and SARS-CoV-2 infection through monthly contact and scheduled blood 
collection will be performed. 

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Statistical Methods: 
No formal hypotheses will be tested. 
Sample Size Determination: 
The sample size for this trial is not driven by statistical assumptions for formal hypothesis 
testing. The number of proposed participants is considered sufficient to provide a descriptive 
summary of the safety and immunogenicity of each treatment group. In Part A, up to 
420 participants will be randomized to 6 treatment arms in a 1:1:1:1:1:1 ratio to mRNA-1283 
at three dose levels, mRNA-1283.211 at two dose levels, and mRNA-1273 at a single dose 
level, respectively (ie, up to 70 participants for each treatment group). In Part B, up to 140 
participants will be enrolled in two treatment arms of mRNA-1283.529 in a 1:1 ratio. 
Enrollment in both parts of this study will be stratified by age with two age strata: 18-55 years 
of age and ≥ 56 years of age, with at least 20% but not more than 50% of participants 56 years 
of age or older. 
Analysis Sets: 
Analysis sets are described below (same definition across part A and B if applicable) 
Set 
Description 
Randomization Analysis 
Set (Part A) 
The Randomization Analysis Set consists of all participants who 
are randomized. Randomization Analysis Set is applicable to 
Part A only. 
Full Analysis Set (FAS) 
The FAS consists of all randomized/enrolled (Part A: 
randomized, Part B: enrolled) participants who receive one dose 
of IP. 
Per-Protocol (PP) Set for 
Immunogenicity 
The PP Set for Immunogenicity consists of all participants in the 
FAS who receive the planned dose of IP and who have no major 
protocol deviations that impact key or critical data. 
The PP Set for Immunogenicity will be used as the primary 
analysis set for analyses of immunogenicity unless otherwise 
specified. 
Safety Set 
The Safety Set consists of all randomized/enrolled (Part A: 
randomized, Part B: enrolled) participants who receive 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. 
Solicited Safety Set 
The Solicited Safety Set consists of all participants in the Safety 
Set who contribute any solicited AR data. 
The Solicited Safety Set will be used for the analyses of 
solicited ARs. Participants will be included in the treatment 
group corresponding to the IP that they actually received. 

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Safety Analyses: 
Part A and B: 
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. Participants will be included in the treatment group corresponding to the IP that they 
actually received. 
Safety and reactogenicity will be assessed by clinical review of all relevant parameters, 
including solicited ARs (local and systemic ARs), unsolicited AEs, treatment-related AEs, 
severe AEs, SAEs, MAAEs, AESIs, and AEs leading to withdrawal from study participation. 
The number and percentage of participants with any solicited local AR, with any solicited 
systemic AR, with any solicited AR during the 7-day follow-up period after the single dose, 
and with Grade 3 or higher solicited AR will be provided. A 2-sided 95% exact CI using the 
Clopper-Pearson method will also be provided for the percentage of participants with any 
solicited AR for each treatment group. 
The number and percentage of participants with unsolicited AEs, treatment-related AEs, 
severe AEs, SAEs, MAAEs, AESIs, and AEs leading to withdrawal from study participation 
will be summarized. Unsolicited AEs will be presented by Medical Dictionary for Regulatory 
Activities (MedDRA) system organ class and preferred term. Unsolicited AEs will be coded 
according to the MedDRA Dictionary for Adverse Reaction Terminology. 
The number of events of solicited ARs, unsolicited AEs, SAEs, MAAEs, AEs leading to 
withdrawal, and AESIs will be reported in summary tables accordingly. Vital signs and 
physical examination findings will be summarized. Pregnancy outcomes will also be 
summarized. 
Immunogenicity Analyses: 
Immunogenicity analyses will be performed based on the PP Set for Immunogenicity and 
provided by treatment group. 
Analysis for the Primary Immunogenicity Objective: 
Part A: 
For the primary immunogenicity endpoints of levels of SARS-CoV-2–specific nAb and 
SARS-CoV-2–specific bAb against the SARS-CoV-2 prototype virus strain and against the 
variant strains including B.1.351, immune response of each treatment group will be assessed 
with respect to the mRNA-1273 
 booster dose. An analysis of covariance (ANCOVA) 
model will be employed to compare immune response between each treatment group against 
CCI

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the mRNA-1273 
 booster dose. Day 29 antibody titers (against prototype virus strain or 
the variant strain) will be included in the model as a dependent variable and treatment group 
variable (mRNA-1283 at each dose level, mRNA-1283.211 at each dose level, and 
mRNA-1273 
) will be included as fixed effect. The model will also adjust for age group 
(< 56, ≥ 56). The GMT will be estimated by the geometric least square mean (GLSM) from 
the model for each group and corresponding 95% CI will be provided. The ratio of GMTs for 
each treatment group with respect to mRNA-1273 
 booster dose will be estimated by the 
ratio of GLSM from the model. The 95% CI for the ratio of GLSM will be provided to assess 
the between-groups difference (each treatment group against mRNA-1273 
 booster dose) 
in immune response against the prototype strain (or B.1.351 variant strain). 
The primary immunogenicity endpoints of the study will also be assessed by the vaccine 
seroresponse (definition to be provided in the statistical analysis plan [SAP]) against the 
SARS-CoV-2 prototype virus strain and against variant strains including B.1.351. The SRR 
with 95% CI at Day 29 will be summarized for each treatment group. The difference of SRRs 
and 95% CI at Day 29 will be calculated for mRNA-1283 at each dose level and 
mRNA-1283.211 at each dose level compared with mRNA-1273. 
Part B: 
The same analysis methods will be used to analyzed immunogenicity data for Part B, 
ANCOVA model will be used to compare immune response between treatment group 
 
 mRNA-1283.529) in Part B. Day 29 antibody titers (against variant strain B.1.1.529) 
will be included in the model as a dependent variable and treatment group variable 
(mRNA-1283.529  at each dose level) will be included as fixed effect. The model will also 
adjust for age group (< 56, ≥ 56). The GMT will be estimated by the GLSM from the model 
for each group and corresponding 95% CI will be provided. The ratio of GMTs for 
 
mRNA-1283.529 with respect to 
 mRNA-1283.529 will be estimated by the ratio of 
GLSM from the model. The 95% CI for the ratio of GLSM will be provided to assess the 
between-groups difference in immune response against B.1.1.529. 
SRR against B.1.1.529 with 95% CI at Day 29 will be summarized for each mRNA-1283.529 
dose level . The difference of SRRs and 95% CI at Day 29 between two dose levels will also 
be calculated. 
CCI
CCI
CCI
CCI
CCI
CCI
CCI

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Analysis for the Secondary and Exploratory Immunogenicity Objectives: 
Part A and B: 
Immunogenicity, SARS-CoV-2–specific bAb and nAb, will be assessed at multiple time 
points in this study; however, Day 29, 28 days after booster dose, is the time point of primary 
interest. 
For each of the antibodies of interest, eg, levels of SARS-CoV-2–specific bAb and 
SARS-CoV-2–specific nAb, the GMT or level with corresponding 95% CI at each time point 
and geometric mean folder rise of post-baseline/baseline titers or levels with corresponding 
95% CI at each post-baseline time point will be provided by treatment group. The 95% CIs 
will be calculated based on the t-distribution of the log-transformed values, then 
back-transformed to the original scale for presentation. The following descriptive statistics 
will also be provided at each time point: number of participants (n), median, minimum, and 
maximum. 
The SRR of each treatment group against the prototype strain and variant strain, defined as the 
percentage of participants achieving seroresponse against the prototype strain and variant 
strain, respectively, will be provided for each treatment group with the 95% CI calculated 
using the Clopper-Pearson method at each post-baseline time point. 
Subgroup Analyses: 
Part A and B: 
Subgroup analyses may include age and SARS-CoV-2 infection status at baseline depending 
on the sample size in a subgroup. Details will be provided in the SAP. 
Efficacy Analysis: 
Part A and B: 
No pre-specified efficacy analysis will be performed. Exploratory analyses of symptomatic 
and asymptomatic SARS-CoV-2 infection by treatment group may be performed. 
Planned Analyses: 
Primary Analysis 
The primary analysis of safety and immunogenicity will be conducted after Part A participants 
have completed their Day 29 visit assessments. The primary analysis will be performed by a 
separate team of unblinded programmers and statisticians. The analysis, including any cases of 
COVID-19, will be presented by treatment group. With the exception of appropriately 
delegated unblinded study staff, vaccine administrators, and monitors, all personnel involved 
in the conduct of the trial will remain blinded to individual treatment assignment until 

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unblinding. Investigators will be blinded until after the final database lock for final analysis. 
The protocol may be amended to further assess or confirm dose selection based on results of 
this analysis. 
Interim Analysis 
The interim analysis of safety and immunogenicity will be conducted after Part B participants 
have completed their Day 29 visit assessments. The interim analysis will be performed by 
study team programmers and statisticians.  
Final Analysis 
The final analysis of all endpoints will be performed after all participants (Part A and Part B) 
have completed all planned study procedures. Results of this analysis will be presented in a 
final clinical study report (CSR), including individual listings. The final CSR will include full 
analyses of all safety and immunogenicity data through Day 366 (Month 12). 
 
 
 

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TABLE OF CONTENTS 
 
CLINICAL STUDY PROTOCOL .................................................................................. 1 
PROTOCOL APPROVAL – SPONSOR SIGNATORY .................................................. 2 
DECLARATION OF INVESTIGATOR ......................................................................... 3 
PROTOCOL SYNOPSIS................................................................................................ 6 
TABLE OF CONTENTS.............................................................................................. 23 
LIST OF TABLES ....................................................................................................... 28 
LIST OF ABBREVIATIONS ....................................................................................... 29 
GLOSSARY OF TERMS.............................................................................................. 32 
1. 
INTRODUCTION ..................................................................................... 35 
1.1. 
Study Rationale ......................................................................................... 35 
1.2. 
Background and Overview ........................................................................ 37 
1.2.1. 
mRNA-1283 ............................................................................................... 37 
1.2.2. 
mRNA-1283.211 ........................................................................................ 37 
1.2.3. 
mRNA-1283.529 ........................................................................................ 37 
1.2.4. 
Nonclinical Studies ................................................................................... 37 
1.2.5. 
Clinical Studies ......................................................................................... 38 
1.3. 
Benefit/Risk Assessment .......................................................................... 38 
1.3.1. 
Known Potential Benefits ......................................................................... 38 
1.3.2. 
Risks from Study Participation and Their Mitigation ............................. 38 
1.3.3. 
Overall Benefit/Risk Conclusion ............................................................... 40 
2. 
OBJECTIVES AND ENDPOINTS ........................................................... 41 
3. 
STUDY DESIGN ....................................................................................... 44 

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3.1. 
General Design .......................................................................................... 44 
3.2. 
Scientific Rationale for Study Design ....................................................... 46 
3.3. 
Justification for Dose, Control Product, and Choice of Study Population46 
3.4. 
End of Study Definition ............................................................................ 47 
4. 
STUDY POPULATION ............................................................................. 48 
4.1. 
Inclusion Criteria (Part A and Part B) ..................................................... 48 
4.2. 
Exclusion Criteria (Part A and Part B) .................................................... 49 
4.3. 
Lifestyle Restrictions ................................................................................ 50 
4.4. 
Screen Failures ......................................................................................... 50 
5. 
STUDY TREATMENT .............................................................................. 51 
5.1. 
Investigational Products Administered .................................................... 51 
5.2. 
Randomization and Blinding .................................................................... 51 
5.3. 
Preparation/Handling/Storage/Accountability ......................................... 52 
5.3.1. 
Study Vaccine Preparation ....................................................................... 52 
5.3.2. 
Study Vaccine Administration (Part A and Part B) ................................. 52 
5.3.3. 
Study Vaccine Delivery and Receipt ......................................................... 52 
5.3.4. 
Study Vaccine Packaging and Labeling ................................................... 53 
5.3.5. 
Study Vaccine Storage .............................................................................. 53 
5.3.6. 
Study Vaccine Accountability ................................................................... 54 
5.3.7. 
Study Vaccine Handling and Disposal ..................................................... 54 
5.3.8. 
Unblinding (Part A) .................................................................................. 54 
5.4. 
Study Intervention Compliance ................................................................ 55 
5.5. 
Prior and Concomitant Medications (Part A and Part B) ........................ 55 

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5.5.1. 
Prior Medications and Therapies ............................................................. 55 
5.5.2. 
Concomitant Medications and Therapies ................................................. 55 
5.5.3. 
Concomitant Medications and Vaccines that May Lead to the 
Elimination of a Participant from Per-Protocol Analyses ......................... 56 
5.6. 
Intervention After the End of the Study .................................................. 57 
6. 
DELAY OR DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL ......................... 58 
6.1. 
Criteria for Delay of Vaccine Administration .......................................... 58 
6.2. 
Participant Discontinuation/Withdrawal from the Study ....................... 58 
6.3. 
Lost to Follow-up ....................................................................................... 59 
7. 
STUDY ASSESSMENTS AND PROCEDURES (PART A AND PART B)61 
7.1. 
Immunogenicity Assessments .................................................................. 62 
7.2. 
Efficacy Assessments ................................................................................ 63 
7.3. 
Safety Assessments and Procedures ........................................................ 63 
7.3.1. 
Use of Electronic Diaries .......................................................................... 63 
7.3.2. 
Safety Telephone Call ............................................................................... 65 
7.3.3. 
Laboratory Assessments ........................................................................... 66 
7.3.4. 
Vital Sign Measurements ......................................................................... 66 
7.3.5. 
Physical Examinations ............................................................................. 66 
7.3.6. 
Assessment for SARS-CoV-2 Infection ..................................................... 67 
7.4. 
Safety Definitions and Related Procedures .............................................. 69 
7.4.1. 
Adverse Event ........................................................................................... 69 
7.4.2. 
Serious Adverse Events ............................................................................ 69 
7.4.3. 
Solicited Adverse Reactions ...................................................................... 70 

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7.4.4. 
Medically Attended Adverse Events ......................................................... 73 
7.4.5. 
Adverse Event of Special Interest ............................................................ 74 
7.4.6. 
Recording and Follow-up of Pregnancy .................................................... 76 
7.4.7. 
Eliciting and Documenting Adverse Events ............................................. 77 
7.4.8. 
Assessment of Intensity ............................................................................ 77 
7.4.9. 
Assessment of Causality ........................................................................... 78 
7.4.10. 
Reporting Adverse Events ........................................................................ 78 
7.4.11. 
Reporting SAEs ......................................................................................... 79 
7.4.12. 
Time Period and Frequency for Collecting AE, AESI, and SAE 
Information ............................................................................................... 80 
7.4.13. 
Method of Detecting AEs and SAEs ......................................................... 80 
7.4.14. 
Follow-up of AEs and SAEs ...................................................................... 81 
7.4.15. 
Regulatory Reporting Requirements for SAEs ........................................ 81 
7.5. 
Safety Monitoring ..................................................................................... 82 
7.6. 
Treatment of Overdose.............................................................................. 82 
7.7. 
Pharmacokinetics ...................................................................................... 82 
7.8. 
Pharmacodynamics ................................................................................... 82 
7.9. 
Biomarkers ................................................................................................ 82 
7.10. 
Health Economics ..................................................................................... 82 
8. 
STATISTICAL ANALYSIS PLAN ............................................................ 83 
8.1. 
Blinding and Responsibility for Analyses ................................................ 83 
8.2. 
Statistical Hypotheses .............................................................................. 83 
8.3. 
Sample Size Determination ...................................................................... 83 
8.4. 
Analysis Sets ............................................................................................. 83 

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8.5. 
Statistical Methods ................................................................................... 84 
8.5.1. 
Baseline Characteristics and Demographics ............................................ 84 
8.5.2. 
Efficacy Analysis ....................................................................................... 84 
8.5.3. 
Safety Analyses ......................................................................................... 84 
8.5.4. 
Immunogenicity Analyses ......................................................................... 86 
8.5.5. 
Subgroup Analyses .................................................................................... 88 
8.6. 
Planned Analyses ...................................................................................... 88 
8.6.1. 
Primary Analysis ...................................................................................... 88 
8.6.2. 
Interim Analysis ....................................................................................... 88 
8.6.3. 
Final Analysis ........................................................................................... 88 
9. 
REFERENCES .......................................................................................... 89 
10. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS ................................................................................. 92 
10.1. 
APPENDIX 1: Schedule of Events ............................................................ 93 
10.2. 
APPENDIX 2: Study Governance Considerations ................................... 97 
10.2.1. 
Regulatory and Ethical Considerations.................................................... 97 
10.2.2. 
Study Monitoring ...................................................................................... 97 
10.2.3. 
Audits and Inspections ............................................................................. 98 
10.2.4. 
Financial Disclosure ................................................................................. 99 
10.2.5. 
Recruitment Procedures ........................................................................... 99 
10.2.6. 
Informed Consent/Assent Process ............................................................ 99 
10.2.7. 
Protocol Amendments ............................................................................. 100 
10.2.8. 
Protocol Deviations ................................................................................. 101 
10.2.9. 
Data Protection ....................................................................................... 101 

