A Phase 1/2, Randomized, Stratified, Observer-Blind, Dose-Ranging Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of mRNA-1010 Seasonal Influenza Vaccine in Healthy Adults 18 Years and Older
Phase: PHASE1
Conditions: Seasonal Influenza
Sponsor: ModernaTX, Inc.

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
Confidential 
Page 1 
CLINICAL STUDY PROTOCOL 
Protocol Title: 
A Phase 1/2, Randomized, Stratified, Observer-Blind, 
Dose-Ranging Study to Evaluate the Safety, Reactogenicity, 
and Immunogenicity of mRNA-1010 Seasonal Influenza 
Vaccine in Healthy Adults 18 Years and Older 
Protocol Number: 
mRNA-1010-P101 
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(s): 
IND 27460 
Amendment Number: 
4 
Date of Amendment 4: 
03 Feb 2022 
Date of Amendment 3: 
21 Oct 2021 
Date of Amendment 2: 
19 Aug 2021 
Date of Amendment 1: 
22 Jul 2021 
Date of Original Protocol: 
19 Apr 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. 
NCT #: NCT04956575
PPD
PPD
PPD

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
Confidential 
Page 2 
PROTOCOL APPROVAL – SPONSOR SIGNATORY 
Study Title: 
A Phase 1/2, Randomized, Stratified, Observer-Blind, Dose-Ranging 
Study to Evaluate the Safety, Reactogenicity, and Immunogenicity of 
mRNA-1010 Seasonal Influenza Vaccine in Healthy Adults 18 Years 
and Older 
Protocol Number: 
mRNA-1010-P101 
Amendment Number: 
4 
Approval Date: 
03 Feb 2022 
 
Protocol accepted and approved by: 
 
 
 
 
 
See e-Signature and date at the end 
of the document 
 
 
 
 
 
ModernaTX, Inc. 
200 Technology Square 
Cambridge, MA 02139 
Telephone: 
 
 
Date 
 
 
 
PPD
PPD

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
Confidential 
Page 3 
DECLARATION OF INVESTIGATOR 
I have read and understood all sections of the protocol titled A Phase 1/2, Randomized, Stratified, 
Observer-Blind, Dose-Ranging Study to Evaluate the Safety, Reactogenicity, and Immunogenicity 
of mRNA-1010 Seasonal Influenza Vaccine in Healthy Adults 18 Years and Older and the most 
recent version of the investigator’s brochure. 
I agree to supervise all aspects of the protocol and to conduct the clinical investigation in 
accordance with the current protocol, the International Council for Harmonisation (ICH) 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 subinvestigator. 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 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, United States federal regulations, and ICH E6(R2) GCP 
guidelines. 
 
Signature of Principal Investigator 
 
 
Date 
 
 
 
 
Printed Name of Principal Investigator 
 
 
 

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
Confidential 
Page 4 
Protocol Amendment Summary of Changes 
DOCUMENT HISTORY 
Document 
Date 
Amendment 4 
03 Feb 2022 
Amendment 3 
21 Oct 2021 
Amendment 2 
19 Aug 2021 
Amendment 1 
22 Jul 2021 
Original Protocol 
19 Apr 2021 
 
Amendment 4, 03 Feb 2022 (Current Amendment) 
Main Rationale for the Amendment: 
The purpose of this amendment is to add the Phase 2 Extension part to test 3 dose levels of 
mRNA-1010 (6.25, 12.5, and 25 µg total mRNA; Vaccination Groups 1 to 3). 
The summary of changes table provided here describes the major changes made in Amendment 4 
relative to Amendment 3, including the sections modified and the corresponding rationales. As 
applicable, the synopsis of Amendment 4 has been modified to correspond to changes in the body 
of the protocol. Minor editorial and/or formatting changes are not provided in this summary table. 
Summary of Major Changes From Protocol Amendment 3 to Protocol Amendment 4: 
Section # and Name 
Description of Change 
Brief Rationale 
Synopsis: Overall Study 
Design; Section 4.1 
(General Design); 
Section 4.2 (Scientific 
Rationale for Study 
Design); Section 6.1 
(Investigational Products 
Administered) 
• 
Added Phase 2 Extension part to the 
study to test dose levels of 6.25, 
12.5, and 25 µg total mRNA or a 
single dose of a licensed 
quadrivalent seasonal influenza 
vaccine (active comparator). 
• 
Based on interim analysis of the 
Phase 1/2 study, vaccination with 
mRNA-1010 elicited HAI 
antibodies at all dose levels tested. 
In the Phase 2 Extension part of the 
study, the Sponsor intends to test 
lower dose levels of 6.25 and 
12.5 µg. Thus, the Phase 2 
Extension part will evaluate the 
immunogenicity of mRNA-1010 at 
proposed total dose levels of 6.25, 
12.5, and 25 µg in addition to an 
active comparator. 
Synopsis: Number of 
Participants; Section 4.1 
(General Design); 
Section 6.2 
(Randomization); 
Section 9.3 (Sample Size 
Determination) 
• 
Updated to describe enrollment and 
randomization of approximately 
200 participants into the Phase 2 
Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 

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03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
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Section # and Name 
Description of Change 
Brief Rationale 
Synopsis: Study Eligibility 
Criteria; Section 5.2 
(Phase 2 Northern 
Hemisphere and Phase 2 
Extension) 
• 
Updated to include inclusion and 
exclusion criteria for the Phase 2 
Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Synopsis: Study 
Treatments; Section 6 
(Study Treatment) 
• 
Updated to specify that the vaccine 
to be tested for the Phase 2 
Extension part will be the same as 
the vaccine tested in the Phase 2 NH 
part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Synopsis: Procedures and 
Assessments; Section 8.1 
(Safety Assessments and 
Procedures) 
• 
Updated to reflect procedures and 
assessments in the Phase 2 
Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Synopsis: Statistical 
Methods (Sample Size); 
Section 9.3 (Sample Size 
Determination) 
• 
Updated to describe the sample size 
for each group within the Phase 2 
Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Synopsis: Immunogenicity 
Analyses; Section 9.5.3 
(Immunogenicity 
Analyses) 
• 
Updated to define the rate of 
seroconversion for the Phase 2 NH 
part and to describe immunogenicity 
analyses in the Phase 2 Extension 
part. 
• 
Updated for clarity and (Part 2 NH) 
and per the addition of the Phase 2 
Extension part. 
Section 1.2 (Schema), 
Figure 3 
• 
Added this figure to present the 
study schema for the Phase 2 
Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 1.3 (Schedule of 
Events), Table 3 
• 
Added this table as the Phase 2 
Extension part Schedule of Events. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 2.3.1 (Known 
Potential Benefits) 
• 
Updated to describe potential benefit 
for participants enrolled in the 
Phase 2 Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 2.3.3 (Overall 
Benefit/Risk Conclusion); 
Section 4.3 (Choice of 
Vaccine Dose) 
• 
Updated to include rationale for 
doses in the Phase 2 Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 3.2 (Phase 2 
Northern Hemisphere and 
Phase 2 Extension) 
• 
Updated to indicate objectives and 
endpoints for the Phase 2 Extension 
part are the same as those for the 
Phase 2 NH part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 6.3 
(Preparation/Handling/ 
Storage/Accountability) 
• 
Updated to describe investigational 
product that will be provided in the 
Phase 2 Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 6.5.2 
(Concomitant Medications 
and Therapies) 
• 
Clarified and updated the timing of 
seasonal influenza vaccine that is 
considered concomitant therapy. 
• 
Updated for clarity. 
Section 6.6 (Intervention 
After End of the Study) 
• 
Updated to indicate that no 
investigational product will be 
• 
Updated for clarity. 

ModernaTX, Inc. 
03 Feb 2022 
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Section # and Name 
Description of Change 
Brief Rationale 
provided to participants after the end 
of study. 
Section 7.1.2 (Pause Rules 
for the Phase 2 Northern 
Hemisphere and the 
Phase 2 Extension Parts of 
the Study 
• 
Updated to indicate that pausing 
rules apply to both Phase 2 parts of 
the study. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Section 8.1.1 (Use of 
Electronic Diaries) 
• 
Removed language indicating that 
participants have a limited window 
on the following day to complete 
assessments for the previous day. 
• 
Removed language specifically 
describing the treatment of new 
safety information reported during 
safety telephone calls or at site visits 
that was not already captured in the 
eDiary. 
• 
Updated for practicality and clarity. 
Section 8.1.6 
(Assessments for 
Respiratory Viral 
Infections) 
• 
Added description of NP swab 
sampling of participants in the 
Phase 2 Extension parts with signs 
or symptoms of CDC-defined ILI or 
of COVID-19).  
• 
Updated for clarity. 
Section 8.4.3 (Solicited 
Adverse Reactions) 
• 
Added clarification of recording 
solicited adverse reactions. 
• 
Updated for clarity. 
Section 8.9 (Biomarkers) 
• 
Updated to indicate that biomarker 
assessments will be evaluated in the 
Phase 2 Extension part. 
• 
Added per the addition of the 
Phase 2 Extension part. 
Abbreviations: COVID-19 = coronavirus disease 2019; HAI = hemagglutination inhibition; mRNA = messenger RNA; 
NH = Northern Hemisphere; NP = nasopharyngeal swab.  