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10.2.10. 
Sample Retention and Future Biomedical Research ............................. 102 
10.2.11. 
Safety Oversight ..................................................................................... 102 
10.2.12. 
Dissemination of Clinical Study Data .................................................... 103 
10.2.13. 
Data Quality Assurance and Quality Control ........................................ 103 
10.2.14. 
Data Collection and Management .......................................................... 104 
10.2.15. 
Source Documents ................................................................................... 105 
10.2.16. 
Retention of Records ............................................................................... 105 
10.2.17. 
Study and Site Closure ........................................................................... 105 
10.2.18. 
Publication Policy .................................................................................... 106 
10.3. 
APPENDIX 3: Contraceptive Guidance ................................................. 107 
10.4. 
APPENDIX 4: Adverse Events of Special Interest Terms for mRNA-
1273 ......................................................................................................... 109 
10.5. 
APPENDIX 5: Protocol Amendment History ......................................... 112 
 
 
LIST OF TABLES 
Table 1: 
Part A Objectives and Endpoints ................................................................................41 
Table 2: 
Part B Objectives and Endpoints ................................................................................42 
Table 3: 
Part A Treatment Groups ............................................................................................44 
Table 4: 
Part B Treatment Groups ............................................................................................45 
Table 5: 
Solicited Adverse Reactions and Grades ....................................................................71 
Table 6: 
Analysis Sets (same definition across part A and B if applicable) .............................84 
Table 7: 
Analysis Strategy for Safety Parameters ....................................................................86 
Table 8: 
Schedule of Events for Part A and Part B ...................................................................93 
 

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LIST OF ABBREVIATIONS 
The following abbreviations and terms are used in this study protocol. 
Abbreviation or Specialist Term 
Definition 
AE 
adverse event 
AESI 
adverse event of special interest 
ANCOVA 
analysis of covariance 
AR 
adverse reaction 
bAb 
binding antibody 
CDC 
US Centers for Disease Control and Prevention 
CEAC 
cardiac event adjudication committee 
CFR 
Code of Federal Regulations 
cMRI 
cardiac magnetic resonance imaging 
CoV 
coronavirus 
COVID-19 
coronavirus disease 2019 
CRO 
contract research organization 
CSR 
clinical study report 
DSMB 
Data Safety Monitoring Board 
DSPC 
1,2-distearoyl-sn-glycero-3-phosphocholine 
ECG/EKG 
electrocardiogram 
eCRF 
electronic case report form 
EDC 
electronic data capture 
eDiary 
electronic diary 
EoS 
end of study 
EUA 
Emergency Use Authorization 
FAS 
Full Analysis Set 
FDA 
US Food and Drug Administration 
FSH 
follicle-stimulating hormone 
GCP 
Good Clinical Practice 
GLSM 
geometric least square mean 
GMFR 
geometric mean fold rise 
GMT 
geometric mean titer 

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Abbreviation or Specialist Term 
Definition 
HATM 
hemagglutinin 
HCP 
healthcare practitioner 
HIPAA 
Health Insurance Portability and Accountability Act 
HRT 
hormone replacement therapy 
IB 
Investigator’s Brochure 
ICF 
informed consent form 
ICH 
International Council for Harmonisation 
IM 
intramuscular 
IP 
investigational product 
IRB 
institutional review board 
LNP 
lipid nanoparticle 
LTFU 
lost to follow-up 
MAAE 
medically attended adverse event 
MedDRA 
Medical Dictionary for Regulatory Activities 
mRNA 
messenger ribonucleic acid 
nAb 
neutralizing antibody 
NP 
nasopharyngeal 
NTD 
N-terminal domain 
PEG-2000-DMG 
1 monomethoxypolyethyleneglycol-2,3-dimyristylglycerol 
with polyethylene glycol of average molecular weight 2000 
PP 
Per-Protocol 
RBD 
receptor-binding domain 
RT-PCR 
reverse transcriptase polymerase chain reaction 
S 
spike 
SAE 
serious adverse event 
SAP 
statistical analysis plan 
SARS 
severe acute respiratory syndrome 
SARS-CoV-2 
severe acute respiratory syndrome coronavirus 2 
SoE 
schedule of events 
SRR 
seroresponse rate 

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Abbreviation or Specialist Term 
Definition 
USP 
US Pharmacopeia 
VOC 
variant of concern 
WHO 
World Health Organization 
 
 
 

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GLOSSARY OF TERMS 
Term/Concept 
Definition 
Adequate female 
contraception 
Consistent and correct use of a Food and Drug Administration–
approved contraceptive method in accordance with the product label. 
AE 
Any untoward medical occurrence associated with the use of a drug in 
humans, whether or not considered drug related. 
AESI 
An AE (serious or nonserious) 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. 
A list of the AESIs pertinent to this study is provided in Section 10.4 
(Appendix 4). 
AR 
Any AE for which there is a reasonable possibility that the vaccine 
caused the AE. For the purposes of investigational new drug safety 
reporting, “reasonable possibility” means that there is evidence to 
suggest a causal relationship between the vaccine and the AE. 
Solicited ARs are defined in Section 7.4.3. 
Anaphylaxis 
An acute hypersensitivity reaction with multiorgan 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. 
Characteristics of anaphylaxis are provided in Section 7.4.4. 
Asymptomatic 
SARS-CoV-2 
infection 
Asymptomatic SARS-CoV-2 infection is defined as a positive 
RT-PCR test on a respiratory sample in the absence of COVID-19 
symptoms or a positive serologic test for anti-nucleocapsid antibody 
after a negative test at time of enrollment.  
COVID-19 
symptoms 
• Fever (temperature ≥ 38.0°C [100.4°F]) or chills 
• Cough 
• Shortness of breath and/or difficulty breathing 
• Fatigue 
• Muscle or body aches 
• Headache 
• New loss of taste and/or smell 
• Sore throat, congestion, or runny nose 
• Nausea or vomiting 

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Term/Concept 
Definition 
• Diarrhea 
Phase 3 study 
(mRNA-1273-P301) 
definition of 
COVID-19 
The participant must have experienced at least TWO of the following 
systemic symptoms: Fever (≥ 38°C), 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 one NP swab, nasal swab, or saliva 
sample (or respiratory sample, if hospitalized) positive for 
SARS-CoV-2 by RT-PCR. 
End of Study (EoS) 
Completion of the last visit of the last participant in the study or last 
scheduled procedure, as shown in the schedule of events (Table 8) for 
the last participant in the study. 
Lost to follow-up 
(LTFU) 
A participant who repeatedly fails to return for scheduled visits 
without stating an intention to withdraw consent and is unable to be 
contacted by the study site.  
MAAE 
An AE that leads to an unscheduled visit to a healthcare provider. 
Nonchildbearing 
potential 
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). 
Screen failures 
Participants who consent to participate in the clinical study but are not 
subsequently assigned to treatment. 
SAE 
An AE is considered an SAE if, in the view of either the investigator 
or Sponsor, it results in any of the following outcomes (see 
Section 7.4.2 for further details of each criterion): 
• Death 
• Is life-threatening 
• Inpatient hospitalization or prolongation of existing 
hospitalization 
• Persistent or significant incapacity or substantial disruption of 
the ability to conduct normal life functions 
• Congenital anomaly or birth defect 
• Medically important event. 

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Term/Concept 
Definition 
Symptomatic 
COVID-19 
The presence of one of the CDC-listed symptoms 
(https://www.cdc.gov/coronavirus/2019-ncov/symptoms-testing/symp
toms.html) and a positive RT-PCR test on a respiratory sample. 
Unsolicited AE 
Any AE reported by the participant that is not specified as a solicited 
AR in the protocol or is specified as a solicited AR but starts outside 
the protocol-defined period for reporting solicited ARs (ie, 7 days 
after vaccination). 
Women of 
childbearing potential 
Women of childbearing potential are those who are considered fertile 
following menarche and until becoming postmenopausal unless 
permanently sterile (see Section 10.3, Appendix 3). 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; 
CDC = US Centers for Disease Control and Prevention; COVID-19 = coronavirus disease 2019; 
MAAE = medically attended adverse event; NP = nasopharyngeal; RT-PCR = reverse transcriptase 
polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory 
syndrome coronavirus 2. 

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1. 
INTRODUCTION 
1.1. 
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 and severe acute 
respiratory syndrome (SARS). An outbreak of a novel coronavirus (coronavirus disease 2019 
[COVID-19], later designated severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2]) 
initially emerged in Wuhan, Hubei Province, China in December 2019. The World Health 
Organization (WHO) declared COVID-19 a pandemic on 11 Mar 2020, which continues to have 
major global public health impact with more than 200 million cases and 4.2 million deaths as of 
10 Aug 2021 (WHO 2021). 
ModernaTX, Inc. (the Sponsor)’s scalable messenger ribonucleic acid (mRNA)/lipid 
nanoparticle (LNP) technology platform allowed for a rapid response to the pandemic and was 
used to develop mRNA-1273, a novel LNP-encapsulated mRNA-based vaccine against 
SARS-CoV-2. mRNA-1273 contains a single mRNA that encodes for the full-length 
SARS-CoV-2 spike (S) protein of the Wuhan-Hu-1 SARS-CoV-2 virus, modified with 2 proline 
substitutions within the heptad repeat 1 domain (S-2P) to stabilize the S protein into a prefusion 
conformation. Having achieved the primary endpoint in a pivotal Phase 3 study conducted in 
persons at high risk for SARS-CoV-2 infection, in December 2020, mRNA-1273 was granted 
Emergency Use Authorization (EUA) for the prevention of COVID-19 for individuals 18 years 
of age and older based on the demonstration of efficacy and safety in a pivotal Phase 3 trial 
(Baden et al 2021). 
In addition to mRNA-1273, the Sponsor is using its mRNA-based platform to develop additional 
SARS-CoV-2 mRNA vaccine candidates that may have improved stability and/or may be as 
immunogenic as mRNA-1273 at a lower dose level. mRNA-1283 encodes for a protein made up 
of 2 segments, the SARS-CoV-2 N-terminal domain (NTD) and receptor-binding domain 
(RBD), which are linked together with a 7-amino-acid flexible linker. These three proteins 
(NTD, RBD, and linker) are attached to a 23-amino-acid transmembrane domain from influenza 
hemagglutinin (HATM) via a 5-amino-acid flexible linker. This entire protein makes up the 
NTD-RBD-HATM antigen and is encoded by mRNA-1283. The mRNA-1283-P101 Phase 1 
study is ongoing (NCT04813796). 
Over the course of the pandemic, SARS-CoV-2 variants have emerged and are likely to continue 
to emerge, some of which may prove to have some level of escape from immunity associated 
with previous infection or vaccination. The emergence of variants of concern (VOCs) or interest, 
as defined by the WHO (WHO 2021), are associated with increased infectivity and a reduction in 
the ability of convalescent sera or sera from vaccinated subjects to neutralize these emergent 
strain variants. Mutations occurring in the RBD are of particular concern, as this site includes the 

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dominant neutralization epitopes on the S protein, and these mutations could impact the 
effectiveness of antibodies elicited by infection or vaccination in neutralizing the virus 
(Greaney et al 2021). 
These recent evolutionary events indicate that SARS-CoV-2 has the capacity to develop more 
efficient transmission between human hosts (Martin et al 2021) and vaccination strategies to 
control the virus need to be responsive to this evolution. A SARS-CoV-2 variant, B.1.1.7, rapidly 
spread from southeast England around the globe. Relative to the Wuhan viral isolate, B.1.1.7 
includes 8 mutations located in the S protein, including the N501Y mutation occurring in the 
RBD. Early analyses indicate that B.1.1.7 has a substantial fitness advantage over other currently 
circulating lineages. The B.1.351 variant emerged in South Africa, and the P.1 lineage has 
recently been reported in Brazil. For the P.1 lineage, there are at least 11 mutations located in the 
S protein, 3 of which (K417N, E484K, and N501Y) are found in the RBD. More recently, 
SARS-CoV-2 variants emerged in India, and the B.1.617.2 variant (Delta variant) containing 2 
mutations in the RBD (L452R and T478K) is now circulating globally. In vitro characterization 
of sera from individuals recently vaccinated with the 2-dose regimen of the Moderna COVID-19 
vaccine at the 100 µg dose showed that the Moderna COVID-19 vaccine (mRNA-1273) 
produced neutralizing titers against key emerging variants tested, including B.1.1.7, B.1.351, and 
B.1.617.2 (Wang et al 2021, Wu et al 2021, Choi et al 2021). The studies showed no significant 
reduction in neutralizing titers against the B.1.1.7 relative to the prototype Wuhan-Hu-1 strain 
and a 2.1-fold reduction versus B.1.617.2; however, a greater than 6-fold reduction in 
neutralizing titers was observed against the B.1.351 variant relative to the Wuhan-Hu-1. There is 
clinical and epidemiologic evidence that these VOCs have increased virulence, resulting in 
higher rates of hospitalization and death (Abdool Karim et al 2021), and there is evidence of 
reduced vaccine efficacy against the B.1.351 virus from Phase 3 clinical trials with 
non-mRNA-based vaccines that enrolled participants in South Africa (Madhi et al 2021, Shinde 
et al 2021). Evidence of effectiveness for an mRNA-based vaccine was recently published, 
which demonstrated protection against the B.1.351 and B.1.1.7 variants after implementation of 
an mRNA COVID-19 vaccine in Qatar (Abu-Raddad et al 2021). 
Based on the data acquired for mRNA-1273, available under the EUA, and leveraging the 
flexible nature of the mRNA-technology, the Sponsor is evaluating multiple mRNA vaccines to 
address emerging variants. The ongoing pandemic and waning or reduced immunity from 
vaccines or previous infection against VOCs necessitate the development of vaccines and 
vaccination strategies that induce broader protection to decrease morbidity, mortality, and 
transmission. Based on the available data and the potential importance to maintain efficacy 
against the prototype strain or variants more closely related to the B.1.351 strain, the Sponsor has 
developed a multivalent mRNA-1283 vaccine (mRNA-1283.211) composed of equal amounts of 
the mRNA-1283 prototype vaccine and mRNA-1283.351, which encodes for the B.1.351 RBD 

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and NTD of the SARS-CoV-2 S protein, to include in further evaluation of mRNA-1283 in a 
Phase 2a clinical trial. 
Potent neutralizing antibodies (nAbs) to the RBD and NTD of SARS-CoV-2 have been 
described in the literature (Brouwer et al 2020, Liu et al 2020, Lv et al 2020) and support their 
inclusion in candidate vaccines for SARS-CoV-2. Animal challenge and protection studies have 
demonstrated protective responses elicited by RBD-based vaccines (Chen et al 2020, Yang et al 
2020). The NTD and RBD are dominant targets for nAbs to SARS-CoV-2. 
The primary objective of this study is to assess the immunogenicity and safety of mRNA-1283 
and mRNA-1283.211 as a booster dose for those previously vaccinated with mRNA-1273. 
1.2. 
Background and Overview 
The Sponsor has developed a rapid-response, proprietary vaccine platform based on an 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. 
1.2.1. 
mRNA-1283 
In December 2020, mRNA-1273 was granted EUA for the prevention of COVID-19 for 
individuals 18 years of age and older based on the demonstration of efficacy and safety in a 
pivotal Phase 3 trial. The Sponsor is using its mRNA-based platform to develop mRNA-1283, a 
novel LNP-encapsulated, mRNA-based SARS-CoV-2 vaccine candidate that may have improved 
stability and/or may be as immunogenic as mRNA-1273 at a lower dose level. 
1.2.2. 
mRNA-1283.211 
This is a multivalent mRNA-1283 vaccine candidate composed of equal amounts of the 
mRNA-1283 prototype vaccine and mRNA-1283.351. 
1.2.3. 
mRNA-1283.529 
mRNA-1273.529 is a vaccine candidate containing an mRNA encoding for the RBD and NTD of 
the B.1.1.529 variant. 
1.2.4. 
Nonclinical Studies 
Previous nonclinical studies in Balb/c mice have been performed to evaluate dose ranging 
responses to mRNA-1283 (immunogenicity) versus mRNA-1273. These nonclinical studies in 
mice assessed immunogenicity by evaluating binding antibody (bAb) and nAb responses as well 
as Th1-directed CD4+ and CD8+ responses elicited by mRNA-1283. mRNA-1283 was shown to 
be immunogenic in Balb/c mice, demonstrating a bAb response and neutralization activity. 