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03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
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1. 
PROTOCOL SUMMARY 
1.1. 
Synopsis 
Name of Sponsor/Company: ModernaTX, Inc. 
Name of Investigational Product: mRNA-1010 
Name of Active Ingredient: mRNA-1010 
Protocol Title: A Phase 1/2, Randomized, Stratified, Observer-Blind, Dose-Ranging Study to 
Evaluate the Safety, Reactogenicity, and Immunogenicity of mRNA-1010 Seasonal Influenza 
Vaccine in Healthy Adults 18 Years and Older 
Protocol Number: mRNA-1010-P101; Amendment 4 
Study Period: Approximately 18 months 
Phase of Development: Phase 1/2 
Objectives and Endpoints: 
The objectives and endpoints for the Phase 1/2 part of the study are presented in the table below. 
Objectives 
Endpoints 
Primary 
 
• 
To evaluate the safety and reactogenicity 
of 3 dose levels (50, 100, and 200 µg) of 
mRNA-1010 vaccine administered as a 
single dose 
• 
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, AESIs, and MAAEs 
from Day 1 through Day 181/EoS 
• 
Safety laboratory abnormalities through 7 days 
after vaccination 
• 
To evaluate the humoral immunogenicity 
of 3 dose levels (50, 100, and 200 µg) of 
mRNA-1010 vaccine administered as a 
single dose against vaccine-matched 
influenza A and B strains at Day 29 
• 
GMT and GMFR at Day 29 compared with Day 
1 (baseline) and percentage of participants with 
seroconversion, defined as a Day 29 titer ≥ 1:40 if 
baseline is < 1:10 or a 4-fold or greater rise if 
baseline is ≥ 1:10 in anti-HA antibodies measured 
by HAI assay 
 
 

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
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Secondary 
 
• 
To 
evaluate 
the 
humoral 
immunogenicity of 3 dose levels (50, 
100, and 200 µg) of mRNA-1010 
vaccine administered as a single dose 
against vaccine-matched influenza A 
and B strains at all evaluable humoral 
immunogenicity time points 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI or MN assays at all evaluable 
humoral immunogenicity time points compared 
with Day 1 (baseline) 
Exploratory (May be Performed) 
 
• 
To 
evaluate 
the 
humoral 
immunogenicity of 3 dose levels (50, 
100, and 200 µg) of mRNA-1010 
vaccine administered as a single dose 
against vaccine-mismatched or drifted 
influenza A and B strains 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI or MN assays against vaccine-
mismatched or drifted strains compared with Day 
1 (baseline) 
• 
To evaluate the cellular immunogenicity 
of 3 dose levels (50, 100, and 200 µg) of 
mRNA-1010 vaccine administered as a 
single dose in a subset of participants 
• 
Frequency, magnitude, and phenotype of virus-
specific T-cell and B-cell responses measured by 
flow cytometry or other methods as well as 
targeted repertoire analysis of B cells and T cells 
after vaccination 
• 
To 
further 
characterize 
antibody 
responses, for example, Fc-mediated 
function, avidity, or epitope specificity, 
of 3 dose levels (50, 100, and 200 µg) of 
mRNA-1010 vaccine administered as a 
single dose 
• 
Frequency, specificities, or other endpoints to be 
determined, for further characterization of 
antibody responses 
• 
To assess the occurrence of ILI in study 
participants 
and 
characterize 
their 
immune response to infection and viral 
isolates 
• 
Frequency of RT-PCR-confirmed ILI and 
assessment of immune responses in participants 
with RT-PCR-confirmed ILI 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; EoS = end of study; 
Fc = fragment crystallizable; GMFR = geometric mean fold rise; GMT = geometric mean titer; HA = hemagglutinin; 
HAI = hemagglutination inhibition; ILI = influenza-like illness; MAAE = medically attended adverse event; 
MN = microneutralization; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event. 
 
The objectives and endpoints for the Phase 2 Northern Hemisphere (NH) and the Phase 2 
Extension parts of the study are presented in the table below. 
 
Objectives 
Endpoints 
Primary 
 

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
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• 
To evaluate the humoral immunogenicity 
of mRNA-1010 vaccine relative to that of 
an 
active 
comparator 
against 
vaccine-matched influenza A and B 
strains at Day 29 
• 
GMT at Day 29 as measured by HAI 
• 
Proportion 
of 
participants 
reaching 
seroconversion at Day 29 as measured by HAI 
• 
To evaluate the safety and reactogenicity 
of mRNA-1010 vaccine 
• 
Frequency and grade of each solicited local and 
systemic reactogenicity ARs 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, AESIs, and MAAEs 
from Day 1 through Day 181/EoS 
Secondary 
 
• 
To evaluate the humoral immunogenicity 
of 
each 
vaccine 
group 
against 
vaccine-matched influenza A and B 
strains at Day 29 
• 
The frequency of participants with HAI 
seroconversion and the frequency of participants 
with an HAI titer ≥ 1:40 at Day 29 
• 
GMFR comparing Day 29 to Day 1 (baseline) as 
measured by HAI 
Exploratory (May be Performed) 
 
• 
To evaluate the relative vaccine efficacy 
of mRNA-1010 vaccine to an active 
comparator 
in 
preventing 
RT-PCR-confirmed ILI caused by any 
strain of influenza using different case 
definitions 
• 
RT-PCR-confirmed protocol- or CDC-defined 
ILI that begin at least 14 days after vaccination 
through Day 181/EoS caused by any strain of 
influenza regardless of antigenic match to the 
strains selected for the seasonal vaccine 
• 
To evaluate the humoral immunogenicity 
of mRNA-1010 vaccine to that of an 
active 
comparator 
against 
vaccine-matched or vaccine-mismatched 
influenza A and B strains, including the 
use of alternative methods 
• 
GMT and GMFR of anti-HA antibodies as 
measured by assays such as MN assays or 
alternative methods against vaccine-matched or 
vaccine-mismatched strains on Day 29 compared 
with Day 1 (baseline) 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI against vaccine-mismatched 
strains on Day 29 compared with Day 1 (baseline) 
• 
To evaluate the humoral immunogenicity 
at Days 91 and 181/EoS in a subset of 
participants 
• 
GMT, GMFR, and frequency of participants with 
HAI titers ≥ 1:40 at Days 91 and 181/EoS 
• 
To further characterize the immune 
response to mRNA-1010 vaccine and 
active comparator 
• 
Frequency, specificities, or other endpoints to be 
determined for further characterization of 
immune responses 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; CDC = Centers for 
Disease Control and Prevention; EoS = end of study; GMFR = geometric mean fold rise; GMT = geometric mean titer; 

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
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HA = hemagglutinin; HAI = hemagglutination inhibition; ILI = influenza-like illness; MAAE = medically attended adverse 
event; MN = microneutralization; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event. 
Overall Study Design: This first-in-human study is a Phase 1/2, randomized, observer-blind, 
dose-ranging study to evaluate the safety, reactogenicity, and immunogenicity of mRNA-1010 
vaccine in adult participants ≥ 18 years of age. The study comprises 3 parts: Phase 1/2, Phase 2 
NH, and Phase 2 Extension. 
The Phase 1/2 part of the study will be a randomized, observer-blind, dose-ranging, 
placebo-controlled study to evaluate the safety, reactogenicity, and immunogenicity of 
mRNA-1010 vaccine in healthy adult participants ≥ 18 years of age. The Phase 2 NH and 
Phase 2 Extension parts of the study will be randomized, observer-blind, dose-ranging, 
active-controlled studies to evaluate the immunogenicity, reactogenicity, and safety of 
mRNA-1010 vaccine in medically stable adults 18 years and older. 
All participants in each part of the study will participate in a screening period (up to 28 days 
before Day 1), treatment period (single dose of vaccine on Day 1), and a follow-up period (up 
to 6 months after vaccination). 
In the Phase 1/2 part of the study, the mRNA-1010 vaccine to be tested includes messenger 
RNAs (mRNAs) that encode for the surface glycoprotein hemagglutinins (HAs) of the following 
influenza virus strains recommended by the World Health Organization (WHO) for 2020-2021 
Southern Hemisphere (SH) cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Hong Kong/45/2019(H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
In the Phase 2 NH and Phase 2 Extension parts of the study, the mRNA-1010 vaccine to be 
tested, includes mRNAs that encode for the surface glycoprotein HAs of the following influenza 
virus strains recommended by the WHO for 2021-2022 NH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Cambodia/e0826360/2020 (H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
Different dose levels of mRNA-1010 vaccine will be evaluated. Placebo will be included in the 
Phase 1/2 part and an active comparator (licensed quadrivalent seasonal influenza vaccine) will 

ModernaTX, Inc. 
03 Feb 2022 
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be included in the Phase 2 NH and Phase 2 Extension parts. In the Phase 1/2 part, each 
vaccination group will have 2 stages: initial stage and expansion stage. 
The tables below list the vaccination groups and dose levels that will be evaluated in each part 
of the study, as well as the total number of study participants in each study part and overall. 
Phase 1/2 
 
Number of Participants 
Vaccination 
Group 
Investigational 
Product 
mRNA  
or HA (µg) 
Total  
Dose 
(µg) 
Phase 1/2 
Initial 
Stage 
Expansion 
Stage 
Total 
1 
mRNA-1010 
12.5 
50 
9 
36 
45 
2 
mRNA-1010 
25 
100 
9 
36 
45 
3 
mRNA-1010 
50 
200 
9 
36 
45 
4 
Placebo 
– 
– 
9 
36 
45 
Total 
36 
144 
180 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA. 
Phase 2 NH 
 
Number of Participants 
Vaccination 
Group 
Investigational 
Product 
mRNA  
or HA (µg) 
Total  
Dose (µg) 
Phase 2 NH 
1 
mRNA-1010 
6.25 
25 
150 
2 
mRNA-1010 
12.5 
50 
150 
3 
mRNA-1010 
25 
100 
150 
4 
Active comparator 
15 
60 
50 
Total 
500 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA; NH = Northern Hemisphere. 
Phase 2 Extension 
 
Number of Participants 
Vaccination 
Group 
Investigational 
Product 
Total  
Dose (µg) 
Phase 2 Extension 
1 
mRNA-1010 
6.25 
50 
2 
mRNA-1010 
12.5 
50 
3 
mRNA-1010 
25 
50 
4 
Active comparator 
60 
50 
Total 
200 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA. 
Note: Mass percent in mRNA-1010 is 25% for each of the 4 HAs.  