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mRNA-1283–elicited CD4+ T-cells re-stimulated with S1 or S2 peptide pools exhibited a 
Th1-dominant response (production of interferon-γ, interleukin-2, tumor necrosis factor-α), as 
well as CD8+ T cells, particularly at higher immunogen doses. 
The Sponsor has conducted preclinical evaluation of mRNA-1283 that has been modified to 
encode the SARS-CoV-2 B.1.351 VOC, which indicates reduced neutralization activity to the 
prototype strain. This loss of neutralizing activity is restored by a multivalent mRNA-1283.211 
with mRNAs encoding both the prototype Wuhan-Hu-1 and B.1.351 sequences. Preclinical 
evaluations have also been performed to evaluate mRNA-1283 and mRNA-1283.211 as boosters 
in animals previously vaccinated with a 2-dose primary series of mRNA-1273 or mRNA-1283. 
All boosters significantly increase bAb and nAb titers, with mRNA-1283.211 increasing titers to 
the highest levels against the broadest panel of variants. 
1.2.5. 
Clinical Studies 
The mRNA-1283-P101 Phase 1 study is ongoing (NCT04813796). 
1.3. 
Benefit/Risk Assessment 
1.3.1. 
Known Potential Benefits 
The following benefits may accrue to participants who receive the mRNA-1283 vaccines: 
• The mRNA-1283 vaccines may provide an effective immune response against 
SARS-CoV-2 and VOCs.   
• Participants will have a baseline (Day 1) evaluation for SARS-CoV-2 infection and 
ongoing surveillance for COVID-19 throughout the study. 
• The study will contribute to the development of a vaccine against COVID-19, a 
current pandemic disease. 
1.3.2. 
Risks from Study Participation and Their Mitigation 
Safety will be monitored throughout the study (Section 7.4). 
The safety profile of mRNA-1283 has not been evaluated yet in clinical studies, although a 
Phase 1 study (NCT04813796) is ongoing. 
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 injection. 

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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. 
Intramuscular (IM) injection with other mRNA vaccines manufactured by the Sponsor 
containing the SM-102 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 injection. 
Laboratory abnormalities (including increases in liver function tests and serum lipase levels) 
following injection 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 
available in the mRNA-1283 Investigator’s Brochure (IB). 
mRNA-1273 
The safety profile of mRNA-1273 is largely based on data from the pivotal Phase 3 study. The 
most frequently reported adverse reactions (ARs) after any dose in the vaccine group were pain 
at the injection site, fatigue, headache, myalgia, and chills. The most common solicited local AR 
was pain. The majority of local and systemic ARs had a median duration of 1 to 3 days. Overall, 
there was a higher reported rate of some ARs in younger age groups: the incidence of axillary 
swelling/tenderness, fatigue, headache, myalgia, arthralgia, chills, nausea/vomiting, and fever 
was higher in adults aged 18 to < 65 years than in those aged 65 years and above. 
Several participants reported injection site reactions after Day 7 that were characterized by 
erythema, induration, and often pruritus. These were most likely dermal hypersensitivity and 
were unlikely to represent a long-term safety concern. Hypersensitivity events included injection 
site rash and injection site urticaria, which are likely related to vaccination. There have been no 
cases of severe hypersensitivity or anaphylactic reactions reported immediately after vaccination 
in the trial to date. In the Post-Authorization setting, anaphylaxis has been reported following 
mRNA-1273 administration. 
In addition, there have been very rare reports of myocarditis and pericarditis occurring after 
vaccination with the Moderna COVID-19 vaccine. 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. Healthcare 
professionals should be alert to the signs and symptoms of myocarditis and pericarditis. Detailed 

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information about the known and expected benefits and risks of mRNA-1273 is provided in the 
IB. 
1.3.3. 
Overall Benefit/Risk Conclusion 
The evolving antigenic variation of SARS-CoV-2 underscores the urgent need for vaccination 
strategies that induce broader protection, specifically against VOCs with attendant risk of viral 
escape. The Sponsor is developing additional SARS-CoV-2 mRNA vaccine candidates that may 
have improved stability and/or may be as immunogenic as mRNA-1273 at a lower dose level. 
The present study will evaluate the safety and immunogenicity of these additional vaccine 
candidates.   

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2. 
OBJECTIVES AND ENDPOINTS 
The objectives that will be evaluated in this study and the endpoints and time points associated 
with each objective are provided in Table 1. 
Table 1: Part A Objectives and Endpoints 
Objectives 
Endpoints 
Primary 
 
• 
To assess the safety and reactogenicity of 
the study vaccine candidates 
• 
Frequency and grade of each solicited local 
and systemic reactogenicity AR during a 
7-day follow-up period after vaccination 
• 
Frequency and severity of any unsolicited 
adverse events (AEs) during the 28-day 
follow-up period after vaccination 
• 
Frequency of any serious AEs (SAEs), 
medically attended AEs (MAAEs), AEs 
leading to withdrawal from study 
participation, and AEs of special interest 
(AESIs) from Day 1 to end of study (EoS) 
• 
To assess the immunogenicity of the 
study vaccine candidates 
• 
Immune response of the study vaccine 
candidates against the ancestral severe acute 
respiratory syndrome coronavirus 2 
(SARS-CoV-2) and against SARS-CoV-2 
variants, including B.1.351, at Day 29 by 
geometric mean titer (GMT), geometric 
mean fold rise (GMFR), and seroresponse 
rate (SRR) 
• 
To compare the immune response elicited by 
the mRNA-1283 study vaccine candidates 
with the immune response elicited by the 
mRNA-1273 vaccine when administered as a 
booster at Day 29 by GMT, GMFR, and SRR 
Secondary 
 
• 
To evaluate the immunogenicity at all 
immunogenicity time points 
• 
Immune response of the study 
vaccinecandidates against ancestral 
SARS-CoV-2 and against SARS-CoV-2 
variants at all immunogenicity time points by 
GMT, GMFR, and SRR 

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Objectives 
Endpoints 
Exploratory 
 
• 
To characterize cellular immunogenicity 
• 
Frequency, magnitude, and phenotype of 
antigen-specific B- and T-cells, to include 
B-cell and T-cell receptor repertoires 
• 
To conduct active detection of 
symptomatic and asymptomatic 
SARS-CoV-2 infection 
• 
Laboratory-confirmed asymptomatic or 
symptomatic SARS-CoV-2 infection will be 
defined in participants: 
− 
Negative SARS-CoV-2 
anti-nucleocapsid antibody blood test at 
Day 1 that becomes positive at Day 29 or 
later, OR 
− 
Positive SARS-CoV-2 reverse 
transcriptase polymerase chain reaction 
(RT-PCR) from nasopharyngeal swab 
• 
To assess the genetic and/or phenotypic 
relationships of isolated SARS-CoV-2 
strains to the vaccine sequence 
• 
Comparison of the SARS-CoV-2 genetic 
sequence of viral isolates with the vaccine 
sequence and characterization of immune 
responses to vaccine breakthrough isolates 
Table 2: Part B Objectives and Endpoints 
Objectives 
Endpoints 
Primary 
• 
To assess the safety and reactogenicity of 
the mRNA-1283.529 booster vaccine 
candidate 
• 
Frequency and grade of each solicited local 
and systemic reactogenicity AR during a 
7-day follow-up period after vaccination 
• 
Frequency and severity of any unsolicited 
AEs during the 28-day follow-up period 
after vaccination 
• 
Frequency of any SAEs, MAAEs,  AEs 
leading to withdrawal from study 
participation, and AESIs from Day 1 to 
EoS 
• 
To assess the immunogenicity of the 
mRNA-1283.529 booster vaccine 
candidate as the second booster dose 
• 
Immune response of the mRNA-1283.529 
booster vaccine candidate against 
SARS-CoV-2 Omicron variant (B.1.1.529) 
at Day 29 by GMT, GMFR, and SRR 
Secondary 

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Objectives 
Endpoints 
• 
To assess the immunogenicity at all 
immunogenicity time points 
• 
Immune response of the mRNA-
1283.529 vaccine candidate against the 
ancestral SARS-CoV-2 and against 
SARS-CoV-2 variants at all 
immunogenicity time points by GMT, 
GMFR, and SRR 
• 
 
Exploratory 
• 
To 
characterize 
cellular 
immunogenicity 
• 
Frequency, magnitude, and phenotype 
of antigen-specific B- and T-cells, to 
include B-cell and T-cell receptor 
repertoires 
To conduct active detection of symptomatic 
and asymptomatic SARS-CoV-2 infection 
• 
Laboratory-confirmed asymptomatic or 
symptomatic SARS-CoV-2 infection will be 
defined in participants: 
− 
Negative SARS-CoV-2 
anti-nucleocapsid antibody blood test at 
Day 1 that becomes positive at Day 29 
or later, OR 
− 
Positive SARS-CoV-2 RT-PCR from 
nasopharyngeal swab 
• 
To evaluate the genetic and/or phenotypic 
relationships of isolated SARS-CoV-2 
strains to the vaccine sequence 
• 
Comparison of the SARS-CoV-2 genetic 
sequence of viral isolates with the vaccine 
sequence and characterization of immune 
responses to vaccine breakthrough isolates 
 

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3. 
STUDY DESIGN 
3.1. 
General Design 
This is a Phase 2a study that consists two parts: Part A is an observer-blind, stratified, 
randomized design to evaluate the immunogenicity, safety, and reactogenicity of mRNA-1283, 
mRNA-1283.211, mRNA-1273, and potentially of other study vaccine candidates administered 
as a single booster dose to participants 18 years and older who were previously vaccinated with 
mRNA-1273. Part B is an open-label design to evaluate the immunogenicity, safety, and 
reactogenicity of mRNA-1283.529 administered as a single booster dose to participants 18 years 
and older who were previously vaccinated with mRNA-1273. 
Part A of this study will assess whether a single dose of mRNA-1283 at three different doses 
 or mRNA-1283.211 at two different dose levels 
 will boost 
antibody responses to the Wuhan-Hu-1 (ancestral strain of SARS-CoV-2) virus, and to the 
B.1.351 variant, and potentially other SARS-CoV-2 variants, and it will also be used to select a 
dose for subsequent clinical evaluation. The study will include an active comparator group of 
participants who will receive mRNA-1273 
. 
Participants in Part A who received the primary series of mRNA-1273 
 with appropriate 
documentation at least 6 months prior will be randomized 1:1:1:1:1:1 to receive a single boost of 
mRNA-1283 at one of three dose levels, a single boost of mRNA-1283.211 at one of two dose 
levels, or a single dose of the active comparator, mRNA-1273 (Error! Reference source not 
found.). 
Table 3: Part A Treatment Groups 
Treatment Group 
Vaccine 
Dose Level1 
N 
1 
mRNA-1283 
70 
2 
70 
3 
70 
4 
mRNA-1283.211 
70 
5 
70 
6 
mRNA-1273 
70 
1 Dose levels for mRNA-1283.211 and mRNA-1273 are total mRNA in 1:1 ratio of mRNA-1283 and mRNA-1283.351 or 
mRNA-1273 and mRNA-1283.351, respectively. 
Part B of this study will assess whether a single dose of mRNA-1283.529 as the second booster 
at two different dose levels 
 as the second booster after a first booster of mRNA-
1273 
, at least 3 months prior, will boost antibody response to the ancestral strain of the 
SARS-CoV-2 virus, the B.1.1.529 variant, and potentially other SARS-CoV-2 variants, and 
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inform dose selection for mRNA-1283.529 booster vaccine candidate for subsequent clinical 
evaluation. 
Participants in Part B who received the primary series of mRNA 1273 and who received a first 
booster dose of mRNA-1273 
 at least 3 months prior will be enrolled in a 1:1 ratio to 
receive a single boost of mRNA 1283.529 at one of two dose levels (Table 4). 
Table 4: Part B Treatment Groups 
Treatment Group 
Vaccine 
Dose Level1 
N 
1 
mRNA-1283.529 
 
70 
2 
 
70 
Enrollment in both parts of this study will be stratified by age with two age strata: 18-55 years of 
age and ≥ 56 years of age, with at least 20% but not more than 50% of participants 56 years of 
age or older. Those with documented prior SARS-CoV-2 infection are eligible to participate if 
also previously vaccinated with mRNA-1273. Prior infection status will be confirmed by 
anti-nucleocapsid antibody testing of all participants. 
The schedule of events (SoE) table is provided in Table 8. The SoE will be used for participants 
in both parts of the study. Participants will have up to 6 study visits; 5 visits if screening and 
randomization are performed on the same day. Study vaccine will be administered as a single 
dose on Day 1. Additional safety and immunogenicity study visits will occur on Days 8 (safety 
call only), 15, 29, 181, and 366 (EoS). Study visits will include scheduled safety phone calls 
every 2 weeks to collect MAAEs, AESIs, AEs leading to withdrawal, SAEs, and information 
about concomitant medications associated with these events, as well as to collect information 
about receipt of nonstudy vaccinations temporally associated with these events. 
At the vaccination visit (Day 1), participants will be instructed how to document and report 
solicited ARs in a provided electronic diary (eDiary). Solicited ARs will be assessed for 7 days 
after the injection (the day of injection and the following 6 days), and unsolicited AEs will be 
assessed for 28 days after each injection. Medically attended AEs, SAEs, AESIs, and AEs 
leading to withdrawal will be assessed throughout the study. All participants will be tested for 
the presence of SARS-CoV-2 anti-nucleocapsid antibodies at Days 1, 29, 181, and 366, as well 
as by nasopharyngeal (NP) swab RT-PCR on Days 1, 29, 181, and 366. Active surveillance for 
intercurrent or breakthrough SARS-CoV-2 infection will occur throughout the study and be 
reported as AEs (confirmed symptomatic infections will be reported as MAAEs if not an SAE). 
Symptomatic infection will be prompted by signs and symptoms meeting the US Centers for 
Disease Control and Prevention (CDCb 2021) case definition for COVID-19 (05 Aug 2020 or 
most recent), as well as the clinical suspicion of the site investigator. Participants will be asked to 
contact the study site to arrange for a prompt, thorough, and careful assessment. Participants will 
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have blood sampled at scheduled study site visits (Days 1, 15, 29, 181, and 366) during the study 
for immunogenicity assessments or other medical concerns according to the investigator’s 
judgment. 
Participants may experience AEs, including symptoms of COVID-19, 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. 
In addition, participants may have blood sampled at unscheduled visits for acute respiratory 
symptoms. 
3.2. 
Scientific Rationale for Study Design 
Part A of this study is designed as an observer-blind study. Part B of the study is designed as an 
open-label study. 
With SARS-CoV-2 expected to be circulating in the general population during the study, all 
participants will provide pre-injection and post-injection blood samples for analysis of antibodies 
to nonvaccine antigens through 12 months after study injection. In addition, participants will 
have NP swab samples collected before vaccination on Day 1 as well as on Day 29, Day 181, 
and Day 366 (EoS). Furthermore, in case of any signs or symptoms or MAAEs suggesting 
SARS-CoV-2 infection in a participant, an additional NP swab sample and blood sample will be 
collected to confirm the diagnosis of SARS-CoV-2 via serology and RT-PCR. Additionally, 
clinical information will be carefully collected to evaluate the severity of the clinical case. 
Since it is possible that participants are naturally exposed to SARS-CoV-2 through community 
exposure, the NP swab samples collected before study injection and the serologic assays 
performed for antibody responses to nonvaccine antigen(s) may help to discriminate between 
natural infection and vaccine-induced antibody responses, should such discrimination be needed. 
3.3. 
Justification for Dose, Control Product, and Choice of Study Population 
The safety and immunogenicity of mRNA-1283 vaccine is being assessed as a primary series 
administered in two doses administered 28 days apart at three different dose levels of 
 
 in the mRNA-1283-P101 study. Data analysis has not been performed in that study. The 
dose levels for mRNA-1283 and mRNA-1283.211 were selected to assess the dose range for a 
booster dose indication based on data from pre-clinical studies of these vaccines and clinical data 
for mRNA-1273 administered as a booster dose. 
This study will screen and enroll healthy adults, 18 years of age and above, who have previously 
been vaccinated with mRNA-1273. 
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3.4. 
End of Study Definition 
A participant is considered to have completed the study if he or she has completed all phases of 
the study including the last scheduled procedure as shown in the SoE (Table 8). 
The EoS is defined as completion of the last visit of the last participant in the study or last 
scheduled procedure, as shown in the SoE (Table 8), for the last participant in the study. 