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Total Number of Participants 
Study Part 
Number of Participants 
Phase 1/2 
180 
Phase 2 NH 
500 
Phase 2 Extension 
200 
Total 
880 
Abbreviations: NH = Northern Hemisphere. 
Healthy (Phase 1/2) and medically stable (Phase 2 NH and Phase 2 Extension) adults ≥ 18 years 
of age will be screened and enrolled. For the Phase 2 NH and Phase 2 Extension parts, 
participants with chronic diseases requiring ongoing medical intervention within the last 
3 months prior to enrollment as well as those with immunocompromising conditions or 
medications will be excluded. 
In the Phase 1/2 part, approximately 180 participants will be randomly assigned in a 1:1:1:1 
ratio to receive mRNA-1010 50 μg, mRNA-1010 100 μg, mRNA-1010 200 μg, or placebo, with 
approximately 45 participants randomly assigned to each vaccination group. A total of 
36 participants (9 participants in each vaccination group) will be randomly assigned in the initial 
stage of the study. The internal safety team (IST) will perform a blinded review of all safety 
data up to 7 days after vaccination from the 36 participants in the initial stage. After the IST 
confirms that no pause rules have been met in the 36 participants in the initial stage, enrollment 
will begin in the expansion stage. A total of 144 participants (36 participants in each vaccination 
group) will be randomly assigned in the expansion stage. Randomization in the expansion stage 
will be stratified by age (18 to < 50 years versus ≥ 50 years) and will be balanced across the 
2 age groups within each vaccination group. 
The Phase 2 NH part of the study will enroll and randomize approximately 500 participants in 
a 3:3:3:1 ratio to 1 of 4 vaccination groups to receive a single dose of mRNA-1010 at different 
dose levels (25, 50, or 100 µg total mRNA) or a single dose of a licensed quadrivalent seasonal 
influenza vaccine (active comparator). Randomization to individual vaccination groups will 
proceed with parallel randomization among the 3 dose levels of mRNA-1010 (25, 50, and 
100 total mRNA; Vaccination Groups 1 to 3) and the active comparator (Vaccination Group 4). 
Randomization will be stratified by age categories (18 to < 50 years, 50 to < 65 years, or 
≥ 65 years) and vaccination status in the previous flu season (received or not received). 
The Phase 2 Extension part of the study will enroll and randomize approximately 
200 participants in a 1:1:1:1 ratio to 1 of 4 vaccination groups to receive a single dose of 
mRNA-1010 at different dose levels (6.25, 12.5, or 25 µg total mRNA) or a single dose of a 
licensed quadrivalent seasonal influenza vaccine (active comparator). Randomization to 

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individual vaccination groups will proceed with parallel randomization among the 3 dose levels 
of mRNA-1010 (6.25, 12.5, or 25 µg total mRNA; Vaccination Groups 1 to 3) and the active 
comparator (Vaccination Group 4). Randomization will be stratified by age categories (18 to 
< 50 years, or ≥ 50 years).  
The Phase 1/2 part of the study comprises 6 scheduled study site visits: screening, Day 1, Day 8, 
Day 29 (Month 1), Day 57 (Month 2), and Day 181 (Month 6). The Phase 2 NH and Phase 2 
Extension parts of the study comprise 5 scheduled study site visits: Screening, Day 1, Day 29 
(Month 1), Day 91 (Month 3), and Day 181 (Month 6). The Phase 2 Extension part also contains 
an optional study site visit on Day 4 for blood sample collection. There are also scheduled safety 
phone calls to collect medically attended adverse events (MAAEs), adverse events (AEs) 
leading to withdrawal from study participation, serious AEs (SAEs), AEs of special interest 
(AESIs), information about concomitant medications associated with these events, and 
information about receipt of nonstudy vaccinations temporally associated with these events. 
These phone calls are scheduled monthly from Day 91 through Day 151 in the Phase 1/2 part 
and on Days 8 and 15 in the Phase 2 NH and Phase 2 Extension parts of the study. 
The study duration will be approximately 7 months for each participant enrolled in each part of 
the study: a screening period of up to 1 month and a study period of 6 months that includes a 
single dose of vaccine on Day 1. The participant’s final visit (ie, end of study [EoS]) will be on 
Day 181 (Month 6), six months after the study vaccination. 
All participants in each part of the study will be followed for safety and reactogenicity. On 
Day 1, participants will be instructed how to document, and report solicited adverse reactions 
(ARs) and influenza-like illness (ILI) symptoms (for Phase 2 NH part only) with a provided 
electronic diary (eDiary). Solicited ARs will be assessed for 7 days (the day of injection and the 
following 6 days) after the study vaccination, and unsolicited AEs will be assessed for 28 days 
after the study vaccination; SAEs, AESIs, and MAAEs will be assessed from Day 1 throughout 
the study. 
All participants in the Phase 1/2 part of the study will provide nasopharyngeal (NP) swab 
samples before the injection on Day 1 for assessment of asymptomatic infection with respiratory 
pathogens, including influenza virus and severe acute respiratory syndrome coronavirus 2 
(SARS-CoV-2). A study site visit or a consultation (unscheduled study visit) will be arranged 
within 24 hours or as soon as possible to collect an NP swab sample if participants experience 
symptoms consistent with the United States (US) Centers for Disease Control and Prevention 
(CDC) definition of ILI and/or coronavirus disease 2019 (COVID-19) during the course of the 
study. 

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For the Phase 2 NH part, as part of the safety assessments, active and passive surveillance for 
ILI will be conducted between Day 1 through Day 181/EoS. For active surveillance, participants 
will be instructed to report whether ILI symptoms have been experienced, 3 to 4 times weekly 
from Day 1 through Day 29 and twice weekly from Day 30 through Day 181/EoS, via eDiary 
or telephone calls. If symptoms occur, participants will be directed to return to the study site as 
soon as possible, but no later than 72 hours after the onset of symptoms, for medical evaluation 
and an NP swab. Participants will be contacted by the study site if they have missed reporting 
in the eDiary. If there is no response to an eDiary prompt for 2 consecutive entries, the study 
site staff will contact the participant by telephone. For passive surveillance, participants will be 
instructed to report symptoms of ILI any time from Day 1 through Day 181/EoS. Participants in 
the Phase 2 NH part who manifest protocol-defined ILI between Day 1 through Day 29 will be 
evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR) testing of an 
NP specimen for influenza (and other respiratory pathogens). An NP swab specimen for 
pathogens, including influenza virus and SARS-CoV-2 will be collected any time from Day 1 
through Day 181/EoS if participants have protocol-defined ILI or symptoms suggestive of 
COVID-19 or other upper or lower respiratory infection at the Investigator’s discretion. 
For the Phase 2 Extension part, a study site visit or a consultation (unscheduled study visit) will 
be arranged within 72 hours after the onset of symptoms to collect an NP swab sample if 
participants experience symptoms consistent with the US CDC definition of ILI and/or 
COVID-19 during the course of the study. 
All participants in the Phase 1/2 part of the study will provide a blood specimen before injection 
on Day 1 and additional blood specimens through the next 6 months for immunogenicity (on 
Days 8, 29, and 181/EoS). In the Phase 2 NH and Phase 2 Extension parts, all participants will 
provide a blood specimen for immunogenicity assessments before injection on Day 1 and then 
on Day 29. In addition, blood samples from a subset of participants at Days 91 and 181/EoS 
may be used for additional assessments. The Phase 2 Extension part also contains an optional 
study site visit on Day 4 for blood sample collection for potential biomarker analysis. 
Furthermore, blood samples for safety or other medical concerns may be collected according to 
the Investigator’s judgment at scheduled study site visits during each part of the study. 
Participants may experience AEs that necessitate an unscheduled visit. There may also be 
situations in which the Investigator asks a participant to report for an unscheduled visit following 
the report of an AE. Additional examinations may be conducted at these visits as necessary to 
ensure the safety and well-being of participants during the study. Electronic case report forms 
should be completed for each unscheduled visit. 

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The study will be observer-blind as to which investigational product (IP; mRNA-1010 or 
placebo in the Phase 1/2 part; mRNA-1010 or the active comparator in the Phase 2 NH and 
Phase 2 Extension parts) or dose level is administered. Participants will receive the IP by 0.5-mL 
intramuscular (IM) injection on Day 1. All participants, study site staff involved in participant 
assessment, and Sponsor personnel (or its designees) will be blinded to individual dosing 
assignment until the study database is locked and unblinded. Preparation of the 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. 
For the Phase 1/2 part, there is 1 planned interim analysis (IA), which will include safety and 
immunogenicity data of all participants (all vaccination groups) after completion of the Day 29 
Visit. For the Phase 2 NH and Phase 2 Extension parts, an IA of safety (reactogenicity and 
immunogenicity as applicable) will be performed after participants have completed the Day 29 
Visit for each part of the study. 
Immunizations for the Phase 1/2 part of the study are planned during the NH summer and all 
participants will be recommended to receive a licensed 2021-22 NH seasonal influenza vaccine 
during their participation in the study after completion of the Day 29 Visit. Immunizations for 
the Phase 2 NH part of the study are planned during the NH influenza season. Immunizations 
for the Phase 2 Extension part are planned during the NH spring. 
Safety Oversight: Safety monitoring for this study will include blinded study team members, 
inclusive of, at a minimum, the Sponsor’s medical monitor, medical monitor of the contract 
research organization (CRO), a blinded IST, and an unblinded Data and Safety Monitoring 
Board (DSMB). The study team will conduct ongoing blinded safety reviews during the study 
and will be responsible for notifying the IST and DSMB of potential safety signal events or the 
triggering of pause rules. 
The IST will consist of at least 2 Sponsor physicians who will be voting members not directly 
involved in the clinical development of the study. For the initial stage in the Phase 1/2 part of 
the study, the IST will conduct a blinded review of all available safety data after at least 
36 participants (9 participants per vaccination group) have completed their Day 8 Visit. 
Vaccination of the remaining participants in the expansion stage will continue in each 
vaccination group if no pause rules have been met and the safety and tolerability are acceptable. 
Prior to the start of the Phase 2 NH part of the study, the IST will also conduct a blinded review 
of available safety data from the Phase 1/2 part. Finally, the IST will also conduct ad hoc reviews 
as requested by the study medical monitor and the study team. 
An independent unblinded DSMB will be used throughout the conduct of this study. This 
committee will be composed of independent members with relevant therapeutic and/or 

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biostatistical expertise to allow for the ongoing unblinded review of safety data from this study 
population. Safety data will be reviewed according to intervals defined in the DSMB charter and 
will also occur as needed when study stopping or pausing criteria are met, or as otherwise 
requested by the study team and/or IST. 
Details regarding the IST and DSMB composition, responsibilities, procedures, and frequency 
of data review will be defined in their respective charters. 
Study Duration: Approximately 7 months for each participant in each part of the study. 
Number of Participants: Approximately 180 participants will be enrolled and randomized in 
the Phase 1/2 part of the study. The Phase 2 NH part will enroll and randomize approximately 
500 participants. The Phase 2 Extension part will enroll and randomize approximately 
200 participants. There will be a total of 880 participants in the entire study. 
Study Eligibility Criteria 
Phase 1/2 Inclusion Criteria: 
Each participant must meet all of the following criteria at the Screening Visit and at Day 1, 
unless noted otherwise, to be enrolled in the study: 
1. Is an adult, ≥ 18 years of age at the time of consent (Screening Visit), who is in good 
health, in the opinion of the Investigator, based on review of medical history and 
physical examination performed at screening. 
2. Understands and is willing and physically able to comply with protocol-mandated 
follow-up, including all procedures, in the opinion of the Investigator. 
3. Has provided written informed consent for participation in this study, including all 
evaluations and procedures as specified in this protocol. 
4. Has a body mass index of 18 kg/m2 to 35 kg/m2 (inclusive) at the Screening Visit. 
5. If female and is not of childbearing potential, may be enrolled in the study. A 
follicle-stimulating hormone (FSH) level may be measured at the discretion of the 
Investigator to confirm postmenopausal status. 
6. If female and of childbearing potential, meets all of the following criteria to be enrolled 
in the study: 
• Has a negative pregnancy test at the Screening Visit and on the day of vaccination 
(Day 1). 

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• Has practiced adequate contraception or has abstained from all activities that could 
result in pregnancy for at least 28 days prior to Day 1. Adequate female 
contraception is defined as consistent and correct use of a Food and Drug 
Administration (FDA)-approved contraceptive method in accordance with the 
product label. 
• Has agreed to continue adequate contraception through 3 months following vaccine 
administration. 
• Is not currently breastfeeding. 
Phase 1/2 Exclusion Criteria: 
Participants meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had significant exposure to someone with laboratory-confirmed SARS-CoV-2 
infection, COVID-19, or ILI in the past 14 days prior to the Screening Visit, as defined 
by the CDC as a close contact with someone who has COVID-19. 
2. Has a positive SARS-CoV-2 RT-PCR or antigen test in the past 10 days prior to the 
Screening Visit. 
a. A participant who has a positive SARS-CoV-2 serological test in the past 10 days 
prior to the Screening Visit but is otherwise asymptomatic and does not have a 
positive SARS-CoV-2 RT-PCR or antigen test at the Screening Visit may still be 
enrolled if they meet the study eligibility criteria. 
b. A participant who has a positive SARS-CoV-2 RT-PCR or antigen test in the past 
10 days prior to the Screening Visit may be enrolled 10 days after symptom onset 
or 10 days after the date of the first positive SARS-CoV-2 RT-PCR test without 
repeat testing, provided the participant is asymptomatic and meets the study 
eligibility criteria as well as the CDC recommendation for duration of isolation and 
precautions. 
c. Additionally, a participant who meets all study eligibility criteria (note exclusion 
criterion No. 4) at Screening Visit but later tests positive for SARS-CoV-2 at 
Visit 1 will continue participation in the study. 
3. Has clinical screening laboratory values (white blood cell count, hemoglobin, platelets, 
alanine aminotransferase, aspartate aminotransferase, creatinine, alkaline phosphatase, 
and total bilirubin) > Grade 1. 
4. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 

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the 28-day screening window and will retain their initially assigned participant 
number. 
5. Has a pre-existing medical condition that is not stable, at the discretion of the 
Investigator. A stable medical condition is defined as disease not requiring significant 
change in therapy or hospitalization for worsening disease during the 2 months before 
enrollment. Participants may be rescreened if they are not medically stable at the 
Screening Visit. Medical conditions include (but are not limited to) the following: 
a. Uncontrolled hypertension or systolic blood pressure (BP) > 150 mm Hg or 
diastolic BP > 90 mm Hg at the Screening Visit. 
b. Congestive heart failure. 
c. Unstable angina or exacerbation of coronary artery disease within 6 months before 
the day of vaccination (Day 1) requiring cardiac intervention or new cardiac 
medications to control symptoms. 
d. Diabetes requiring the use of medicine (injectable or oral) or not controlled with 
diet. 
e. Chronic obstructive pulmonary disease, asthma requiring daily use of a 
bronchodilator or inhaled/systemic corticosteroids, or other chronic lung diseases 
such as pulmonary fibrosis. 
6. 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. 
7. Has a current or previous diagnosis of immunocompromising condition, 
immune-mediated disease, or other immunosuppressive condition. 
8. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days 
in total within 6 months prior to Screening Visit (for corticosteroids ≥ 10 mg/day of 
prednisone or equivalent) or is anticipating the need for immunosuppressive treatment 
at any time during participation in the study. 
9. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the IP. 
10. Has a history of coagulopathy or bleeding disorder considered a contraindication to IM 
injection or phlebotomy. 
11. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP injection, 
with the exception of vaccines authorized or approved for the prevention of COVID-19 

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(regardless of type of vaccine) that become available to participants during the study. 
Efforts should be made to space study vaccination and COVID-19 vaccination by at 
least 7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
12. Has received a seasonal influenza vaccine or any other investigational influenza 
vaccine after 01 Jan 2021. 
13. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive them during the study. 
14. Has a diagnosis of malignancy within the previous 10 years (excluding nonmelanoma 
skin cancer). 
15. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
16. Has participated in an interventional clinical study within 28 days prior to the 
Screening Visit based on the medical history interview or plans to do so while 
participating in this study. 
17. Is an immediate family member or household member of study personnel, study site 
staff, or Sponsor personnel. 
Phase 2 NH and Phase 2 Extension Inclusion Criteria: 
Each participant must meet all of the following criteria at the Screening Visit and at Day 1, 
unless noted otherwise, to be enrolled in this study: 
1. Is an adult, ≥ 18 years of age at the time of consent (Screening Visit), who in the 
opinion of the Investigator, is medically stable based on review of medical history and 
physical examination performed at screening. Medically stable is defined as disease 
not requiring significant change in therapy or hospitalization for worsening disease 
during the 3 months before enrollment. Participants may be rescreened if they are not 
medically stable at the Screening Visit. 
2. Understands and is willing and physically able to comply with protocol-mandated 
follow-up, including all procedures, in the opinion of the Investigator. 
3. Has provided written informed consent for participation in this study, including all 
evaluations and procedures as specified in this protocol. 
4. If female and is not of childbearing potential, may be enrolled in the study. An FSH 
level may be measured at the discretion of the Investigator to confirm postmenopausal 
status (Section 11.2). 

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5. If female and of childbearing potential, meets all of the following criteria to be enrolled 
in the study: 
• Has a negative pregnancy test at the Screening Visit and 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. Adequate female 
contraception is defined as consistent and correct use of an FDA-approved 
contraceptive method in accordance with the product label. 
• Has agreed to continue adequate contraception through 3 months following vaccine 
administration. 
• Is not currently breastfeeding. 
Phase 2 NH Exclusion Criteria: 
Participant meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had close contact to someone with SARS-CoV-2 infection or COVID-19 as 
defined by the CDC in the past 14 days prior to the Screening Visit, unless the 
participant has been fully vaccinated for COVID-19. 
2. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 
the 28-day screening window and will retain their initially assigned participant 
number. 
3. Has a medical, psychiatric, occupational condition, or history of substance abuse 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. 
4. Has a current or previous diagnosis of immunocompromising/immunosuppressive 
condition, immune-mediated disease requiring immune-modifying therapy, asplenia, 
recurrent severe infections (human immunodeficiency virus [HIV]-positive participants 
on antiretroviral therapy with cluster of differentiation [CD] 4 count ≥ 350 cells/mm3 
and HIV-RNA ≤ 500 copies/mL within the past 12 months are permitted). 
5. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days 
in total within 6 months prior to Screening Visit (for corticosteroids ≥ 10 mg/day of 

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prednisone or equivalent) or is anticipating the need for systemic immunosuppressive 
treatment at any time during participation in the study. 
6. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the 
mRNA-1010 or the comparator vaccine, which is an egg-based influenza vaccine. 
7. Has coagulopathy or bleeding disorder considered a contraindication to IM injection or 
phlebotomy. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP injection, 
with the exception of vaccines authorized or approved for the prevention of COVID-19 
(regardless of type of vaccine) that become available to participants during the study. 
Efforts should be made to space study vaccination and COVID-19 vaccination by at 
least 7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
9. Has received a seasonal influenza vaccine or any other investigational influenza 
vaccine within 6 months prior to the Screening Visit. 
10. Had tested positive for influenza by CDC-recommended testing methods within 
6 months prior to the Screening Visit. 
11. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive them during the study. 
12. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
13. Has participated in an interventional clinical study within 28 days prior to the 
Screening Visit based on the medical history interview or plans to do so while 
participating in this study. 
14. Is an immediate family member or household member of study personnel, study site 
staff, or Sponsor personnel. 
Phase 2 Extension Exclusion Criteria: 
Participant meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had close contact to someone with SARS-CoV-2 infection or COVID-19 as 
defined by the CDC in the past 10 days prior to the Screening Visit. 

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2. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 
the 28-day screening window and will retain their initially assigned participant 
number. 
3. Has a medical, psychiatric, occupational condition, or history of substance abuse 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. 
4. Has a current or previous diagnosis of immunocompromising/immunosuppressive 
condition, immune-mediated disease requiring immune-modifying therapy, asplenia, 
recurrent severe infections (HIV-positive participants on antiretroviral therapy with 
CD 4 count ≥ 350 cells/mm3 and HIV-RNA ≤ 500 copies/mL within the past 365 days 
are permitted). 
5. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days 
in total within 180 days prior to Screening Visit (for corticosteroids ≥ 10 mg/day of 
prednisone or equivalent) or is anticipating the need for systemic immunosuppressive 
treatment at any time during participation in the study. 
6. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the 
mRNA-1010 or the comparator vaccine, which is an egg-based influenza vaccine. 
7. Has coagulopathy or bleeding disorder considered a contraindication to IM injection or 
phlebotomy. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP injection, 
with the exception of vaccines authorized or approved for the prevention of COVID-19 
(regardless of type of vaccine) that become available to participants during the study. 
Efforts should be made to space study vaccination and COVID-19 vaccination by at 
least 7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
9. Has received a seasonal influenza vaccine or any other investigational influenza 
vaccine within 180 days prior to the randomization visit. 
10. Had tested positive for influenza by CDC-recommended testing methods within 
180 days prior to the Screening Visit. 
11. Has received systemic immunoglobulins or blood products within 90 days prior to the 
Screening Visit or plans to receive them during the study. 