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4. 
STUDY POPULATION 
In Part A, up to 420 participants previously vaccinated for COVID-19 with mRNA-1273 will 
receive a single boost of mRNA-1283 at one of three dose levels, a single boost of 
mRNA-1283.211 at one of two dose levels, or a single dose of the active comparator, 
mRNA-1273, in a 1:1:1:1:1:1 ratio, ie, up to 70 participants per treatment group. 
In Part B, up to 140 participants will be enrolled in a 1:1 ratio to mRNA-1283.529 at two dose 
levels (ie, up to 70 participants for each treatment group). 
Prospective approval of protocol deviations to recruitment and enrollment criteria, also known as 
protocol waivers or exemptions, is not permitted. 
4.1. 
Inclusion Criteria (Part A and Part B) 
Each participant must meet all of the following criteria to be enrolled in this study: 
1. At least 18 years of age at the time of consent (Screening Visit). 
2. Investigator assessment that participant understands and is willing and physically able to 
comply with protocol-mandated follow-up, including all procedures. 
3. Participant has provided written informed consent for participation in this study, 
including all evaluations and procedures as specified in this protocol. 
4. Female participants of nonchildbearing potential may be enrolled in the study. 
Nonchildbearing potential is defined as bilateral tubal ligation > 1 year prior to screening, 
bilateral oophorectomy, hysterectomy, or menopause. Follicle-stimulating hormone 
(FSH) level may be measured at the discretion of the investigator to confirm 
postmenopausal status. 
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 on the day of vaccination (Day 1). 
• Has practiced adequate contraception or has abstained from all activities that could 
result in pregnancy for at least 28 days prior to Day 1. 
• Has agreed to continue adequate contraception through 3 months following the last 
vaccine administration. 
• Is not currently breastfeeding. 
• Adequate female contraception is defined as consistent and correct use of a US Food 
and Drug Administration (FDA)–approved contraceptive method in accordance with 
the product label. 

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6. Participant must have received their second dose of the mRNA-1273 primary series at 
least 6 months prior to screening and enrollment (Part A) or have received the mRNA-
1273 series and an mRNA-1273 booster dose (50 ug) at least 3 months prior to screening 
and enrollment (Part B). 
4.2. 
Exclusion Criteria (Part A and Part B) 
Participants meeting any of the following criteria will be excluded from the study: 
1. Had significant exposure to someone with SARS-CoV-2 infection or COVID-19 in the 
past 14 days, defined by the CDC (CDCa 2021) as a close contact of someone who has 
COVID-19. 
2. Is acutely ill or febrile (temperature ≥ 38.0°C/100.4°F) less than 72 hours prior to or at 
the Screening Visit or Day 1. Participants meeting this criterion may be rescheduled and 
will retain their initially assigned participant number. 
3. Currently has symptomatic acute or unstable chronic disease requiring medical or 
surgical care, to include significant change in therapy or hospitalization for worsening 
disease, at the discretion of the investigator. 
4. Has a medical, psychiatric, or occupational condition that may pose additional risk as a 
result of participation, or that could interfere with safety assessments or interpretation of 
results according to the investigator’s judgment. 
5. History of myocarditis, pericarditis, or myopericarditis within 2 months prior to 
Screening. Participants who have not returned to baseline after their convalescent period 
will also be excluded.  
6. Has a current or previous diagnosis of immunocompromising condition to include human 
immunodeficiency virus, immune-mediated disease requiring immunosuppressive 
treatment, or other immunosuppressive condition. 
7. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days in 
total within 6 months prior to screening (for corticosteroids ≥ 10 mg/day of prednisone 
equivalent) or is anticipating the need for immunosuppressive treatment at any time 
during participation in the study. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the injection 
(Day 1) or plans to receive a licensed vaccine within 28 days before or after the study 
injection, with the exception of influenza vaccines, which may be given 14 days before or 
after receipt of a study vaccine. 
9. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive these during the study. 

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10. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
11. Plans to participate in an interventional clinical trial of an investigational vaccine or drug 
while participating in this study. 
12. Is an immediate family member or household member of study personnel, study site staff, 
or Sponsor personnel. 
4.3. 
Lifestyle Restrictions 
Participants must not eat or drink anything hot or cold within 10 minutes before oral temperature 
is taken. 
4.4. 
Screen Failures 
Screen failures are defined as participants who consent to participate in the clinical study but are 
not subsequently 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 publishing requirements and to respond to queries from regulatory authorities. 
Minimum information includes date of informed consent, demography, reason(s) for screen 
failure, eligibility criteria, and information on any SAE that may have occurred from the time 
informed consent was obtained to the time of withdrawal. 

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5. 
STUDY TREATMENT 
5.1. 
Investigational Products Administered 
The term “investigational product (IP)” refers to the mRNA-1283, mRNA-1283.211, 
mRNA-1273, and mRNA-1283.529 vaccine candidates and mRNA-1273 vaccine administered 
in this study. 
The mRNA-1283 Drug Product is an LNP dispersion containing a single mRNA sequence that 
encodes a protein made up of 2 segments of the SARS-CoV-2 S protein: the NTD and RBD, 
which are linked together with a 7-amino-acid flexible linker. These three proteins (NTD, RBD, 
and linker) are attached to a 23-amino-acid transmembrane domain from influenza HATM via a 
5-amino-acid flexible linker. This entire protein makes up the NTD-RBD-HATM antigen and is 
encoded by mRNA-1283. The mRNA is combined in a mixture of 4 lipids common to the 
Sponsor’s mRNA vaccine platform: 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 (PEG-2000-DMG). 
mRNA-1283 is provided as a sterile liquid for injection, as a white to off-white dispersion in 
appearance, at a concentration of 0.4 mg/mL in 20 mM Tris buffer containing 87 mg/mL sucrose 
and 10.7 mM sodium acetate, at pH 7.5. mRNA-1283 is packaged in 2R US Pharmacopeia 
(USP) Type I borosilicate glass vials with a PLASCAP® vial seal containing a 13-mm 
FluroTec-coated plug stopper and has a 0.6-mL nominal fill volume. 
mRNA-1273 is an LNP dispersion of an mRNA encoding the full-length prefusion stabilized 
S protein of SARS-CoV-2 formulated in LNPs as described for mRNA-1283. mRNA-1273 
injection is provided as a sterile liquid for injection, 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 4.3 mM 
sodium acetate, at pH 7.5. 
5.2. 
Randomization and Blinding 
Randomization will be performed using an interactive response technology (IRT). Participants in 
Part A will be randomized in parallel according to a 1:1:1:1:1:1 ratio (Arm 1: Arm 2: Arm 3: 
Arm 4: Arm 5: Arm 6). Participants in Part B will be enrolled in the two arms sequentially. 
Enrollment in both parts of this study will be stratified by age with two age strata: 18-55 years of 
age and ≥ 56 years of age, with at least 20% but not more than 50% of participants 56 years of 
age or older. All participants, study staff involved in participant assessment, and Sponsor 
personnel (or its designees) will be blinded to vaccination assignment until the EoS for Part A. 
Preparation of IP for administration will be conducted on site by an unblinded staff member who 
has no role in the observation or assessment of study participants. A limited number of Sponsor 
and/or contract research organization (CRO) personnel will be unblinded to perform Data Safety 

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Monitoring Board (DSMB) safety data reviews. Additional information regarding unblinding is 
provided in Section 5.3.8. Part B of the study is open-label and therefore unblinded.  
5.3. 
Preparation/Handling/Storage/Accountability 
5.3.1. 
Study Vaccine Preparation 
Each dose of IP in Part Awill be prepared for each participant based on the treatment group. 
Each injection will have a volume of 0.25 mL. The vaccines will contain mRNA-1283 at the 
doses of 
, mRNA-1283.211 at the doses of 
 
, and mRNA-1273 at the dose of 
.  
Each dose of IP in Part B will be prepared for each participant based on the treatment group. 
Each injection will have a volume of 0.25 mL. The vaccines will contain mRNA-1283.529 at the 
doses of 
.  
Vaccine preparation instructions are detailed in the mRNA-1283-P201 Pharmacy Manual. 
5.3.2. 
Study Vaccine Administration (Part A and Part B) 
Investigational product will be administered as an IM injection into the deltoid muscle on Day 1. 
Preferably, vaccine should be administered into the nondominant arm. 
On Day 1, participants will be monitored for a minimum of 30 minutes after vaccination. 
Assessments will include vital sign measurements and monitoring for local or systemic ARs as 
shown in the SoE (Table 8). 
The study site will be appropriately staffed with individuals with basic cardiopulmonary 
resuscitation training/certification. Either onsite resuscitation equipment or appropriate protocols 
for the rapid transport of a participant to a resuscitation area or facility are required. 
5.3.3. 
Study Vaccine Delivery and Receipt 
The Sponsor or designee is responsible for the following: 
• Supplying the IP 
• Confirming the appropriate labeling of the IP, so that it complies with the legal 
requirements of the United States 
The investigator is responsible for acknowledging the receipt of the IP by a designated staff 
member at the site, which includes the following: 
• Confirming that the IP was received in good condition 
• Confirming that the temperature during shipment from the Sponsor to the 
investigator’s designated storage location was appropriate 
CCI
CCI
CCI
CCI

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• Confirming that the Sponsor has authorized the IP for use 
• Ensuring the appropriate dose of IP is properly prepared using aseptic technique 
Further description of the IP and instructions for the receipt, storage, preparation, administration, 
accountability, and destruction of IP are described in the mRNA-1283-P201 Pharmacy Manual. 
5.3.4. 
Study Vaccine Packaging and Labeling 
The Sponsor will provide the investigator (via the study site pharmacy) with adequate quantities 
of IP. Sterile mRNA-1283, mRNA-1283.211, and mRNA-1283.529 (0.4 mg/mL) are packaged 
in 2R glass vials with a 0.8-mL fill volume. Sterile mRNA-1273 (0.2 mg/mL) is packaged in 
10R glass vials with a 6.3-mL fill volume. The IP will have all required labeling per regulations 
and will be supplied to the pharmacy in an unblinded manner. 
The Sponsor or Sponsor’s designee will supply the 0.9% sodium chloride injection for use as a 
diluent for the vaccines. The 0.9% sodium chloride bears a commercial label and does not 
contain study-specific identification. 
The IP will be packaged and labeled in accordance with the standard operating procedures of the 
Sponsor or of its designee, Code of Federal Regulations (CFR) Title 21 Good Manufacturing 
Practice guidelines, International Council for Harmonisation (ICH) Good Clinical Practice 
(GCP) Guidance, guidelines for Quality System Regulations, and applicable regulations. 
5.3.5. 
Study Vaccine Storage 
The mRNA-1283, mRNA-1283.211, and mRNA-1283.529 vaccine candidates must be stored 
at -90°C to -60°C (-130°F to -76°F) and the mRNA-1273 vaccines must be stored at -25°C 
to -15°C (-13°F to 5°F) in a secure area with limited access and protected from moisture and 
light until they are prepared for administration (Section 5.3.1). The freezer should have 
automated temperature recording and a 24-hour alert system in place that allows for rapid 
response in case of refrigerator malfunction. There must be an available backup freezer. The 
freezer must be connected to a backup generator. In addition, IP accountability study staff are 
required to keep a temperature log to establish a record of compliance with these storage 
conditions. The site is responsible for reporting any IP that was not temperature-controlled 
during shipment or storage. Such IP will be retained for inspection by the monitor and disposed 
of according to approved methods. 
The 0.9% sodium chloride injection (USP) should be stored at 20°C to 25°C (68°F to 77°F) in a 
restricted access area. 

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5.3.6. 
Study Vaccine Accountability 
It is the investigator’s responsibility that the IP accountability study staff maintain accurate 
records in an IP accountability log of receipt of all IP, site IP inventory, IP dispensing, IP 
injections, and return to the Sponsor or alternative disposition of used and unused IP vials. 
A 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-1283-P201 Pharmacy 
Manual. 
5.3.7. 
Study Vaccine Handling and Disposal 
A site monitor will reconcile the IP inventory during the conduct and at the EoS for compliance. 
Once fully reconciled at the site at the EoS, the IP should be destroyed on site, if site procedures 
allow, or returned to a destruction depot per instruction of the Sponsor. Additional details are 
found in the mRNA-1283-P201 Pharmacy Manual. 
5.3.8. 
Unblinding (Part A) 
Part A of this study is an observer-blind study. The investigator, study staff, study participants, 
site monitors, and Sponsor personnel (or its designees) will be blinded to the IP administered 
until the EoS for Part A, 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. 
• 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. 
• The DSMB will review unblinded statistical outputs for ad hoc safety reviews 
triggered by pause rules, should this occur. See Section 10.2.11 for additional 
information on DSMB and safety review. 
• The pre-identified Sponsor team members will become unblinded to treatment group 
after primary analysis, but not to individual study participant receipt of study vaccine. 

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Except in the case of a medical necessity, a participant’s treatment assignment should not be 
unblinded without the approval of the Sponsor. If a participant becomes seriously ill or pregnant 
during the study, the blind will be broken only if knowledge of the treatment assignment will 
affect that participant’s clinical management. In the event of a medical emergency requiring 
identification of individual treatment assignment, the investigator will make every attempt to 
contact the CRO medical monitor to explain the need for unblinding within 24 hours of opening 
the code. The investigator will be responsible for documenting the time, date, reason for 
unblinding, and the names of the personnel involved. The investigator (or designee) will have 
access to unblind participants within IRT. All unblinding instances will be tracked via an audit 
trail in IRT and documented in the final study report. 
5.4. 
Study Intervention Compliance 
All doses of IP will be administered at the study site under direct observation of medically 
qualified study staff and appropriately recorded (date and time) in the eCRF. Qualified staff will 
confirm that the participant has received the entire dose of IP. If a participant does not receive IP 
or does not receive all of the planned dose, the reason for the missed dose will be recorded. Data 
will be reconciled with site accountability records to assess compliance. 
5.5. 
Prior and Concomitant Medications (Part A and Part B) 
5.5.1. 
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. 
5.5.2. 
Concomitant Medications and Therapies 
At the study site, study staff must question the participant regarding any medications taken and 
nonstudy vaccinations received by the participant and record the following information in the 
eCRF: 
• All nonstudy vaccinations administered within the period starting 28 days before the 
study injection. 
• Seasonal influenza vaccine administered for the current influenza season (typically 
October through April in the Northern Hemisphere). 
• All concomitant medications and nonstudy vaccinations taken through 28 days after 
vaccination. Antipyretics and analgesics taken prophylactically (ie, taken in the 

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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 or its symptoms. 
• Any concomitant medications relevant to or for the treatment of an SAE or an 
MAAE. 
• The 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 vaccination, including 
the day of injection. Reported antipyretic or analgesic medications should be recorded 
in the source document by the study site staff during the post-injection study visits or 
via other participant interactions (eg, telephone calls). 
Concomitant medications (including vaccinations) will be coded using the WHO Drug 
Dictionary. 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 injection of 
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 
interpretation of the data. It is the investigator’s responsibility to ensure that details regarding the 
concomitant medications are adequately recorded in the eCRF. 
5.5.3. 
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 evaluability in the per-protocol 
(PP) analysis (analysis sets are described in Section 8.4): 
• Any investigational or nonregistered product (drug or vaccine) other than the IP used 
during the study period. 
• Immunosuppressants or other immune-modifying drugs administered chronically (ie, 
more than 14 days in total) during the study period. For corticosteroids, this will mean 
that prednisone ≥ 10 mg/day or the equivalent is not permitted. Inhaled, nasal, and 
topical steroids are allowed. 
• Long-acting immune-modifying drugs administered at any time during the study 
period (eg, infliximab). 
• An authorized or licensed vaccine administered during the period from 28 days before 
through 28 days after vaccination, except for any licensed influenza vaccine that was 
administered 14 days before or after vaccination. 

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• Immunoglobulins and/or any blood products administered during the study period. 
5.6. 
Intervention After the End of the Study 
Study intervention will not be available to participants after the EoS. 

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6. 
DELAY OR DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL 
6.1. 
Criteria for Delay of Vaccine Administration 
Body temperature must be measured before vaccination. The following events constitute criteria 
for delay of injection, and if either of these events occur at the time scheduled for vaccination, 
the participant may be injected at a later date within the time window specified in the SoE 
(Table 8), or the participant may be discontinued from vaccination at the discretion of the 
investigator (Section 6.2): 
• Acute moderate or severe infection with or without fever at the time of vaccination 
• Fever, defined as body temperature ≥ 38.0°C (100.4°F) at the time of vaccination 
Afebrile participants with minor illnesses can be vaccinated at the discretion of the investigator. 
Participants with a fever of 38.0°C (100.4°F) or higher will be contacted within the time window 
acceptable for participation and re-evaluated for eligibility. If the investigator determines that the 
participant’s health on the day of vaccination temporarily precludes injection, the visit should be 
rescheduled within the allowed interval for that visit. 
If a participant takes a prohibited drug therapy, an injection could be delayed within the visit 
window based on the joint decision of the investigator and the CRO’s medical monitor 
(Section 5.5.3). 
6.2. 
Participant Discontinuation/Withdrawal from the Study 
Participants who withdraw or are withdrawn from the study will not be replaced. 
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 participant complete all study procedures pending at the time of withdrawal. 
If a participant desires to withdraw from the study because of an AE, the investigator will 
attempt to obtain agreement to follow up with the participant until the event is considered 
resolved or stable and will then complete the EoS 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: 
• AE (specify) 
• AESI (specify) 

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• SAE (specify) 
• Death 
• Lost to follow-up (LTFU) 
• Physician decision (specify) 
• Pregnancy 
• Protocol deviation 
• Study terminated by Sponsor 
• Withdrawal of consent by participant (specify) 
• Other (specify) 
Participants who are withdrawn from the study because of AEs (including SAEs and AESIs) 
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 a result of an 
SAE or AE until resolution of the event. 
A participant withdrawing 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. 
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). 
6.3. 
Lost to Follow-up  
A participant will be considered LTFU if he or she repeatedly fails to return for scheduled visits 
without stating an intention to withdraw consent and is unable to 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 who continues to be unreachable or continues to be noncompliant with 
study visits or procedures will be considered to have withdrawn from the study. 
• A participant should not be considered LTFU until due diligence has been completed. 