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12. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
13. Has participated in an interventional clinical study within 28 days prior to the 
Screening Visit based on the medical history interview or plans to do so while 
participating in this study. 
14. Is an immediate family member or household member of study personnel, study site 
staff, or Sponsor personnel. 
Study Treatments 
Investigational Product, Dosage, and Mode of Administration: 
Investigational products in the Phase 1/2 part of the study are the mRNA-1010 vaccine candidate 
and placebo. Investigational products administered in the Phase 2 NH and Phase 2 Extension 
parts of the study are the mRNA-1010 vaccine candidate and the licensed quadrivalent seasonal 
influenza vaccine (active comparator). 
In the Phase 1/2 part of the study, the mRNA-1010 vaccine to be tested includes mRNAs that 
encode for the surface glycoprotein HAs of the following influenza virus strains recommended 
by the WHO for 2020-2021 SH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Hong Kong/45/2019(H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
In the Phase 2 NH and Phase 2 Extension parts of the study, the mRNA-1010 vaccine to be 
tested includes mRNAs that encode for the surface glycoprotein HAs of the following influenza 
virus strains recommended by the WHO for 2021-2022 NH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Cambodia/e0826360/2020 (H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
mRNA-1010 is formulated in lipid nanoparticles composed of 4 lipids (1 proprietary and 
3 commercially available): the proprietary ionizable lipid SM-102 (heptadecan-9-yl 
8-((2-hydroxyethyl)(6-oxo-6-(undecyloxy)hexyl)amino)octanoate); 
cholesterol; 
1,2-distearoylsn-glycero-3-phosphocholine (DSPC); and 1 monomethoxypolyethyleneglycol-

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2,3-dimyristylglycerol with polyethylene glycol of average molecular weight 2000 
(PEG2000-DMG). The mRNA-1010 injection is provided as sterile liquid for injection and is a 
white to off-white dispersion at a concentration of 0.5 mg/mL (in the Phase 1/2 part) or 
0.4 mg/mL (in the Phase 2 NH and Phase 2 Extension parts) in 20 mM Tris buffer containing 
87 mg/mL sucrose and 10.7 mM sodium acetate at pH 7.5. 
In each part of the study, the mRNA-1010 vaccine will be administered as a single 0.5-mL IM 
injection at total dose levels ranging from 6.25 to 200 µg to participants according to the 
vaccination group assignment. 
The placebo (administered in Phase 1/2 part only) is 0.9% Sodium Chloride (normal saline) 
Injection, which meets the criteria of the US Pharmacopeia. 
The active comparator vaccine (administered in Phase 2 NH and Phase 2 Extension parts only) 
will be administered as a single 0.5 mL IM injection to participants per the vaccination group 
assignment. 

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Procedures and Assessments: 
Safety Assessments: 
Safety assessments will include monitoring and recording of the following for each participant: 
• Solicited local and systemic ARs that occur during the 7 days following vaccine 
administration (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 vaccine 
administration (ie, the day of injection and 27 subsequent days). 
• AEs leading to discontinuation from study participation from Day 1 through 
Day 181/EoS or withdrawal from the study. 
• MAAEs from Day 1 through Day 181/EoS or withdrawal from the study. 
• SAEs and AESIs from Day 1 through Day 181/EoS or withdrawal from the study. 
• Results of safety laboratory tests (Phase 1/2 part only). 
• Vital sign measurements. 
• Physical examination findings. 
• Assessments for causes of respiratory infections as needed from Day 1 through 
Day 181/EoS in the Phase 1/2 and Phase 2 Extension parts of the study or 
withdrawal from the study. Active and passive surveillance for ILI (and 
assessments for causes of respiratory infections as needed) will be conducted from 
Day 1 through Day 181/EoS in the Phase 2 NH part of the study.  
• Details of all pregnancies in female participants will be collected after the study 
vaccination on Day 1 and until the end of their participation in the study. 
• Optional blood sample collection on Day 4 in the Phase 2 Extension part. 
Immunogenicity Assessments: 
The following immunogenicity assessments are planned: 
• Serum antibody level as measured by hemagglutination inhibition (HAI) assay 
(primary, secondary, and exploratory endpoints). 
• Serum neutralizing antibody level as measured by microneutralization assay or 
similar method (secondary [Phase 1/2 part only] and exploratory endpoints). 

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• Cellular immunogenicity, in a subset of participants (Phase 1/2 cohort only), as 
assessed by flow cytometry/intracellular cytokine staining and/or enzyme-linked 
immune absorbent spot (exploratory endpoint). 
Statistical Methods: 
Hypothesis: 
No formal hypotheses will be tested. 
Sample Size: 
The sample size for this study 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 different dose levels of mRNA-1010. 
For the Phase 1/2 part of the study, approximately 180 participants will be randomly assigned 
in this study, with approximately 45 participants in each vaccination group. With 45 participants 
receiving an investigational vaccine, there is a probability of approximately 90% to observe at 
least 1 participant with an AE, if the true incidence rate of the AE is 5%; if the true incidence 
rate is 10%, then the probability to observe it will be approximately 99%. 
For the Phase 2 NH part of the study, approximately 500 participants will be randomly assigned 
in a 3:3:3:1 ratio to the mRNA-1010 25, 50, 100 µg groups, or the Active Comparator Group. 
A total of 450 participants will receive the mRNA-1010 vaccine (150 participants at each dose 
level). A sample size of 150 participants at each dose level has at least a 95% probability to 
observe at least 1 participant with an AE, if the true incidence rate is 2%; if the true incidence 
rate is 3%, then the probability to observe it will be 99%. 
For the Phase 2 Extension part of the study, approximately 200 participants will be randomly 
assigned in a 1:1:1:1 ratio to the mRNA-1010 6.25, 12.5, 25 µg groups, or the Active 
Comparator Group. A total of 150 participants will receive the mRNA-1010 vaccine 
(50 participants at each dose level). With 50 participants receiving an investigational vaccine, 
there is a probability of approximately 92% to observe at least 1 participant with an AE, if the 
true incidence rate of the AE is 5%; if the true incidence rate is 10%, then the probability to 
observe it will be approximately 99%. 
Analysis Sets: 
Set 
Description 
Randomization Set 
The Randomization Set consists of all participants who 
are randomly assigned. 

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Full Analysis Set (FAS)1 
The FAS consists of all randomly assigned participants 
who receive the IP. 
Per-Protocol (PP) Set2 
The PP Set consists of all participants in the FAS who 
comply with the injection schedule, comply with the 
timings of immunogenicity blood sampling to have a 
baseline and at least 1 postinjection assessment, do not 
have influenza infection at baseline through Day 29 (as 
documented by PCR testing), and have no major protocol 
deviations that impact the immune response. 
Safety Set3 
The Safety Set consists of all randomly assigned 
participants who receive the IP. 
Solicited Safety Set4 
The Solicited Safety Set consists of all participants in the 
Safety Set who contribute any solicited AR data. 
Abbreviations: AR = adverse reaction; IP = investigational product; PCR = polymerase chain reaction; RT-PCR = reverse 
transcription polymerase chain reaction. 
1. 
For the FAS, participants will be analyzed according to the group to which they were randomized. 
2. 
The PP Set will be used as the primary analysis set for analyses of immunogenicity unless otherwise specified. 
Participants will be analyzed according to the group to which they were randomized. 
3. 
The Safety Set will be used for all analyses of safety, except for the solicited ARs. Participants will be included in the 
vaccination group corresponding to what they actually received. 
4. 
The Solicited Safety Set will be used for the analyses of solicited ARs and participants will be included in the 
vaccination group corresponding to what they actually received. 
Safety Analyses: 
All safety analyses will be based on the Safety Set, except summaries of solicited ARs, which 
will be based on the Solicited Safety Set. All safety analyses will be provided by vaccination 
group. Participants will be included in the vaccination group corresponding to what 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 (including any clinical safety 
laboratory abnormalities [Phase 1/2 part only]), treatment-related AEs, severe AEs, SAEs, 
MAAEs, AEs leading to withdrawal from study participation, AESIs, vital sign measurements, 
and physical examination findings. 
The number and percentage of participants with any solicited local AR, solicited systemic AR, 
during the 7-day follow-up period after the injection will be summarized. A 2-sided 95% exact 
confidence interval (CI) using the Clopper-Pearson method will also be provided for the 
percentage of participants with any solicited AR. 
The number and percentage of participants with unsolicited AEs, treatment-related AEs, severe 
AEs, SAEs, AESIs, MAAEs, and AEs leading to withdrawal from study participation will be 
summarized. Unsolicited AEs will be coded according to the Medical Dictionary for Regulatory 

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Activities (MedDRA) for AR terminology and presented by MedDRA system organ class and 
preferred term. 
Solicited ARs will be coded according to the MedDRA for AR terminology. The toxicity 
grading scale for healthy adult and adolescent volunteers enrolled in preventive vaccine clinical 
trials will be used in this study with modification for rash, solicited ARs, and vital signs. 
Unsolicited AEs will be presented by MedDRA system organ class and preferred term. 
The number of events of unsolicited AEs/SAEs, AESIs, and MAAEs will be reported in 
summary tables accordingly. For all other safety parameters, descriptive summary statistics will 
be provided. 
Assessment of safety laboratory tests will be done for the Phase 1/2 part of the study only. The 
number and percentage of participants who have chemistry and hematology results below or 
above the normal laboratory ranges will be tabulated by time point. For treatment-emergent 
safety laboratory test results, the raw values and change from baseline values will be 
summarized by vaccination group and visit at each time point. 
For all parts of the study, vital sign results will also be presented. 
Immunogenicity Analyses: 
Immunogenicity analyses in each part of the study will be reported based on the Per-Protocol 
Set and provided by vaccination group, unless otherwise specified. 
Phase 1/2 
For the immunogenicity endpoints, geometric mean of specific antibody titers with 
corresponding 95% CI at each time point and geometric mean fold rise (GMFR) of specific 
antibody titers with corresponding 95% CI at each postbaseline time point over preinjection 
baseline at Day 1 will be provided by vaccination group. The 95% CIs will be calculated based 
on the t-distribution of the log 2-transformed values and then back transformed to the original 
scale. Descriptive summary statistics, including median, minimum, and maximum, will also be 
provided. 
For the calculation of geometric mean titers (GMTs), antibody titers reported as below the lower 
limit of quantification (LLOQ) will be replaced by 0.5 × LLOQ. Values that are greater than the 
upper limit of quantification (ULOQ) will be converted to the ULOQ. 
Seroconversion rate from baseline will be provided with a 2-sided 95% CI using the 
Clopper-Pearson method at each postbaseline time point. Rate of seroconversion is defined as 
the proportion of participants with either a prevaccination HAI titer < 1:10 and a postvaccination 