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7. 
STUDY ASSESSMENTS AND PROCEDURES (PART A AND PART B) 
Before performing any study procedures, all potential participants will sign an informed consent 
form (ICF) (as detailed in Section 10.2.6). Participants will undergo study procedures at the time 
points specified in the SoE (Table 8). A participant can also 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 telephone calls or send text messages to inform the participant about visits, 
review eDiary requirements, or follow-up on ongoing or outstanding issues. 
The study site staff are responsible for ensuring that participants comply with the allowed study 
visit windows. If a participant misses a visit, every effort should be made to contact the 
participant and complete a visit within the defined visit window specified in the SoE (Table 8). If 
a participant does not complete a visit within the time window, that visit will be classified as a 
missed visit 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. 
In accordance with “FDA Guidance on Conduct of Clinical Trials of Medical Products during 
COVID-19 Public Health Emergency” (DHHS 2020), investigators may convert study site visits 
to home visits or telemedicine visits with the approval of the Sponsor. Such action should be 
taken to protect the safety and well-being of 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 the SoE (Table 8). 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 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 a part of the participant’s routine clinical management and 
obtained before signing of the ICF may be utilized for screening or baseline purposes 
provided that the procedures meet the protocol-specified criteria and are performed 
within the time frame defined in the SoE (Table 8). 

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• The Screening Visit and Day 1 visit may be completed on the same day. 
7.1. 
Immunogenicity Assessments 
Blood samples for immunogenicity assessments will be collected at the time points indicated in 
the SoE (Table 8). The following immunogenicity assessments will be measured: 
• Serum bAb level against SARS-CoV-2, as measured by ligand-binding assay specific 
to the SARS-CoV-2 S protein and the S protein RBD. 
• Serum nAb level against SARS-CoV-2, as measured by pseudovirus neutralization 
assays. 
• The above assays will include SARS-CoV-2 variant antigens, pseudotyped virus 
expressing SARS-CoV-2 S protein, or virus isolates to assess differences in 
immunologic responses to different SARS-CoV-2 variant S proteins. 
• Testing for serologic markers for SARS-CoV-2 infection, as measured by 
anti-nucleocapsid antibodies detected by immunoassay at study enrollment (Day 1) 
and scheduled post-baseline time points. 
Sample aliquots will be designed to ensure that backup samples are available and that vial 
volumes are likely to be adequate for future testing needs. The actual time and date of each 
sample collected will be recorded in the eCRF. Handling and preparation of the samples for 
analysis, as well as shipping and storage requirements, will be provided in a separate study 
manual. 
Measurement of bAb and nAb levels will be performed in a laboratory designated by the 
Sponsor. 
According to the ICF (Section 10.2.6), 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 CoVs. 
The maximum amount of blood collected from each participant over the duration of the study, 
including any extra assessments that may be required, will not exceed blood limits specified by 
local regulations. Repeat or unscheduled samples may be taken for safety reasons or for technical 
issues with the samples. Further details are provided in both the ICF and Laboratory Reference 
Manual. 

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7.2. 
Efficacy Assessments 
Vaccine efficacy will not be formally assessed in this study, but active surveillance for 
COVID-19 and SARS-CoV-2 infection through monthly contact and scheduled blood collection 
(see Table 8) will be performed. 
7.3. 
Safety Assessments and Procedures 
Safety assessments will include monitoring and recording of the following for each participant, 
according to the SoE (Table 8): 
• Solicited local and systemic ARs (Section 7.4.3) that occur during the 7 days 
following vaccination (ie, the day of injection and 6 subsequent days). Solicited ARs 
will be recorded daily using eDiaries (Section 7.3.1). 
• Unsolicited AEs observed or reported during the 28 days following vaccination (ie, 
the day of injection and 27 subsequent days). Unsolicited AEs are defined in 
Section 7.4.1. 
• MAAEs from vaccination on Day 1 through EoS or withdrawal from the study. 
• AESIs from vaccination on Day 1 through EoS or withdrawal from the study. 
• AEs leading to withdrawal from Day 1 through EoS . 
• SAEs from vaccination on Day 1 through EoS or withdrawal from the study. 
• Vital sign measurements before and after vaccine administration 
• Physical examination findings (if performed) 
• Details of all pregnancies in female participants will be collected after the start of 
study treatment and until the end of their participation in the study (Section 7.4.6). 
The incidence and severity of the above events will be monitored by the blinded study team 
members (Section 7.5). 
7.3.1. 
Use of Electronic Diaries 
At the time of consent, the participants must confirm they will be willing to complete an eDiary 
using either an application downloaded to their smartphone or using a device that will be 
provided at the time of enrollment. Before enrollment on Day 1, the participant will be instructed 
to download the eDiary application or will be provided an eDiary device to record solicited ARs 
(Section 7.4.3) on Day 1. 
On Day 1 (vaccination day), participants will be instructed on thermometer usage to measure 
body temperature, ruler usage to measure injection site erythema and swelling/induration 

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(hardness), and self-assessment for localized axillary swelling or tenderness on the same side as 
the injection arm. 
On Day 1 (vaccination day), participants will record data into the eDiary starting approximately 
30 minutes after the injection under supervision of the study site staff to ensure successful entry 
of assessments. The study site staff will perform any retraining as necessary. Participants will 
continue to record data in the eDiary after they leave the study site, preferably in the evening and 
at the same time each day, on the day of injection and for 6 days following injection. 
Participants will record the following data in the eDiary: 
• Solicited local and systemic reactogenicity ARs, as defined in Section 7.4.3, that 
occur on the day of vaccination and during the 7 days after vaccination (ie, the day of 
injection and 6 subsequent days). Any solicited AR that is ongoing beyond Day 7 will 
be reported in the eDiary until it has resolved, and not to exceed 28 days after 
vaccination. Adverse reactions recorded in the eDiary beyond Day 7 should be 
reviewed by the study site staff either during the next scheduled telephone call or at 
the next study site visit. 
• Daily oral body temperature measurement should be performed at approximately the 
same time each day using the thermometer provided by the study site. If body 
temperature is taken more than once in a given day, only the highest temperature 
reading should be recorded. 
• Other measurements, as applicable, for solicited local ARs (injection site erythema 
and swelling/induration) will be performed using the ruler provided by the study site. 
• Any medications taken to treat or prevent pain or fever on Day 1 or for the next 
6 days. 
The eDiary will be the only source document allowed for solicited systemic or local ARs 
(including body temperature measurements). Participants will be instructed to complete eDiary 
entries daily. The participant will have a limited window on the following day to complete 
assessments for the previous day; quantitative temperature recordings and measurement of any 
injection site erythema or swelling/induration reported on the following day may be excluded 
from the analyses of solicited ARs. 
Any new safety information reported during safety telephone calls or at site visits (including a 
solicited AR) that is not already captured in the eDiary will be described in the source documents 
as a verbally reported event. Any AR reported in this manner must be described as an unsolicited 
event and therefore entered on the AE eCRF. 

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Study site staff will review eDiary data with participants during the safety call 7 days after 
vaccination. 
The eDiary will also be used every 2 weeks from Day 36 to Day 162 and from Day 202 to 
Day 342 to capture the occurrence of MAAEs, AESIs, SAEs, or AEs leading to withdrawal. The 
eDiary will prompt the participant to complete an eDiary questionnaire that collects the 
following data: 
• Changes in health since last completing the questionnaire or since in contact with the 
study site 
• Known exposure to someone with known COVID-19 or SARS-CoV-2 infection 
• Any experience of symptoms of COVID-19 
• Any MAAEs, AESIs, or SAEs 
If an eDiary record results in identification of relevant safety events according to the study 
period or of symptoms of COVID-19, a follow-up safety call will be triggered. 
Apart from the safety telephone calls described in Section 7.3.2 at Day 8 and every 2 weeks 
starting from Day 43 to Day 169 and from Day 209 to Day 349, each participant will complete a 
questionnaire in an eDiary for Day 36 to Day 162 and from Day 202 to Day 342 (Table 8). The 
eDiary responses will be reviewed by study site personnel and may result in a follow-up safety 
call by the site to the participant. 
7.3.1.1. 
Ancillary Supplies for Participant Use 
Study sites will distribute Sponsor-provided oral thermometers and rulers for use by participants 
to assess body temperature and injection site reactions, respectively, for recording solicited ARs 
in the eDiaries. Based on availability, smartphone devices may be provided to those participants 
who do not have their own device to use for eDiary activities. 
7.3.2. 
Safety Telephone Call 
A safety telephone call is a telephone call made to the participant by trained site personnel. This 
call will follow an approved script, which will facilitate the collection of relevant safety 
information. There will be a safety telephone call on Day 8 for each participant to discuss their 
health and review their eDiary. Safety calls by the site to each participant will occur on Day 8 
and every 2 weeks from Day 43 to Day 169 and from Day 209 to Day 349 (Table 8). The 
participant will be interviewed according to the script about the occurrence of AEs, MAAEs, 
AESIs, AEs leading to withdrawal, SAEs, concomitant medications associated with those events, 
and any nonstudy vaccinations temporally associated with these events (Section 7.4.7). In 
addition, study personnel will collect information on known participant exposure to someone 

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with COVID-19 or SARS-CoV-2 infection and on the participant’s experience of COVID-19 
symptoms. All safety information collected from the telephone call must be documented in the 
source documents as described by the participant and not documented on the script used for the 
safety telephone contact. As noted in Section 7.3.1, an unscheduled follow-up safety call may be 
triggered if an eDiary record results in identification of a relevant safety event. 
7.3.3. 
Laboratory Assessments 
No routine safety laboratory assessments are planned for this study. 
A point-of-care urine pregnancy test will be performed at Day 1 before vaccination. At any time, 
a pregnancy test either via blood or point-of-care urine can be performed, at the discretion of the 
investigator. If postmenopausal status is not documented in a female participant’s medical 
records, an FSH test to confirm may be performed at the Screening Visit, as necessary and at the 
discretion of the investigator, to confirm postmenopausal status. 
7.3.4. 
Vital Sign Measurements 
Vital sign measurements will include systolic and diastolic blood pressure, heart rate, respiratory 
rate, and body temperature (preferred route is oral). The participant will be seated for at least 
5 minutes before all measurements are taken. Vital signs will be measured at the time points 
indicated in the SoE (Table 8). Vital signs are to be collected pre- and post-vaccination on the 
day of injection (Day 1) only. When applicable, vital sign measurements should be performed 
before blood collection. 
Participants who are febrile (body temperature ≥ 38.0°C/100.4°F) before injection on Day 1 must 
be rescheduled within the relevant window period to receive the injection. Afebrile participants 
with minor illnesses may be vaccinated at the discretion of the investigator. 
7.3.5. 
Physical Examinations 
A full physical examination, including height and weight, will be performed at Day 1 as 
indicated in the SoE (Table 8). The full examination will include assessment of skin, head, ears, 
eyes, nose, throat, neck, thyroid, lungs, heart, cardiovascular system, abdomen, lymph nodes, and 
musculoskeletal system and extremities. Any clinically significant finding identified during a 
study visit should be reported as an MAAE. 
Symptom-directed physical examinations may be performed at other time points at the discretion 
of the investigator. On the day of vaccination, before injection, the arm receiving the injection 
should be examined and the associated lymph nodes should be evaluated. 

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7.3.6. 
Assessment for SARS-CoV-2 Infection 
Participants will have NP samples collected for SARS-CoV-2 testing at time points specified in 
the SoE (Table 8). 
A study illness visit or a consultation will be arranged within 24 hours or as soon as possible to 
collect an NP swab (Table 8, Unscheduled Visit [UNS]) to ascertain the presence of 
SARS-CoV-2 via RT-PCR if a participant experiences any of the following (the presence of any 
one of these symptoms lasting at least 48 hours [except for fever and/or respiratory symptoms]): 
• Signs or symptoms of SARS-CoV-2 infection as defined by the CDC (CDCb 2021), 
including:  
o Fever (temperature ≥ 38.0°C [100.4°F]) or chills (of any duration, including 
≤ 48 hours) 
o Cough (of any duration, including ≤ 48 hours) 
o Shortness of breath and/or difficulty breathing (of any duration, including 
≤ 48 hours) 
o Fatigue 
o Muscle or body aches 
o Headache 
o New loss of taste and/or smell 
o Sore throat, congestion, or runny nose 
o Nausea or vomiting 
o Diarrhea 
• MAAE suggesting a SARS-CoV-2 infection 
• Clinical or radiographical evidence of pneumonia 
Additionally, clinical information will be carefully collected to evaluate the severity of the 
clinical case. All findings will be recorded in the eCRF. 
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 or mRNA-1283 (eg, myalgia, 
headache, fever, and chills). During the first 7 days after vaccination, when these solicited ARs 
are common, investigators should use their clinical judgment to decide whether an NP swab 
should be collected. The collection of an NP swab prior to the Day 1 vaccination can help ensure 

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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. 
If scheduled, a study site illness visit may include additional assessments such as medical 
history, physical examination, and blood sampling for clinical laboratory testing. The NP swab 
sample may be tested by multiplex RT-PCR for respiratory viruses besides SARS-CoV-2 to 
evaluate the severity of the clinical case. Radiologic imaging studies may be conducted. Blood 
samples will be collected at all illness visits for potential future immunologic assessment of 
SARS-CoV-2 infection. 
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 visit will also be 
considered cases, assuming that the symptomology criteria for COVID-19 are met and a 
respiratory sample is positive for SARS-CoV-2 by PCR at a Clinical Laboratory Improvement 
Amendments (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. 
Symptomatic COVID-19 is defined by the presence of one of the CDC-listed symptoms 
(CDC 2021b) and a positive RT-PCR test on a respiratory sample. Asymptomatic SARS-CoV-2 
infection is defined as a positive RT-PCR test on a respiratory sample in the absence of 
symptoms or a positive serologic test for anti-nucleocapsid antibody after a negative test result at 
the time of enrollment, with the serologic assay detecting previously resolved SARS-CoV-2 
infections that may have occurred between visits, and the RT-PCR to detect active viral infection 
at the time of a visit. If participants are confirmed to have SARS-CoV-2 infection and are 
symptomatic or asymptomatic, the investigator will notify the participants’ primary care 
physicians of the diagnosis and the local public health authorities as required per local 
regulations. 
If the participant had known exposure to COVID-19 (eg, exposure to someone with a confirmed 
case of COVID-19), it will be captured in the COVID-19 exposure form, and the participant will 
continue to follow all remaining study assessments as scheduled. Likewise, participants with a 
confirmed case of COVID-19 will continue to follow all remaining study assessments as 
scheduled. 
Any confirmed symptomatic COVID-19 infection occurring in participants will be captured as 
an MAAE along with relevant concomitant medications and details about severity, seriousness, 
and outcome. 

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7.4. 
Safety Definitions and Related Procedures 
7.4.1. 
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. 
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 vaccination even though they may have 
been present before the start of the study. 
Events NOT Meeting the Adverse Event Definition 
• Procedures planned before study entry (eg, hospitalization for preplanned surgical 
procedure). 
• 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 vaccine caused the AE 
(Section 7.4.3). For the purposes of investigational new drug safety reporting, “reasonable 
possibility” means that there is evidence to suggest a causal relationship between the vaccine 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 but starts outside the protocol-defined period for 
reporting solicited ARs (ie, 7 days after vaccination). 
7.4.2. 
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 the IP. 
• Is life-threatening  
An AE is considered life-threatening if, in the view of either the investigator or the 

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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 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. 
7.4.3. 
Solicited Adverse Reactions 
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 7.3.1). Participants will record such occurrences in an 
eDiary during the 7 days after vaccination (ie, the day of injection and 6 subsequent days).  