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HAI titer ≥ 1:40 or a prevaccination HAI titer ≥ 1:10 and a minimum 4-fold rise in the 
postvaccination HAI antibody titer. 
Phase 2 NH and Phase 2 Extension 
Immune responses, as measured by GMT and seroconversion rate in the mRNA-1010 groups 
based on Day 29 HAI titers, will be compared with that of participants receiving active 
comparator for all 4 strains. 
An analysis of covariance model will be carried out with HAI titers at Day 29 as a dependent 
variable and a group variable as the fixed variable. The GMT of the mRNA-1010 at Day 29 will 
be estimated by the geometric least square mean (GLSM) from the model. The geometric mean 
ratio (GMTr; ratio of GMT) will be estimated by the ratio of GLSM from the model. The 
corresponding 2-sided 95% CI will be provided to assess the difference in immune response 
between the mRNA-1010 compared with the active comparator at Day 29. 
The number and percentage of participants with seroconversion due to vaccination will 
be provided with 2-sided 95% CI using the Clopper-Pearson method at Day 29. The 
seroconversion rate difference with 95% CI at Day 29 will be provided. 
In addition, the GMT of HAI titers with corresponding 95% CI will be provided at each time 
point. The 95% CIs will be calculated based on the t-distribution of the log 2-transformed values 
and then back transformed to the original scale. The GMFR of HAI titers with corresponding 
95% CI at each postbaseline time point over baseline will be provided. Descriptive summary 
statistics, including median, minimum, and maximum, will also be provided. 
For summarizations of GMTs, antibody titers reported as LLOQ will be replaced by 
0.5 × LLOQ. Values that are greater than ULOQ will be converted to the ULOQ. 
Rate of seroconversion is defined as (1) if LLOQ is 1:10, the proportion of participants with 
either a prevaccination HAI titer < 1:10 and a postvaccination HAI titer ≥ 1:40 or a 
prevaccination HAI titer ≥ 1:10 and a minimum 4-fold rise in the postvaccination HAI antibody 
titer; or (2) if LLOQ is greater than 1:10, the proportion of participants with either a 
prevaccination HAI titer < LLOQ and a postvaccination HAI ≥ 4 times of LLOQ, or a 
prevaccination HAI ≥ LLOQ and a minimum 4-fold rise in the postvaccination HAI . 
The HAI titers at Day 29, GMTr at Day 29, and the difference in seroconversion rate at Day 29 
may also be performed with the Full Analysis Set as supplementary analyses. 

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Phase 2 Extension 
Immune responses, as measured by GMT and seroconversion rate in the mRNA-1010 groups 
based on Day 29 HAI titers, will be compared with that of participants receiving active 
comparator for all 4 strains. 
The number and percentage of participants with seroconversion due to vaccination will 
be provided with 2-sided 95% CI using the Clopper-Pearson method at Day 29. The 
seroconversion rate difference with 95% CI at Day 29 will be provided. 
For summarizations of GMTs, antibody titers reported as LLOQ will be replaced by 
0.5 × LLOQ. Values that are greater than ULOQ will be converted to the ULOQ. The definition 
of rate of seroconversion will be the same definition as the rate of seroconversion in Phase 2 
NH. 
Study Analyses 
A Day 29 IA is planned in this study for the Phase 1/2, Phase 2 NH, and Phase 2 Extension parts 
separately. The IA for the Phase 1/2 part will be performed after all participants have completed 
the Day 29 Visit. All relevant data to the IA will be cleaned (ie, data that are as clean as possible). 
For the Phase 2 NH and the Phase 2 Extension parts, an IA of safety (reactogenicity and 
immunogenicity as applicable) will be performed after participants have completed the Day 29 
Visit for each part of the study. All data relevant to the IA through the Day 29 Visit will be 
cleaned (ie, data that are as clean as possible). An interim study report may be generated, in 
which case a formal database lock will be performed to support the interim study report. 
The IAs will be performed by a separate team of unblinded programmers and statisticians. The 
analyses will be presented by vaccination groups. Except for a limited number of Sponsor and 
CRO personnel who will be unblinded to perform the IA, the study site staff, Investigators, study 
monitors, and participants will remain blinded until after the final database lock for final 
analysis. 
The final analysis of safety, reactogenicity, and immunogenicity will be performed after all 
participants have completed all planned study procedures. The results of this analysis will be 
presented in a final clinical study report, including individual listings. 
 

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1.2. 
Schema 
Figure 1 Phase 1/2 - Study Schema 
 
Abbreviations: DSMB = Data and Safety Monitoring Board; IST = internal safety team; N = number of participants. 
1 Expansion from the initial stage to the expansion stage is triggered by the IST. 
 

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Figure 2 Phase 2 Northern Hemisphere - Study Schema 
 
 
Abbreviations: DSMB = Data and Safety Monitoring Board; N = number of participants. 
Figure 3 Phase 2 Extension - Study Schema 
 
Abbreviations: DSMB = Data and Safety Monitoring Board; N = number of participants. 

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1.3. 
Schedule of Events 
Table 1 
Phase 1/2 - Schedule of Events 
Visit Number 
SCRN1 
1 
2 
3 
4 
5, 6, and 
7 
8 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
C 
SC 
C 
C 
Month Time Point 
NA 
M0 
M0 
M1 
M2 
M3-M5 
M6 
M0-M6 
Study Visit Day  
- 
D1 
(Baseline) 
D8 
D29 
D57 
D91, 
D121, 
D151 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
–2 or +1 
±2 
±5 
±5 
±14 
NA 
ICF, demographics, concomitant medications, 
medical history  
X 
- 
- 
- 
- 
- 
- 
- 
Inclusion/exclusion criteria 
X 
X 
- 
- 
- 
- 
- 
- 
Blood collection for safety laboratory samples2 
X 
- 
X 
- 
- 
- 
- 
- 
Physical examination3 
X 
- 
- 
- 
- 
- 
- 
- 
Vital signs4 
X 
X 
- 
- 
- 
- 
- 
- 
Pregnancy testing5 
X 
X 
- 
- 
- 
- 
- 
- 
Randomization 
- 
X 
- 
- 
- 
- 
- 
- 
Study vaccination (including 60-minute postdosing 
observation period) 
- 
X6 
- 
- 
- 
- 
- 
- 
Blood collection for humoral immunogenicity7 
- 
X 
X 
X 
- 
- 
X 
- 
Blood collection for cellular immunogenicity7 
- 
X 
X 
X 
- 
- 
- 
- 
NP swab for virus detection8 
- 
X 
- 
- 
- 
- 
- 
X 
eDiary activation for recording solicited ARs 
(7 days)9 
- 
X 
- 
- 
- 
- 
- 
- 
Review of eDiary 
- 
- 
X 
- 
- 
- 
- 
- 
Follow-up safety calls10 
- 
- 
- 
- 
- 
X 
- 
- 
Recording of unsolicited AEs 
- 
X 
X 
X 
- 
- 
- 
- 

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Visit Number 
SCRN1 
1 
2 
3 
4 
5, 6, and 
7 
8 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
C 
SC 
C 
C 
Month Time Point 
NA 
M0 
M0 
M1 
M2 
M3-M5 
M6 
M0-M6 
Study Visit Day  
- 
D1 
(Baseline) 
D8 
D29 
D57 
D91, 
D121, 
D151 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
–2 or +1 
±2 
±5 
±5 
±14 
NA 
Recording of MAAEs and concomitant medications 
relevant to or for the treatment of the MAAE11 
- 
X 
X 
X 
X 
X 
X 
X 
Recording of SAEs, AESIs, and concomitant 
medications relevant to or for the treatment of the 
SAE and/or AESI11 
- 
X 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and nonstudy 
vaccinations11 
X 
X 
X 
X 
X 
X 
X 
X 
Phase 1/2 completion 
- 
- 
- 
- 
- 
- 
X 
- 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; ALT = alanine aminotransferase; AR = adverse reaction; AST = aspartate aminotransferase; 
C = clinic visit (ie, study site visit); COVID-19 = coronavirus disease 2019; D = day; eCRF = electronic case report form; eDiary = electronic diary; EoS = end of study; 
FSH = follicle-stimulating hormone; ICF = informed consent form; ILI = influenza-like illness; IM = intramuscular; IP = investigational product; M = month; 
MAAE = medically attended adverse event; NA = not applicable; NP = nasopharyngeal; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse 
event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety call (phone or contact by electronic means); SCRN = screening; WBC = white blood cell. 
1 The Screening Visit and Day 1 Visit cannot be completed on the same day. Additionally, the Screening Visit may be performed over multiple visits if within the 28-day screening 
window. 
2 Safety laboratory tests: WBC count, hemoglobin, platelets, ALT, AST, total bilirubin, alkaline phosphatase, and creatinine. 
3 Physical examination: A full physical examination, including height and weight, will be performed at screening. 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. 
4 Vital sign measurement: systolic and diastolic blood pressure, heart rate, respiratory rate, and body temperature. Participants will be seated for at least 5 minutes before all 
measurements are taken. Vital signs will be collected at the Screening Visit and on the day of vaccination, once before and at least 1 hour after the vaccination. Vital signs will be 
collected at other study site visits only in conjunction with a symptom-directed physical examination. The preferred route of temperature assessment is oral. Participants must not 
eat or drink anything hot or cold within 10 minutes before oral temperature is taken. If any of the vital sign measurements meet the toxicity grading criteria for clinical 
abnormalities of Grade 3 or greater, the abnormal value and grade will be documented in the AE section of the eCRF (unless there is another known cause of the abnormality that 
would result in an AE classification). The Investigator will continue to monitor the participant with additional assessments until the vital sign value has reached the reference 
range, returns to the vital sign value at baseline, is considered stable or until the Investigator determines that follow-up is no longer medically necessary. 
5 A point-of-care urine pregnancy test will be performed at the Screening Visit and before the vaccine dose on Day 1. At the discretion of the Investigator, a pregnancy test either 
via blood or point-of-care urine can be performed at any time. The FSH level may be measured at the Screening Visit as necessary and at the discretion of the Investigator to 
confirm postmenopausal status. 