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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 Preventive Vaccine Clinical 
Trials (DHHS 2007). 
If a solicited local or systemic AR continues beyond 7 days after vaccination, 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 study staff 
either via phone call or at the next study visit. All solicited ARs (local and systemic) will be 
considered causally related to vaccination. 
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 

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Reaction 
Grade 0 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
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 
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 
Note: Events listed above but starting > 7 days after study injection will be recorded on the AE CRF. Causality for each event 
will be determined per assessment by the investigator. 
Any solicited AR that meets any of the following criteria must be entered into the participant’s 
source document and must also be recorded by the study site staff on the solicited AR page of the 
participant’s eCRF: 
• Solicited local or systemic AR that results in a visit to a healthcare practitioner 
(HCP), to be recorded as an MAAE (Section 7.4.4) 
• 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) 

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• Solicited local or systemic AR lasting beyond 7 days post-injection 
• Solicited local or systemic AR that otherwise meets the definition of an SAE 
7.4.4. 
Medically Attended Adverse Events 
An MAAE is an AE that leads to an unscheduled visit to an HCP. This would include visits to a 
study site for unscheduled assessments (eg, abnormal laboratory follow-up, COVID-19 
[Section 7.3.6]) 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. 
Unsolicited AEs will be captured on the AE page of the eCRF. 
All confirmed COVID-19 cases will be recorded as MAAEs. 
All suspected cases of anaphylaxis should be recorded as MAAEs and reported as an SAE, based 
on the 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 per Section 7.4.11. 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 or symptoms consistent with anaphylaxis (as follows) 
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 multiorgan 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 the following: 
• Sudden onset AND 
• Rapid progression of signs and symptoms AND 
• Involves 2 or more organ systems, as follows: 
− Skin/mucosal: urticaria (hives), generalized erythema, angioedema, generalized 
pruritus with skin rash, generalized prickle sensation, and red and itchy eyes. 
− Cardiovascular: measured hypotension, clinical diagnosis of uncompensated 
shock, loss of consciousness or decreased level of consciousness, and evidence of 
reduced peripheral circulation. 
− Respiratory: bilateral wheeze (bronchospasm), difficulty breathing, stridor, 
upper airway swelling (lip, tongue, throat, uvula, or larynx), respiratory distress, 

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persistent dry cough, hoarse voice, sensation of throat closure, sneezing, and 
rhinorrhea. 
− Gastrointestinal: diarrhea, abdominal pain, nausea, and vomiting. 
7.4.5. 
Adverse Event of Special Interest  
An AESI is an AE (serious or nonserious) 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. Such events may require further investigation to 
characterize and understand them. Section 10.4 (Appendix 4) provides a list of AESIs pertinent 
to vaccine mRNA-1273. All AESIs will be collected through the entire 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 (EDC) 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 7.4.11). 
7.4.5.1. 
Myocarditis and/or Pericarditis 
Very rare events of myocarditis and/or pericarditis have been reported after vaccination with the 
mRNA-1273 vaccine. 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 7.4.11. 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, any event suspicious for myocarditis, 
pericarditis, or myopericarditis should be reported as an AESI. The CDC case definition is 
displayed below as guidance (Gargano et al 2021). However, any suspected case should be 
reported, even if it does not fulfil the criteria to be identified as a probable or confirmed case of 
acute myocarditis, or as a case of acute pericarditis. These definitions are intended to serve as a 
guide to help reporting of suspected cases of myocarditis, pericarditis, or myopericarditis, but the 
diagnosis of suspected cases are left to the investigator's clinical judgment.  
7.4.5.2. 
Acute Myocarditis Case Definition 
Presence of ≥ 1 new or worsening of the following clinical symptoms: 
• Chest pain/pressure/discomfort 
• Dyspnea/shortness of breath/pain with breathing 
• Palpitations 

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• Syncope 
AND 
For probable case: 
≥ 1 new finding of: 
• Troponin level above upper limit of normal (any type of troponin) 
• Abnormal electrocardiogram (ECG or EKG) or rhythm monitoring findings 
consistent with myocarditis 
− To meet the ECG or rhythm monitoring criterion, a probable case must include at 
least one of: 
− 
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 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 
7.4.5.3. 
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 

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• New ST-elevation or PR-depression on EKG 
• New or worsening pericardial effusion on echocardiogram or cMRI 
7.4.5.4. 
Case Definition of Myopericarditis 
Participants who meet criteria for both myocarditis and pericarditis may be described under 
myopericarditis. 
An independent cardiac event adjudication committee (CEAC) that includes pediatric and adult 
cardiologists will review any suspect 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, which will then make a final decision 
on whether to suspend further enrollment and/or study vaccination based on 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. 
7.4.6. 
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 at any time during the study should receive no 
further vaccination with IP but should be asked to remain in the study and be monitored for 
safety. 
Details of all pregnancies in female participants will be collected after the start of study 
treatment and until the end of their participation in the study. 
• 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) will be 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, using the SAE Mailbox, the SAE Hotline, 
or the SAE Fax line (Section 7.4.11). 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 

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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. 
7.4.7. 
Eliciting and Documenting Adverse Events 
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 vaccination. Other (unsolicited) 
AEs will be collected from Day 1 through 28 days after vaccination. 
The MAAEs, AESIs, AEs leading to withdrawal, and SAEs will be collected from participants as 
specified in the SoE (Table 8) until the end of their participation in the study. Any AEs occurring 
before receipt of IP will be analyzed separately from AEs occurring after receipt of the study 
vaccine. 
At every study site visit or telephone contact, participants will be asked a standard question to 
elicit any medically related changes in their well-being (including COVID-19 symptoms) 
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 nonstudy 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 6.3). 
7.4.8. 
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 7.4.2), NOT when it is rated as severe. 
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 Preventive 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 7.4.3. 

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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. 
7.4.9. 
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. 
7.4.10. 
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 

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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 of screening 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. 
7.4.11. 
Reporting SAEs 
Prompt notification by the investigator to the Sponsor of an SAE is essential so that legal 
obligations and ethical responsibilities toward the safety of participants and the safety of a study 
intervention under clinical investigation are met. 
Any AE considered serious by the investigator or that meets SAE criteria (Section 7.4.2) must be 
reported to the Sponsor immediately (within 24 hours of becoming aware of the SAE) via the 
EDC system. 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 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 
Regulatory reporting requirements for SAEs are described in Section 7.4.15. 
The investigator and any qualified designees are responsible for detecting, documenting, and 
recording events that meet the definition of an AE, including SAEs, and remain responsible for 
following up AEs that are serious, considered related to IP or study procedures, or that caused 
the participant to discontinue the study. 
Any SAE occurring after the EoS and considered to be caused by the study vaccine must be 
reported to the Sponsor. 

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7.4.12. 
Time Period and Frequency for Collecting AE, AESI, and SAE Information 
Medical occurrences that begin before IP administration but after obtaining informed consent 
will be recorded in the Medical History/Current Medical Conditions section of the eCRF and not 
in the AE section; however, if the condition worsens at any time during the study, it will be 
recorded and reported as an AE. 
Adverse events may be collected as follows: 
• Observing the participant 
• Receiving an unsolicited complaint from the participant 
• Questioning the participant in an unbiased and nonleading manner 
Solicited AEs will be collected from the day of injection through 6 days after vaccination. Other 
(unsolicited) AEs will be collected from the day of injection through 28 days after vaccination. 
Serious AEs (including AESIs) will be collected from the start of IP administration until the last 
day of study participation. 
All SAEs and AESIs will be recorded and reported to the Sponsor or designee immediately and 
under no circumstance should this exceed 24 hours of becoming aware of the event via the EDC 
system. If a site receives a report of a new SAE or AESI from a study participant or receives 
updated data on a previously reported SAE or AESI and the eCRF has been taken offline, then 
the site can report this information on a paper SAE or AESI form using the SAE Mailbox, the 
SAE Hotline, or the SAE Fax line (Section 7.4.11). 
An abnormal value or result from a clinical or laboratory evaluation can also indicate an AE if it 
is determined by the investigator to be clinically significant (eg, leads to study drug 
discontinuation or meets any serious criteria). If this is the case, it must be recorded in the source 
document and as an AE on the appropriate AE form(s). The evaluation that produced the value 
or result should be repeated until that value or result returns to normal or is stabilized and the 
participant’s safety is not at risk. 
Investigators are not obligated to actively seek AEs or SAEs after EoS participation. However, if 
the investigator learns of any SAE (including a death) at any time after a participant has 
withdrawn from or completed the study, and the investigator considers the event to be reasonably 
related to the IP or study participation, the investigator must promptly notify the Sponsor. 
7.4.13. 
Method of Detecting AEs and SAEs 
Electronic diaries have specifically been designed for this study by the Sponsor. The diaries will 
include prelisted AEs (solicited ARs) and intensity scales; they will also include blank space for 

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the recording of information on other AEs (unsolicited AEs) and concomitant 
medications/vaccinations. 
The investigator is responsible for the documentation of AEs regardless of treatment group or 
suspected causal relationship to IP. For all AEs, the investigator must pursue and obtain 
information adequate to determine the outcome of the AE and to assess whether the AE meets 
the criteria for classification as an SAE requiring immediate notification to the Sponsor or its 
designated representative. 
Care will be taken not to introduce bias when detecting AEs and/or SAEs. Open-ended and 
nonleading verbal questioning of the participant is the preferred method to inquire about 
AE occurrences. 
7.4.14. 
Follow-up of AEs and SAEs 
After the initial AE/SAE report, the investigator is required to proactively follow each participant 
at subsequent visits and 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 6.3. 
7.4.15. 
Regulatory Reporting Requirements for SAEs 
• Prompt notification by the investigator to the Sponsor of an SAE is essential so that 
legal obligations and ethical responsibilities toward 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 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 an 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, if appropriate 
according to local requirements. 

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7.5. 
Safety Monitoring 
Safety monitoring for this study will include an unblinded DSMB. 
Blinded safety monitoring for this study will include study team members, inclusive of, at a 
minimum, the Sponsor medical monitor, Sponsor safety physician (from Pharmacovigilance), 
and CRO medical monitor. The study team will conduct ongoing safety reviews during the study 
and will be responsible to monitor for safety concerns during the study as described in the Safety 
Management Plan. 
An independent 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. 
7.6. 
Treatment 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 10.2.8). 
7.7. 
Pharmacokinetics 
Pharmacokinetic parameters are not evaluated in this study. 
7.8. 
Pharmacodynamics  
Pharmacodynamic parameters are not evaluated in this study. 
7.9. 
Biomarkers 
Immunogenicity assessments are described in Section 7.1. Biomarkers are not evaluated in this 
study. 
7.10. 
Health Economics 
Health economics are not evaluated in this study. 

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8. 
STATISTICAL ANALYSIS PLAN 
This section summarizes the planned statistical analysis strategy and procedures for the study. 
The details of statistical analysis will be provided in the statistical analysis plan (SAP), which 
will be finalized before the clinical database lock for the study. If changes are made to primary 
and/or key secondary objectives or the related statistical methods after the study has begun, 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. 
8.1. 
Blinding and Responsibility for Analyses 
Blinding during the study will be conducted as described in Section 5.2. The Sponsor 
Biostatistics Department or designee will generate the randomized allocation schedule(s) for 
study treatment assignment. Randomization will be implemented via an IRT. 
Participant-level unblinding at the time of the primary analysis will be restricted to an 
independent unblinded statistician and, as needed, a statistical programmer who will perform the 
primary analysis, who will have no other responsibilities associated with the study. 
The planned study analyses are described in Section 8.6. 
8.2. 
Statistical Hypotheses 
No formal hypotheses will be tested. 
8.3. 
Sample Size Determination 
The sample size for this trial is not driven by statistical assumptions for formal hypothesis testing. 
The number of proposed participants is considered sufficient to provide a descriptive summary of 
the safety and immunogenicity of each treatment group. In Part A, up to 420 participants will be 
randomized to 6 treatment arms in a 1:1:1:1:1:1 ratio to mRNA-1283 at three dose levels, 
mRNA-1283.211 at two dose levels, and mRNA-1273 at a single dose level, respectively (ie, up 
to 70 participants for each treatment group). In Part B, up to 140 participants will be enrolled in a 
1:1 ratio to mRNA-1283.529 at two dose levels (ie, up to 70 participants for each treatment group). 
Enrollment in both parts of this study will be stratified by age with two age strata: 18-55 years of 
age and ≥ 56 years of age, with at least 20% but not more than 50% of participants 56 years of age 
or older. 
8.4. 
Analysis Sets 
The analysis sets are described in Table 6. 

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Table 6: Analysis Sets (same definition across part A and B if applicable) 
Set 
Description 
Randomization Analysis Set 
(Part A) 
The Randomization Analysis Set consists of all participants who are 
randomized. Randomization Analysis Set is applicable to Part A only. 
Full Analysis Set (FAS) 
The FAS consists of all randomized/enrolled (Part A: randomized, 
Part B: enrolled) participants who receive one dose of IP. 
Per-Protocol (PP) Set for 
Immunogenicity 
The PP Set for Immunogenicity consists of all participants in the FAS 
who receive the planned dose of IP and who have no major protocol 
deviations that impact key or critical data. 
The PP Set for Immunogenicity will be used as the primary analysis 
set for analyses of immunogenicity unless otherwise specified. 
Safety Set 
The Safety Set consists of all randomized/enrolled (Part A: 
randomized, Part B: enrolled) participants who receive 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. 
Solicited Safety Set 
The Solicited Safety Set consists of all participants in the Safety Set 
who contribute any solicited AR data. 
The Solicited Safety Set will be used for the analyses of solicited 
ARs. Participants will be included in the treatment group 
corresponding to the IP that they actually received. 
8.5. 
Statistical Methods 
8.5.1. 
Baseline Characteristics and Demographics 
Part A and B: 
Demographic variables (eg, age, gender, race, ethnicity, height, weight, and body mass index) 
and baseline characteristics will be summarized by treatment group and overall. Summary 
statistics (mean, standard deviation for continuous variable, and number and percentage for 
categorical variables) will be provided. 
8.5.2. 
Efficacy Analysis 
Part A and B: 
No pre-specified efficacy analysis will be performed. Exploratory analyses of symptomatic and 
asymptomatic SARS-CoV-2 infection by treatment group may be performed. 
8.5.3. 
Safety Analyses 
Part A and B: 

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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. Participants will be included in the treatment group corresponding to the IP that they 
actually received. 
Safety and reactogenicity will be assessed by clinical review of all relevant parameters, including 
solicited ARs (local and systemic ARs), unsolicited AEs, treatment-related AEs, severe AEs, 
SAEs, MAAEs, AESIs, and AEs leading to withdrawal from study participation. 
The number and percentage of participants with any solicited local AR, with any solicited 
systemic AR, with any solicited AR during the 7-day follow-up period after the single dose, and 
with Grade 3 or higher solicited AR will be provided. A 2-sided 95% exact CI using the 
Clopper-Pearson method will also be provided for the percentage of participants with any 
solicited AR for each treatment group. 
The number and percentage of participants with unsolicited AEs, treatment-related AEs, severe 
AEs, SAEs, MAAEs, AESIs, and AEs leading to withdrawal from study participation will be 
summarized. Unsolicited AEs will be presented by MedDRA system organ class and preferred 
term. Unsolicited AEs will be coded according to the MedDRA Dictionary for Adverse Reaction 
Terminology. 
The number of events of solicited ARs, unsolicited AEs, SAEs, MAAEs, AESIs, and AEs 
leading to withdrawal will be reported in summary tables accordingly. Vital signs and physical 
examination findings will be summarized. Pregnancy outcomes will also be summarized. 
 
 

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Table 7 summarizes the analysis strategy for safety parameters. For all other safety parameters, 
descriptive summary statistics will be provided. Further details will be described in the SAP. 
 
 

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Table 7: Analysis Strategy for Safety Parameters 
Safety Endpoint 
Number and Percentage of 
Participants, Number of Events 
95% CI for Each 
Treatment Group 
Any Solicited AR (overall and by local, systemic) 
X 
X 
Any Unsolicited AE 
X 
— 
Any SAE 
X 
— 
Any Unsolicited MAAE 
X 
— 
Any Unsolicited AESI 
X 
— 
Any Unsolicited Treatment-Related AE 
X 
— 
Any Treatment-Related SAE 
X 
— 
Any Unsolicited AE Leading to Withdrawal from 
Study Participation 
X 
— 
Any Severe Unsolicited AE 
X 
— 
Any Treatment-Related Severe Unsolicited AE 
X 
— 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; CI = confidence interval; 
MAAE = medically attended adverse event; SAE = serious adverse event. 
Notes: 95% CI using the Clopper-Pearson method, X = results will be provided. 
8.5.4. 
Immunogenicity Analyses 
Immunogenicity analyses will be performed based on the PP Set for Immunogenicity and 
provided by treatment group. 
8.5.4.1. 
Analysis for the Primary Immunogenicity Objective 
Part A: 
For the primary immunogenicity endpoints of levels of SARS-CoV-2–specific nAb and 
SARS-CoV-2–specific bAb against the SARS-CoV-2 prototype virus strain and against the 
variant strains including B.1.351, immune response of each treatment group will be assessed 
with respect to the mRNA-1273 
 booster dose. An analysis of covariance (ANCOVA) 
model will be employed to compare immune response between each treatment group against the 
mRNA-1273 
 booster dose. Day 29 antibody titers (against prototype virus strain or the 
variant strain) will be included in the model as a dependent variable and treatment group variable 
(mRNA-1283 at each dose level, mRNA-1283.211 at each dose level, and mRNA-1273 
) 
will be included as fixed effect. The model will also adjust for age group (< 56, ≥ 56). The 
geometric mean titer (GMT) will be estimated by the geometric least square mean (GLSM) from 
the model for each group and corresponding 95% CI will be provided. The ratio of GMTs for 
each treatment group with respect to the mRNA-1273 
 booster dose will be estimated by 
the ratio of GLSM from the model. The 95% CI for the ratio of GLSM will be provided to assess 
CCI
CCI
CCI
CCI

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the between-groups difference (each treatment group against mRNA-1273 
 booster dose) in 
immune response against the prototype strain (or variant strain). 
The primary immunogenicity endpoints of the study will also be assessed by the vaccine 
seroresponse (definition to be provided in the SAP) against the SARS-CoV-2 prototype virus 
strain and against variant strains including B.1.351. The seroresponse rate (SRR) with 95% CI at 
Day 29 will be summarized for each treatment group. The difference of SRRs and 95% CI at 
Day 29 will be calculated for mRNA-1283 at each dose level and mRNA-1283.211 at each dose 
level compared with mRNA-1273. 
Part B: 
The same analysis methods will be used to analyzed immunogenicity data for Part B. An 
ANCOVA model will be used to compare immune response between treatment group (
 
mRNA-1283.529) in Part B. Day 29 antibody titers against B.1.1.529 will be included in the 
model as a dependent variable and treatment group variable (mRNA-1283.529  at each dose 
level) will be included as fixed effect. The model will also adjust for age group (< 56, ≥ 56). The 
GMT will be estimated by the GLSM from the model for each group and corresponding 95% CI 
will be provided. The ratio of GMTs for 
 mRNA-1283.529 with respect to 
 
mRNA-1283.529 booster dose will be estimated by the ratio of GLSM from the model. The 95% 
CI for the ratio of GLSM will be provided to assess the between-groups difference in immune 
response against B.1.1.529. 
SRR against B.1.1.529 with 95% CI at Day 29 will be summarized for each mRNA-1283.529 
dose level The difference of SRRs and 95% CI at Day 29 between two dose levels will also be 
calculated. 
8.5.4.2. 
Analysis for the Secondary and Exploratory Immunogenicity Objectives 
Part A and B: 
Immunogenicity, SARS-CoV-2–specific bAb and nAb, will be assessed at multiple time points 
in this study; however, Day 29, 28 days after booster dose, is the time point of primary interest. 
For each of the antibodies of interest, eg, levels of SARS-CoV-2–specific bAb and 
SARS-CoV-2–specific nAb, the GMT or level with corresponding 95% CI at each time point 
and geometric mean fold rise (GMFR) of post-baseline/baseline titers or levels with 
corresponding 95% CI at each post-baseline time point will be provided by treatment group. The 
95% CIs will be calculated based on the t-distribution of the log-transformed values, then 
back-transformed to the original scale for presentation. The following descriptive statistics will 
also be provided at each time point: number of participants (n), median, minimum, and 
maximum. 
CCI
CCI
CCI
CCI

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The SRR of each treatment group against the prototype strain and variant strain, defined as the 
percentage of participants achieving seroresponse against the prototype strain and variant strain, 
respectively, will be provided for each treatment group with the 95% CI calculated using the 
Clopper-Pearson method at each post-baseline time point. 
8.5.5. 
Subgroup Analyses 
Part A and B: 
Subgroup analyses may include age and SARS-CoV-2 infection status at baseline depending on 
the sample size in a subgroup. Details will be provided in the SAP. 
8.6. 
Planned Analyses 
8.6.1. 
Primary Analysis 
The primary analysis of safety and immunogenicity will be conducted after Part A participants 
have completed their Day 29 visit assessments. The primary analysis will be performed by a 
separate team of unblinded programmers and statisticians. The analysis, including any cases of 
COVID-19, will be presented by treatment group. With the exception of appropriately delegated 
unblinded study staff, vaccine administrators, and monitors, all personnel involved in the 
conduct of the trial will remain blinded to individual treatment assignment until unblinding. 
Investigators will be blinded until after the final database lock for final analysis. The protocol 
may be amended to further assess or confirm dose selection based on results of this analysis. 
8.6.2. 
Interim Analysis 
The interim analysis of safety and immunogenicity will be conducted after Part B participants 
have completed their Day 29 visit assessments. The interim analysis will be performed by study 
team programmers and statisticians.  
8.6.3. 
Final Analysis 
The final analysis of all endpoints will be performed after all participants (Part A and Part B) 
have completed all planned study procedures. Results of this analysis will be presented in a final 
CSR, including individual listings. The final CSR will include full analyses of all safety and 
immunogenicity data through Day 366 (Month 12). 

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9. 
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Chen WH, Tao X, Agrawal AS, Algaissi A, Peng B-H, Pollet J, et al. Yeast-expressed 
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Review Boards: Conduct of clinical trials of medical products during the COVID-19 public 
health emergency. January 27, 2021 [cited 2021 Aug 20] [38 screens]. Available from: 
https://www.fda.gov/media/136238/download. 
Department of Health and Human Services (DHHS), Food and Drug Administration, Center for 
Biologics Evaluation and Research (US). Guidance for Industry: Toxicity grading scale for 
healthy adult and adolescent volunteers enrolled in preventive vaccine clinical trials. September 
2007 [cited 2020 Oct 28] [10 screens]. Available from: 
https://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInfor
mation/Guidances/Vaccines/ucm091977.pdf. 
Ferreira VM, Schulz-Menger J, Holmvang G, Kramer CM, Carbone I, Sechtem U, et al. 
Cardiovascular magnetic resonance in nonischemic myocardial inflammation: expert 
recommendations. J Am Coll Cardiol. 2018 Dec 18;72(24):3158-76. 
Gargano JW, Wallace M, Hadler SC, Langley G, Su JR, Oster ME, et al. Use of mRNA 
COVID-19 vaccine after reports of myocarditis among vaccine recipients: update from the 
advisory committee on immunization practices - United States, June 2021. MMWR Morb Mortal 
Wkly Rep. 2021 Jul 9;70(27):977-82. 
Greaney AJ, Loes AN, Crawford KHD, Starr TN, Malone KD, Chu HY, et al. Comprehensive 
mapping of mutations to the SARS-CoV-2 receptor-binding domain that affect recognition by 
polyclonal human plasma antibodies. Cell Host Microbe. 2021 Mar 10;29(3):463-76.e6. 
Liu L, Wang P, Nair MS, Yu J, Rapp M, Wang Q, et al. Potent neutralizing antibodies against 
multiple epitopes on SARS-CoV-2 spike. Nature. 2020 Aug;584(7821):450-6. 
Lv Z, Deng Y-Q, Ye Q, Cao L, Sun C-Y, Fan C, et al. Structural basis for neutralization of 
SARS-CoV-2 and SARS-CoV by a potent therapeutic antibody. Science. 2020 Sep 
18;369(6510):1505-9. 
Madhi SA, Baillie V, Cutland CL, Voysey M, Koen AL, Fairlie L, et al; NGS-SA Group; Wits–
VIDA COVID Group. Efficacy of the ChAdOx1 nCoV-19 Covid-19 vaccine against the B.1.351 
variant. N Engl J Med. 2021 May;384(20):1885-98. 
Martin MA, VanInsberghe D, Koelle K. Insights from SARS-CoV-2 sequences. Science. 2021 
Jan 29;371(6528):466-7. 
Rüggeberg JU, Gold MS, Bayas J-M, Blum MD, Bonhoeffer J, Friedlander S, et al; Brighton 
Collaboration Anaphylaxis Working Group. Anaphylaxis: case definition and guidelines for data 
collection, analysis, and presentation of immunization safety data. Vaccine. 2007 Aug 
1;25(31):5675-84. 

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Shinde V, Bhikha S, Hoosain Z, Archary M, Bhorat Q, Fairlie L, et al; 2019nCoV-501 Study 
Group. Efficacy of NVX-CoV2373 Covid-19 vaccine against the B.1.351 variant. N Engl J Med. 
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vaccine-elicited antibodies to SARS-CoV-2 and circulating variants. bioRxiv [Preprint]. 2021; 
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Geneva, Switzerland: WHO; 2021 Aug 10 [cited 2021 Aug 20]. Available from: 
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neutralizing activity elicited by mRNA-1273 vaccine. N Engl J Med. 2021 Apr 15;384(15):1468-
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protein of SARS-CoV-2 induces protective immunity. Nature. 2020 Oct;586(7830):572-7. 
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a postmarketing surveillance review. Eur J Pediatr. 2002 Jan;161(1):21-5. 

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10. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 

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10.1. 
APPENDIX 1: Schedule of Events  
Table 8: Schedule of Events for Part A and Part B 
Visit Number 
Screening1 
V11 
 
V2 
V3 
V4 
 
 
V5 
 
 
V6 
UNS 
Type of Visit 
C 
C 
SC 
C 
C 
C 
SFU 
SFU 
C 
SFU 
SFU 
C 
C 
Month Time Point 
M0 
M0 
 
 
M1 
M3 
eDiary 
SC 
M6 
eDiary 
SC 
M12 
-- 
Study Visit Day  
Screening1 
D11 
D8 
D15 
D29 
D90 
Every 2 
weeks 
D36-D1622 
Every 2 
weeks 
D43-D169 
D181 
Every 2 
weeks 
D202-D3422 
Every 2 
weeks 
D209- 
D349 
D366 
 
Window Allowance 
(Days) 
-7 
0 
+3 
±3 
-7 to +3 
±7 
±2 
±3 
±14 
±2 
±3 
±14 
-- 
Days Since Most 
Recent Injection 
 
0 
7 
14 
28 
89 
-- 
 
180 
-- 
 
365 
-- 
Informed consent 
form, demographics, 
concomitant 
medications, medical 
history 
X 
 
 
 
 
 
 
 
 
 
 
 
 
Study injection 
(including 30-minute 
post-vaccination 
observation period) 
 
X 
 
 
 
 
 
 
 
 
 
 
 
Confirm participant 
meets inclusion and 
exclusion criteria 
X 
X 
 
 
 
 
 
 
 
 
 
 
 
Physical examination 
including vital signs3 
X 
X 
 
 
X 
 
 
 
X 
 
 
X 
X 
Pregnancy testing 
 
X 
 
 
 
 
 
 
 
 
 
 
 

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Visit Number 
Screening1 
V11 
 
V2 
V3 
V4 
 
 
V5 
 
 
V6 
UNS 
Type of Visit 
C 
C 
SC 
C 
C 
C 
SFU 
SFU 
C 
SFU 
SFU 
C 
C 
Month Time Point 
M0 
M0 
 
 
M1 
M3 
eDiary 
SC 
M6 
eDiary 
SC 
M12 
-- 
Study Visit Day  
Screening1 
D11 
D8 
D15 
D29 
D90 
Every 2 
weeks 
D36-D1622 
Every 2 
weeks 
D43-D169 
D181 
Every 2 
weeks 
D202-D3422 
Every 2 
weeks 
D209- 
D349 
D366 
 
Window Allowance 
(Days) 
-7 
0 
+3 
±3 
-7 to +3 
±7 
±2 
±3 
±14 
±2 
±3 
±14 
-- 
Days Since Most 
Recent Injection 
 
0 
7 
14 
28 
89 
-- 
 
180 
-- 
 
365 
-- 
Blood for 
SARS-CoV-2 
serology 
(anti-nucleocapsid 
antibody) 
 
X 
 
 
X 
X 
 
 
X 
 
 
X 
X 
Blood for humoral 
immunogenicity4 
 
X 
 
X 
X 
X 
 
 
X 
 
 
X 
X 
Blood (PBMCs) for 
cellular 
immunogenicity 
 
X 
 
 
X 
 
 
 
X 
 
 
X 
 
Nasopharyngeal swab 
sample for 
SARS-CoV-25 
 
X 
 
 
X 
X 
 
 
X 
 
 
X 
X 
eDiary activation for 
recording solicited 
adverse reactions (7 
days) 
 
X 
 
 
 
 
 
 
 
 
 
 
 
Review of eDiary 
 
 
X 
 
 
 
X 
 
 
X 
 
 
 
Follow-up safety 
calls6 
 
 
X 
 
 
 
 
X 
 
 
X 
 
 

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Visit Number 
Screening1 
V11 
 
V2 
V3 
V4 
 
 
V5 
 
 
V6 
UNS 
Type of Visit 
C 
C 
SC 
C 
C 
C 
SFU 
SFU 
C 
SFU 
SFU 
C 
C 
Month Time Point 
M0 
M0 
 
 
M1 
M3 
eDiary 
SC 
M6 
eDiary 
SC 
M12 
-- 
Study Visit Day  
Screening1 
D11 
D8 
D15 
D29 
D90 
Every 2 
weeks 
D36-D1622 
Every 2 
weeks 
D43-D169 
D181 
Every 2 
weeks 
D202-D3422 
Every 2 
weeks 
D209- 
D349 
D366 
 
Window Allowance 
(Days) 
-7 
0 
+3 
±3 
-7 to +3 
±7 
±2 
±3 
±14 
±2 
±3 
±14 
-- 
Days Since Most 
Recent Injection 
 
0 
7 
14 
28 
89 
-- 
 
180 
-- 
 
365 
-- 
Recording of 
unsolicited AEs 
 
X 
X 
X 
X 
 
 
 
 
 
 
 
 
Recording of 
MAAEs, SAEs, and 
AESIs and 
concomitant 
medications relevant 
to or for the treatment 
of these AEs7 
 
X 
X 
X 
X 
 
X 
X 
X 
X 
X 
X 
 
Recording of 
concomitant 
medications and 
nonstudy 
vaccinations8 
 
X 
X 
X 
X 
 
 
 
 
 
 
  
 
Study completion 
 
 
 
 
 
 
 
 
 
 
 
X 
 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; C = clinic visit; COVID-19 = coronavirus disease 2019; D = day; eDiary = electronic diary; 
EoS = end of study; FDA = US Food and Drug Administration; M = month; MAAE = medically attended adverse event; PBMC = peripheral blood mononuclear cell; 
RT-PCR = reverse transcriptase polymerase chain reaction; SAE = serious adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety 
(telephone) call; SFU = Safety Follow-Up; UNS = unscheduled visit; V = visit. 
Note: In accordance with “FDA Guidance on Conduct of Clinical Trials of Medical Products during COVID-19 Public Health Emergency” (DHHS 2020), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. 
1. 
The Screening Visit and Day 1 (vaccination) visit can be combined and occur on the same day. 

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2. 
Safety follow-up via eDiary questionnaire will be performed every 2 weeks from Day 36 to Day 162, and from Day 202 to Day 342. These study days are relative to Day 1 
vaccination. Adverse reactions recorded in the eDiary beyond Day 7 should be reviewed by the study site staff either during the next scheduled telephone call or at the next 
study site visit. 
3. 
Physical examination: A full physical examination, including height and weight, will be performed on Day 1. Symptom-directed physical examinations may be performed at 
other time points at the discretion of the investigator. Any clinically significant finding identified during a study visit should be reported as an MAAE. Vital signs are to be 
collected pre- and post-vaccination on the day of injection (Day 1) only. When applicable, vital sign measurements should be performed before blood collection. For 
participants who are febrile (body temperature ≥ 38.0°C [100.4°F]) before injection on Day 1, the visit must be rescheduled within the relevant window period to receive the 
injection. Afebrile participants with minor illnesses may be vaccinated at the discretion of the investigator. 
4. 
Sample must be collected prior to vaccination on Day 1.  
5. 
The nasopharyngeal swab sample, collected prior to vaccination on Day 1, will be used to ascertain the presence of SARS-CoV-2 via RT-PCR. The nasopharyngeal swab 
sample will also be collected within 24 hours if participant experience signs and symptoms of SARS-CoV-2 infection. 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-1283, mRNA-1283.211, or 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 judgment to decide if an NP swab should be 
collected. The collection of an NP swab prior to the Day 1 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. 
6. 
Trained site 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 nonstudy vaccinations temporally associated with these events. In addition, study personnel will collect information on 
known participant exposure to someone with known COVID-19 or SARS-CoV-2 infection and on participant experience of COVID-19 symptoms. Sites will collect this 
information for eDiary days only if eDiary responses indicate the need for follow-up via telephone. 
7. 
All concomitant medications relevant to or for the treatment of an SAE or MAAE will be recorded from Day 1 through the EoS Visit (Day 366). 
8. 
All concomitant medications and nonstudy vaccinations will be recorded through 28 days following injection. 