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6 A 50-µg dose of mRNA-1010 will be administered for Vaccination Group 1, a 100-µg dose of mRNA-1010 will be administered for Vaccination Group 2, a 200-µg dose of 
mRNA-1010 will be administered for Vaccination Group 3, and placebo will be administered for Vaccination Group 4. All participants will receive a single 0.5-mL IM injection 
of the IP. 
7 Samples for humoral and cellular immunogenicity (and safety laboratory samples) must be collected prior to receipt of vaccination on Day 1. Cellular immunogenicity samples 
will be collected from approximately 40 participants per vaccination group and assessed in a subset. 
8 An NP swab specimen will be collected on Day 1 prior to vaccination to assess for asymptomatic infection with respiratory pathogens, including influenza virus and 
SARS-CoV-2. An NP swab will also be collected at any time during the study through study completion if any signs or symptoms or an MAAE suggesting COVID-19 or ILI 
occur, to confirm the diagnosis by RT-PCR. For signs or symptoms during the study, a participant will be instructed to contact the study site to have an NP swab collected for 
testing for respiratory pathogens at an unscheduled visit. The NP swabs may be collected as part of a home visit in lieu of a study site visit.  
9 The eDiary entries will be recorded by the participant at approximately 1 hour after vaccination while at the study site under the supervision of the study site staff. Participants 
will continue to record data in the eDiary for solicited AEs each day 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. Any solicited AR that continues beyond Day 7 will be reported until it is no longer reported but only until 28 days after vaccination. 
Adverse reactions recorded in diaries beyond Day 7 should be reviewed either during the next scheduled telephone call or at the next study site visit. 
10 Trained study personnel will call all participants to collect information relating to any AEs, MAAEs, AEs leading to withdrawal from study participation, SAEs, AESIs, 
information on concomitant medications associated with those events, and any nonstudy vaccinations. 
11 All nonstudy vaccinations will be recorded through Day 181/EoS. All concomitant medications will be recorded through 28 days after vaccination; all concomitant medications 
relevant to or for the treatment of an SAE, AESI, or MAAE will be recorded from Day 1 through Day 181/EoS. 
 

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Table 2 
Phase 2 Northern Hemisphere - Schedule of Events 
Visit Number 
SCRN1 
1 
2 
3 
4 
5 
6 
Unscheduled 
Type of Visit/Contact 
C 
C 
SC 
SC 
C 
C 
C 
C 
Month Time Point 
NA 
M0 
M0 
M0 
M1 
M3 
M6 
M0-M6 
Study Visit Day  
- 
D1 
(Baseline) 
D8 
D15 
D29 
D91 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
±3 
±3 
-7 to 
+3 
±5 
±14 
NA 
ICF, demographics, concomitant medications, 
medical history2 
X 
- 
- 
- 
- 
- 
- 
- 
Inclusion/exclusion criteria 
X 
X 
- 
- 
- 
- 
- 
- 
Physical examination3 
X 
- 
- 
- 
- 
- 
- 
- 
Vital signs4 
X 
X 
- 
- 
- 
- 
- 
- 
Pregnancy testing5 
X 
X 
- 
- 
- 
- 
- 
- 
Randomization 
- 
X 
- 
- 
- 
- 
- 
- 
Study vaccination (including 60-minute postdosing 
observation period) 
- 
X6 
- 
- 
- 
- 
- 
- 
Blood collection for humoral immunogenicity (and 
exploratory assessments)7 
- 
X 
- 
- 
X 
X 
X 
- 
Optional blood collection for pharmacogenomics 
- 
X 
- 
- 
- 
- 
- 
- 
NP swab for virus detection8 
- 
- 
- 
- 
- 
- 
- 
X 
eDiary activation for recording solicited ARs 
(7 days)9 
- 
X 
- 
- 
- 
- 
- 
- 
Review of eDiary for solicited ARs 
- 
- 
X 
- 
- 
- 
- 
- 
eDiary activation for active and passive 
surveillance10 
- 
X 
- 
- 
- 
- 
- 
- 
eDiary active surveillance collection of symptoms of 
ILI11 
- 
3 to 4 times weekly 
Twice weekly 
- 

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Visit Number 
SCRN1 
1 
2 
3 
4 
5 
6 
Unscheduled 
Type of Visit/Contact 
C 
C 
SC 
SC 
C 
C 
C 
C 
Month Time Point 
NA 
M0 
M0 
M0 
M1 
M3 
M6 
M0-M6 
Study Visit Day  
- 
D1 
(Baseline) 
D8 
D15 
D29 
D91 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
±3 
±3 
-7 to 
+3 
±5 
±14 
NA 
eDiary passive surveillance collection of symptoms 
of ILI11 
- 
X 
- 
Review of eDiary12 
- 
Review participant-recorded ILI starting on Day 1 through Day 181/EoS 
Follow-up safety call 
- 
- 
X 
X 
- 
- 
- 
- 
Recording of unsolicited AEs 
- 
X 
X 
X 
X 
- 
- 
- 
Recording of MAAEs and concomitant medications 
relevant to or for the treatment of the MAAE13 
- 
X 
X 
X 
X 
X 
X 
X 
Recording of SAEs, AESIs, and concomitant 
medications relevant to or for the treatment of the 
SAE and/or AESI13 
- 
X 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and nonstudy 
vaccinations14 
X 
X 
X 
X 
X 
X 
X 
X 
Study completion 
- 
- 
- 
- 
- 
- 
X15 
- 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; C = clinic visit (ie, study site visit); COVID-19 = coronavirus disease 2019; 
D = day; eCRF = electronic case report; form; eDiary = electronic diary; EoS = end of study; FSH = follicle-stimulating hormone; ICF = informed consent form; 
ILI = influenza-like illness; IM = intramuscular; M = month; MAAE = medically attended adverse event; NA = not applicable; NP = nasopharyngeal swab; SAE = serious 
adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety call (phone or contact by electronic means); SCRN = screening. 
1 The Screening Visit and Day 1 Visit may be performed on the same day or a different day. Additionally, the Screening Visit may be performed over multiple visits if within the 
28-day screening window. 
2 Verbal confirmation of medical history is acceptable. 
3 Physical examination: A full physical examination, including height and weight, will be performed at screening; symptom-directed physical examinations will be performed at all 
other clinic visits (ie, study site visits). Interim physical examinations will be performed at the discretion of the Investigator. Any clinically significant finding identified by a 
healthcare professional during study visits should be reported as an MAAE. 
4 Vital sign measurement: Systolic and diastolic blood pressure, heart rate, respiratory rate, and body temperature. The preferred route of temperature assessment is oral. 
Participants must not eat or drink anything hot or cold within 10 minutes before oral temperature is taken. Participants will be seated for at least 5 minutes before all 
measurements are taken. Vital signs will be collected on the day of vaccination, once before vaccination and approximately 1 hour after vaccination. Vital signs may be collected 
at other study site visits in conjunction with a symptom-directed physical examination. If any of the vital sign measurements meet the toxicity grading criteria for clinical 

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abnormalities of Grade 3 or greater, the abnormal value and grade will be documented in the AE section of the eCRF (unless there is another known cause of the abnormality that 
would result in an AE classification). The Investigator will continue to monitor the participant with additional assessments until the vital sign value has reached the reference 
range, returns to the vital sign value at baseline, is considered stable or until the Investigator determines that follow-up is no longer medically necessary. 
5 A point-of-care urine pregnancy test will be performed at the Screening Visit (and before the vaccine dose on Day 1 if Day 1 is not on the same day as the Screening Visit). At the 
discretion of the Investigator, a pregnancy test either via blood or point-of-care urine can be performed at any time. The FSH level may be measured at the Screening Visit as 
necessary and at the discretion of the Investigator, to confirm postmenopausal status. 
6 See Table 8 for dose levels and vaccination groups. All participants will be randomized to receive a single 0.5-mL IM injection. 
7 Samples for humoral immunogenicity (and exploratory assessments) must be collected prior to receipt of vaccination on Day 1. A subset of samples collected will be assessed for 
humoral immunogenicity (and exploratory assessments). 
8 An NP swab specimen for pathogens, including influenza virus and SARS-CoV-2 will be collected any time from Day 1 through Day 181/EoS if participants have 
protocol-defined ILI or symptoms suggestive of COVID-19 or other upper or lower respiratory infection at the Investigator’s discretion. If participants experience these 
symptoms/signs, they will be instructed to contact the study site to have an NP swab collected for testing. The NP swabs may be collected as part of a home visit in lieu of a 
study site visit.  
9 The eDiary entries will be recorded by all participants at approximately 1 hour after vaccination while at the study site under the supervision of the study site staff. Participants 
will continue to record data in the eDiary for solicited ARs each day after they leave the study site, preferably in the evening and at the same time each day, on the day of 
vaccination, and the 6 days following vaccination. Any solicited AR that is ongoing beyond Day 7 will be reported until it is no longer reported but only until 28 days after 
vaccination. Adverse reactions recorded in the eDiary beyond Day 7 should be reviewed either during the next scheduled call or study site visit, or during an unscheduled visit. 
10 The eDiary will be activated for collection of ILI symptoms. 
11 Passive Surveillance: Participants will be instructed to report symptoms of ILI any time from Day 1 through Day 181/EoS; Active Surveillance: Participants will be instructed to 
report whether ILI symptoms have been experienced, 3 to 4 times weekly from Day 1 through Day 29 and twice weekly from Day 30 through Day 181/EoS, via eDiary or 
telephone calls. If symptoms occur, participants will be directed to return to the study site as soon as possible, but no later than 72 hours after the onset of symptoms for medical 
evaluation and an NP swab. 
12 Review of eDiary for recording of symptoms of ILI. 
13 Trained study personnel will call all participants to collect information relating to any MAAEs, AEs leading to study discontinuation, SAEs, AESIs, information on concomitant 
medications associated with those events, and any nonstudy vaccinations. 
14 All nonstudy vaccinations will be recorded through Day 181/EoS. All concomitant medications will be recorded through 28 days after vaccination; all concomitant medications 
relevant to or for the treatment of an SAE, AESI, or MAAE will be recorded from Day 1 through Day 181/EoS. 
15 Participants who develop ILI will be followed through 30 days from the onset of ILI even if Day 30 is beyond Day 181/EoS. 
 