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10.2. 
APPENDIX 2: Study Governance Considerations 
10.2.1. 
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, IB, and other relevant documents (eg, 
advertisements) must be submitted to an IRB by the investigator and reviewed and 
approved by the IRB before the study is initiated. 
• Any amendments to the protocol will require IRB 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 annually or 
more frequently in accordance with the requirements, policies, and procedures 
established by the IRB. 
− Notifying the IRB of SAEs or other significant safety findings as required by IRB 
procedures. 
− Providing oversight of the conduct of the study at the site and adherence to 
requirements of 21 CFR, ICH guidelines, the IRB, European regulation 536/2014 
for clinical studies (if applicable), and all other applicable local regulations. 
10.2.2. 
Study Monitoring  
Before an investigational site can enter a participant into the study, a representative of the 
Sponsor 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 the Sponsor or its representatives. 
This will be documented in a Clinical Study Agreement between the Sponsor, the 
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 the Sponsor 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 
review, and inspection by providing direct access to the source data and/or 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 the Sponsor 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. 
The monitor will be available between visits if the investigator(s) or other staff needs 
information or advice. 
10.2.3. 
Audits and Inspections  
The Sponsor, their designee(s), the IRB, 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 the Sponsor, their designee(s), the IRB, or regulatory 

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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 the Sponsor, a regulatory authority, and the IRB 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 (R2), and any applicable 
regulatory requirements. The investigator should contact the Sponsor 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. 
10.2.4. 
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. 
10.2.5. 
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. 
10.2.6. 
Informed Consent/Assent Process 
The informed consent document(s) must meet the requirements of 21 CFR 50, local regulations, 
ICH guidelines, Health Insurance Portability and Accountability Act (HIPAA) requirements, 
where applicable, and the IRB or study center. All consent documents will be approved by the 
appropriate IRB. The actual ICF used at each center may differ, depending on local regulations 
and 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 IRB prior to the form being used. 

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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 them 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, 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 is not required to sign another ICF if the rescreening occurs 
within 28 days from the previous ICF signature date (within the initial screening period). 
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 CoVs. 
10.2.7. 
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) 
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) 
will be promptly notified. 

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Any modifications to the protocol or the ICF, which may impact the conduct of the study or the 
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 to by the investigator(s), and approved by the relevant IRB(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) must be provided to 
the Sponsor before the study is initiated. 
Administrative changes to 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 to by the investigators, and notified to the IRB(s). 
10.2.8. 
Protocol Deviations  
Noncompliance may be 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 and reported to the study monitor. Protocol deviations must be sent to the reviewing 
IRB per their policies. The site investigator is responsible for knowing and adhering to the 
reviewing IRB requirements. 
10.2.9. 
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. 
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 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. 

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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, the 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. 
10.2.10. 
Sample Retention and Future Biomedical Research 
The Sponsor may store samples for the time frame specified in the ICF to achieve study 
objectives. 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 measures of adaptive 
immunity to SARS-CoV-2 to include humoral and cellular immune assay methodologies on any 
remaining blood or serum samples, including samples from participants who are screened but are 
not subsequently enrolled. These analyses will extend the search for other potentially relevant 
biomarkers to investigate the effect of the mRNA-1283 vaccines as well as to determine how 
changes in biomarkers 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. 
10.2.11. 
Safety Oversight 
Safety monitoring for this study will include an unblinded DSMB. 
Blinded safety monitoring for this study will include study team members, inclusive of, at a 
minimum, the Sponsor medical monitor, Sponsor safety physician (from Pharmacovigilance), 
and CRO medical monitor. The study team will conduct ongoing safety reviews during the study 
and will be responsible for monitoring of safety concerns during the study, as described in the 
Safety Management Plan. 
An independent DSMB, composed of external and independent subject matter experts and an 
unblinded statistician, will conduct unblinded reviews of safety data on an ad hoc basis as 
requested by the study team members. 

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Details regarding the DSMB composition, responsibilities, procedures, and frequency of data 
review will be defined in their respective charters. 
An independent 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. 
10.2.12. 
Dissemination of Clinical Study Data 
The Sponsor shares information about clinical trials and results on publicly accessible websites, 
based on international and local legal and regulatory requirements, and other clinical trial 
disclosure commitments established by pharmaceutical industry associations. These websites 
include clinicaltrials.gov, EU clinical trial register (eu.ctr), as well as some national registries. 
10.2.13. 
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 in the 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 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 
onsite monitoring) are provided in the clinical monitoring 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). 

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• 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 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. 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. 
Quality assurance 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 quality assurance 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 onsite inspections/audits and source data checks. Direct access to source documents is 
required for the purpose of these periodic inspections/audits. 
10.2.14. 
Data Collection and Management 
This study will be conducted in compliance with ICH GCP 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 study 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. 
Adverse events will be coded with MedDRA. Concomitant medications will be coded using 
WHO – Drug Reference List. 

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10.2.15. 
Source Documents 
Source documents are original documents or certified copies and include, but are not limited to, 
eDiaries, medical and hospital records, screening logs, ICFs, 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 case report form 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. Current medical records must also be available. 
The Sponsor 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. 
10.2.16. 
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 the Sponsor 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. 
10.2.17. 
Study and Site Closure 
If the study is prematurely terminated or suspended, the Sponsor shall promptly inform the 
investigators, the 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, discontinue enrollment, 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. 

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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 or 
local health authorities, the Sponsor's procedures, or GCP guidelines 
• Inadequate recruitment of participants by the investigator 
• Discontinuation of further mRNA-1283 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. 
10.2.18. 
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 the 
Sponsor. 

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10.3. 
APPENDIX 3: Contraceptive Guidance 
Definitions: Woman of Childbearing Potential 
Women 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 
vaccination at Day 1, additional evaluation should be considered. 
Women in the following categories are not considered women of childbearing potential: 
1. Premenarchal 
2. Premenopausal, surgically sterile female with 1 of the following: 
a. Documented complete hysterectomy 
b. Documented surgical sterilization 
For individuals with permanent infertility due to an alternate medical cause other than the 
above (eg, Müllerian agenesis, androgen insensitivity), investigator discretion should be 
applied to 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:  
− 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. 
− 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, 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 nonestrogen 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. 
Contraception Guidance: 
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 that periodic abstinence (eg, calendar, ovulation, symptothermal, postovulation methods) 
and withdrawal are not acceptable methods of contraception. 

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10.4. 
APPENDIX 4: Adverse Events of Special Interest Terms for mRNA-1273 
Investigators should report all events that fall into the following categories as AESIs for mRNA-
1273 per the reporting processes specified in Section 7.4.5. The following AESIs are medical 
concepts that may be related to COVID-19 or are of interest in COVID-19 vaccine safety 
surveillance. Even if the events below occur in the setting of COVID infection, the event should 
still be reported as an AESI if it is one of the medical concepts below. 
Medical Concept 
Additional Notes 
Anosmia, Ageusia 
• 
New onset COVID-associated or idiopathic events without other 
etiology excluding congenital etiologies or trauma. 
Subacute thyroiditis 
• 
Including but not limited to events of atrophic thyroiditis, 
autoimmune thyroiditis, immune-mediated thyroiditis, silent 
thyroiditis, thyrotoxicosis, and thyroiditis. 
Acute pancreatitis 
• 
Including but not limited to events of autoimmune pancreatitis, 
immune-mediated pancreatitis, ischemic pancreatitis, edematous 
pancreatitis, pancreatitis, acute pancreatitis, hemorrhagic 
pancreatitis, necrotizing pancreatitis, viral pancreatitis, and 
subacute pancreatitis. 
• 
Excluding known etiologic causes of pancreatitis (alcohol, 
gallstones, trauma, recent invasive procedures). 
Appendicitis 
• 
Include any event of appendicitis. 
Rhabdomyolysis 
• 
New onset rhabdomyolysis without known etiology such as 
excessive exercise or trauma. 
Acute respiratory distress 
syndrome (ARDS) 
• 
Including but not limited to new events of ARDS and 
respiratory failure. 
Coagulation disorders 
• 
Including but not limited to thromboembolic and bleeding 
disorders, disseminated intravascular coagulation, pulmonary 
embolism, deep vein thrombosis. 
Acute cardiovascular injury 
• 
Including but not limited to myocarditis, pericarditis, 
microangiopathy, coronary artery disease, arrhythmia, stress 
cardiomyopathy, heart failure, or acute myocardial infarction. 
Acute kidney injury 
• 
Include events with idiopathic or autoimmune etiologies. 
• 
Exclude events with clear alternate etiology (trauma, infection, 
tumor, or iatrogenic causes such as medications or radiocontrast 
agents, etc). 
• 
Include all cases that meet the following criteria: 
o Increase in serum creatinine by ≥ 0.3 mg/dL 
(≥ 26.5 µmol/L) within 48 hours; OR 
o Increase in serum creatinine to ≥ 1.5 times baseline, 
known or presumed to have occurred within prior 
7 days; OR 
o Urine volume ≤ 0.5 mL/kg/hour for 6 hours. 

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Medical Concept 
Additional Notes 
Acute liver injury 
• 
Include events with idiopathic or autoimmune etiologies. 
• 
Exclude events with clear alternate etiology (trauma, infection, 
tumor, etc). 
• 
Include all cases that meet the following criteria: 
o > 3-fold elevation above the upper normal limit for ALT or 
AST OR 
o > 2-fold elevation above the upper normal limit for total 
serum bilirubin or gamma glutamyl transferase or alkaline 
phosphatase. 
Dermatologic findings 
• 
Chilblain-like lesions 
• 
Single organ cutaneous vasculitis 
• 
Erythema multiforme 
• 
Bullous rashes 
• 
Severe cutaneous ARs including but not limited to: 
Stevens-Johnson syndrome, Toxic Epidermal Necrolysis, Drug 
Reaction with Eosinophilia and Systemic Symptoms, and fixed 
drug eruptions. 
Multisystem inflammatory 
disorders 
• 
Multisystem inflammatory syndrome in adults. 
• 
Multisystem inflammatory syndrome in children. 
• 
Kawasaki’s disease. 
Thrombocytopenia 
• 
Platelet counts < 150 × 109 per mm3. 
• 
Including but not limited to: immune thrombocytopenia, platelet 
production decreased, thrombocytopenia, thrombocytopenic 
purpura, thrombotic thrombocytopenic purpura, or hemolysis, 
elevated liver enzymes, low platelet count (HELLP) syndrome. 
Acute aseptic arthritis 
• 
New onset aseptic arthritis without clear alternate etiology 
(eg, gout, osteoarthritis, and trauma). 
New onset of or worsening of 
neurologic disease 
• 
Including but not limited to:  
o Guillain-Barre syndrome 
o Acute disseminated encephalomyelitis (ADEM) 
o Peripheral facial nerve palsy (Bell’s palsy) 
o  Transverse myelitis 
o Encephalitis/Encephalomyelitis 
o Aseptic meningitis 
o Febrile seizures 
o Generalized seizures/convulsions 
o Stroke (Hemorrhagic and non-hemorrhagic)  
o Narcolepsy 

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Medical Concept 
Additional Notes 
Anaphylaxis 
• 
Anaphylaxis as defined per Section 7.4.4. 
• 
Follow reporting procedures per Section 7.4.11. 
Other syndromes 
• 
Fibromyalgia 
• 
Postural Orthostatic Tachycardia Syndrome 
• 
Chronic Fatigue Syndrome (includes myalgic encephalomyelitis 
and postviral fatigue syndrome) 
• 
Myasthenia gravis 
 
 
 

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10.5. 
APPENDIX 5: Protocol Amendment History 
Amendment 1, 22 Oct 2021: 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 change the dose levels of mRNA-1283 to 
 and of mRNA-
1283.211 to 
, and to remove the mRNA-1283.351 arm. In order to 
accomplish this, an additional arm of mRNA-1283 was added. The dose modification and 
removal of mRNA-1283.351 arm was in response to a review of topline results from the 
interim analysis of the Phase 1 Study mRNA-1283-P101.  
2. The study was changed to Phase 2a to reflect that the study is continuing dose-ranging for 
mRNA-1283 to identify the appropriate dose levels for continued clinical development.  
3. The size of each of the arms of the study were increased from 35 to 70 participants to 
improve the precision in the descriptive summary statistics.  
4. Minor changes have been made throughout the protocol to provide additional clarity and 
correct grammatical or spelling errors. 
Summary of Major Changes from Original Protocol to Protocol Amendment 1: 
Section # and Name 
Description of Change 
Brief Rationale 
Title Page, Signature Page, 
Protocol Amendment Summary 
of Changes, and Header  
• Updated the protocol 
version and date.  
• Added Protocol 
Amendment Summary of 
Changes for 
Amendment 1.  
Updated to reflect the new 
version and date.  
Throughout the protocol 
• Minor updates to language 
Updates for improved 
clarity and to correct 
grammatical or spelling 
mistakes. 
Title Page, Signature Page, 
Declaration of Investigator, 
Protocol Synopsis 
• Changed the protocol title 
to remove the mention of 
specific variants of 
mRNA-1283 
To avoid future changes in 
the protocol title if 
additional variants are 
added to the study. 
Title Page, Signature Page, 
Declaration of Investigator, 
Protocol Synopsis, Section 1.1 
(Study Rationale), Section 3.1 
(General Design) 
• Changed study phase to 
Phase 2a 
Updated to reflect the new 
dose-ranging nature of the 
study. 
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Section # and Name 
Description of Change 
Brief Rationale 
Protocol Synopsis, Section 3.1 
(General Design), Section 5.3.1 
(Study Vaccine Preparation) 
• Changed the dose levels of 
the mRNA-1283 arms of 
the study to 
 
 (added an arm 
to the mRNA-1283 portion 
of the study). 
• Changed the dose levels of 
the mRNA-1283.211 arms 
to 
. 
Analysis of topline results 
from the interim analysis of 
Study mRNA-1283-P101 
support a lower dose 
profile for mRNA-1283. 
The mRNA-1283-P101 
results are currently 
blinded and interim 
analysis results of the study 
will be summarized after 
study unblinding.   
Title Page, Signature Page, 
Declaration of Investigator, 
Protocol Synopsis, Section 1.1 
(Study Rationale), Section 
1.2.3 (mRNA-1283.351), 
Section 1.2.4 (now Section 
1.2.3 Nonclinical Studies), 
Section 3.1 (General Design), 
Section 3.3 (Justification for 
Dose, Control Product, and 
Choice of Study Population), 
Section 4 (Study Population), 
Section 5.1 (Investigational 
Products Administered), 
Section 5.3.1 (Study Vaccine 
Preparation), Section 5.3.4 
(Study Vaccine Packaging and 
Labeling), Section 5.3.5 (Study 
Vaccine Storage), Section 8.3 
(Sample Size Determination), 
Section 8.5.4.1 (Analysis for 
the Primary Immunogenicity 
Objective), Section 10.1 
(Appendix 1: Schedule of 
Events) 
1. Removed the mRNA-
1283.351 arm of the study 
The multivalent vaccine 
mRNA-1283.211 contains 
the B.1.351 variant mRNA 
and so mRNA-1283.351 
will not be evaluated 
separately.  
Protocol Synopsis, Section 3.1 
(General Design), Section 4 
(Study Population), Section 8.3 
(Sample Size Determination) 
2. Changed the number of 
participants per arm from 
35 to 70  
To improve the descriptive 
summary value of each of 
the arms of the study. 
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Section # and Name 
Description of Change 
Brief Rationale 
Protocol Synopsis 
3. Changed projected date of 
first participant enrolled 
4. Changed projected date of 
first participant completed 
To reflect updated 
projected study timelines. 
Protocol Synopsis 
5. Increased number of 
planned sites to 13 
To reflect the planned 
increase in the number of 
sites in the study. 
Protocol Synopsis, Section 2 
(Objectives and Endpoints) 
6. Updated language for the 
Objectives and Endpoints  
To improve clarity in the 
language surrounding the 
mRNA-1283 booster 
vaccines.  
Protocol Synopsis, Section 4.2 
(Exclusion Criteria) 
7. Updated Exclusion 
Criteria 
To improve clarity and 
align protocol language 
with other booster study 
protocols. 
Protocol Synopsis, Section 
8.6.1 (Primary Analysis) 
8. Added statement that the 
protocol may be amended 
based on the results of the 
primary analysis.  
Clarifying statement. 
Section 1.2.5 (now 1.2.4 
Clinical Studies) 
9. Removed language stating 
that no clinical studies 
with mRNA-1283 have 
been completed 
Study mRNA-1283-P101 
has completed enrollment 
and topline results have 
been prepared. 
Section 1.3.2 (Risks from Study 
Participation and Their 
Mitigation 
10. Removed discussion of 
the potential for vaccine 
associated enhanced 
disease 
Based on the mRNA-1273-
P301 results, there are no 
data suggestive of vaccine 
associated enhanced 
disease.