 

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Protocol: mRNA-1010-P101 Amendment 4 
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Table 3 
Phase 2 Extension - Schedule of Events 
Visit Number 
SCRN1 
1 
2 
3 
4 
5 
6 
7 
Unscheduled 
Type of Visit/Contact 
C 
C 
C 
SC 
SC 
C 
C 
C 
C 
Month Time Point 
NA 
M0 
M0 
M0 
M0 
M1 
M3 
M6 
M0-M6 
Study Visit Day 
- 
D1 
(Baseline) 
D4 
D8 
D15 
D29 
D91 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
-2 
±3 
±3 
-7 to 
+3 
±5 
±14 
NA 
ICF, demographics, concomitant medications, 
medical history2 
X 
- 
- 
- 
- 
- 
- 
- 
- 
Inclusion/exclusion criteria 
X 
X 
- 
- 
- 
- 
- 
- 
- 
Physical examination3 
X 
- 
- 
- 
- 
- 
- 
- 
- 
Vital signs4 
X 
X 
- 
- 
- 
- 
- 
- 
- 
Pregnancy testing5 
X 
X 
- 
- 
- 
- 
- 
- 
- 
Randomization 
- 
X 
- 
- 
- 
- 
- 
- 
- 
Study vaccination (including 60-minute postdosing 
observation period) 
- 
X6 
- 
- 
- 
- 
- 
- 
- 
Blood collection for humoral immunogenicity (and 
exploratory assessments)7 
- 
X 
- 
- 
- 
X 
X 
X 
- 
Optional blood collection for pharmacogenomics 
- 
X 
- 
- 
- 
- 
- 
- 
- 
Optional blood collection for potential biomarker 
analysis8 
- 
- 
X 
- 
- 
- 
- 
- 
- 
NP swab for virus detection9 
- 
- 
- 
- 
- 
- 
- 
- 
X 
eDiary activation for recording solicited ARs 
(7 days)10 
- 
X 
- 
- 
- 
- 
- 
- 
- 
Review of eDiary for solicited ARs 
- 
- 
- 
X 
- 
- 
- 
- 
- 
Follow-up safety call 
- 
- 
- 
X 
X 
- 
- 
- 
- 
Recording of unsolicited AEs 
- 
X 
- 
X 
X 
X 
- 
- 
- 

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Visit Number 
SCRN1 
1 
2 
3 
4 
5 
6 
7 
Unscheduled 
Type of Visit/Contact 
C 
C 
C 
SC 
SC 
C 
C 
C 
C 
Month Time Point 
NA 
M0 
M0 
M0 
M0 
M1 
M3 
M6 
M0-M6 
Study Visit Day 
- 
D1 
(Baseline) 
D4 
D8 
D15 
D29 
D91 
D181/EoS 
NA 
Window Allowance (Days) 
-28 
- 
-2 
±3 
±3 
-7 to 
+3 
±5 
±14 
NA 
Recording of MAAEs and concomitant medications 
relevant to or for the treatment of the MAAE11 
- 
X 
- 
X 
X 
X 
X 
X 
X 
Recording of SAEs, AESIs, and concomitant 
medications relevant to or for the treatment of the 
SAE and/or AESI11 
- 
X 
- 
X 
X 
X 
X 
X 
X 
Recording of concomitant medications and nonstudy 
vaccinations12 
X 
X 
- 
X 
X 
X 
X 
X 
X 
Study completion 
- 
- 
- 
- 
- 
- 
- 
X13 
- 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; C = clinic visit (ie, study site visit); COVID-19 = coronavirus disease 2019; 
D = day; eCRF = electronic case report; form; eDiary = electronic diary; EoS = end of study; FSH = follicle-stimulating hormone; ICF = informed consent form; 
ILI = influenza-like illness; IM = intramuscular; M = month; MAAE = medically attended adverse event; NA = not applicable; NP = nasopharyngeal swab; SAE = serious 
adverse event; SARS-CoV-2 = severe acute respiratory syndrome coronavirus 2; SC = safety call (phone or contact by electronic means); SCRN = screening. 
1 The Screening Visit and Day 1 Visit may be performed on the same day or a different day. Additionally, the Screening Visit may be performed over multiple visits if within the 
28-day screening window. 
2 Verbal confirmation of medical history is acceptable. 
3 Physical examination: A full physical examination, including height and weight, will be performed at screening; symptom-directed physical examinations will be performed at all 
other clinic visits (ie, study site visits). Interim physical examinations will be performed at the discretion of the Investigator. Any clinically significant finding identified by a 
healthcare professional during study visits should be reported as an MAAE. 
4 Vital sign measurement: Systolic and diastolic blood pressure, heart rate, respiratory rate, and body temperature. The preferred route of temperature assessment is oral. 
Participants must not eat or drink anything hot or cold within 10 minutes before oral temperature is taken. Participants will be seated for at least 5 minutes before all 
measurements are taken. Vital signs will be collected on the day of vaccination, once before vaccination and approximately 1 hour after vaccination. Vital signs may be collected 
at other study site visits in conjunction with a symptom-directed physical examination. If any of the vital sign measurements meet the toxicity grading criteria for clinical 
abnormalities of Grade 3 or greater, the abnormal value and grade will be documented in the AE section of the eCRF (unless there is another known cause of the abnormality that 
would result in an AE classification). The Investigator will continue to monitor the participant with additional assessments until the vital sign value has reached the reference 
range, returns to the vital sign value at baseline, is considered stable or until the Investigator determines that follow-up is no longer medically necessary. 
5 A point-of-care urine pregnancy test will be performed at the Screening Visit (and before the vaccine dose on Day 1 if Day 1 is not on the same day as the Screening Visit). At the 
discretion of the Investigator, a pregnancy test either via blood or point-of-care urine can be performed at any time. The FSH level may be measured at the Screening Visit as 
necessary and at the discretion of the Investigator, to confirm postmenopausal status. 
6 See Table 9 for dose levels and vaccination groups. All participants will be randomized to receive a single 0.5-mL IM injection. 

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7 Samples for humoral immunogenicity (and exploratory assessments) must be collected prior to receipt of vaccination on Day 1. A subset of samples collected will be assessed for 
humoral immunogenicity (and exploratory assessments). 
8 Biomarker plasma and biomarker serum samples will be stored for potential future biomarker assessment. 
9An NP swab specimen for pathogens, including influenza virus and SARS-CoV-2 will be collected any time from Day 1 through Day 181/EoS if participants experience 
symptoms consistent with the US CDC definition of ILI and/or symptoms suggestive of COVID-19 or other upper or lower respiratory infection at the Investigator’s discretion. 
If participants experience these symptoms/signs, they will be instructed to contact the study site to have an NP swab collected for testing. The NP swabs may be collected as part 
of a home visit in lieu of a study site visit. In the event that NP swabs during ILI cannot be collected, any available influenza and/or SARS-CoV-2 testing results performed 
outside of the study should be captured in the eCRF. 
10 The eDiary entries will be recorded by all participants at approximately 1 hour after vaccination while at the study site under the supervision of the study site staff. Participants 
will continue to record data in the eDiary for solicited ARs each day after they leave the study site, preferably in the evening and at the same time each day, on the day of 
vaccination, and the 6 days following vaccination. Any solicited AR that is ongoing beyond Day 7 will be reported until it is no longer reported but only until 28 days after 
vaccination. Adverse reactions recorded in the eDiary beyond Day 7 should be reviewed either during the next scheduled call or study site visit, or during an unscheduled visit. 
11 Trained study personnel will call all participants to collect information relating to any MAAEs, AEs leading to study discontinuation, SAEs, AESIs, information on concomitant 
medications associated with those events, and any nonstudy vaccinations. 
12 All nonstudy vaccinations will be recorded through Day 181/EoS. All concomitant medications will be recorded through 28 days after vaccination; all concomitant medications 
relevant to or for the treatment of an SAE, AESI, or MAAE will be recorded from Day 1 through Day 181/EoS. 
13 Participants who develop ILI will be followed through 30 days from the onset of ILI even if Day 30 is beyond Day 181/EoS. 
 

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TABLE OF CONTENTS 
 
CLINICAL STUDY PROTOCOL ..................................................................................................1 
PROTOCOL APPROVAL – SPONSOR SIGNATORY ................................................................2 
DECLARATION OF INVESTIGATOR .........................................................................................3 
PROTOCOL AMENDMENT SUMMARY OF CHANGES ..........................................................4 
1. 
PROTOCOL SUMMARY ............................................................................................7 
1.1. 
Synopsis ........................................................................................................................7 
1.2. 
Schema ........................................................................................................................31 
1.3. 
Schedule of Events .....................................................................................................33 
TABLE OF CONTENTS ...............................................................................................................42 
LIST OF TABLES .........................................................................................................................46 
LIST OF FIGURES .......................................................................................................................47 
LIST OF ABBREVIATIONS AND DEFINITION OF TERMS ..................................................48 
2. 
INTRODUCTION ......................................................................................................51 
2.1. 
Study Rationale ...........................................................................................................51 
2.2. 
Background and Overview .........................................................................................51 
2.2.1. 
mRNA-1010 ...............................................................................................................51 
2.2.2. 
Nonclinical Studies .....................................................................................................52 
2.2.3. 
Clinical Studies ...........................................................................................................53 
2.3. 
Benefit/Risk Assessment ............................................................................................53 
2.3.1. 
Known Potential Benefits ...........................................................................................53 
2.3.2. 
Risks From Study Participation and Their Mitigation ................................................54 
2.3.3. 
Overall Benefit/Risk Conclusion ................................................................................55 
3. 
OBJECTIVES AND ENDPOINTS ............................................................................56 
3.1. 
Phase 1/2 .....................................................................................................................56 
3.2. 
Phase 2 Northern Hemisphere and Phase 2 Extension ...............................................57 
4. 
STUDY DESIGN .......................................................................................................60 
4.1. 
General Design ...........................................................................................................60 
4.2. 
Scientific Rationale for Study Design ........................................................................66 
4.3. 
Choice of Vaccine Dose .............................................................................................67 
4.4. 
End of Study Definition ..............................................................................................68 

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5. 
STUDY POPULATION .............................................................................................69 
5.1. 
Phase 1/2 .....................................................................................................................69 
5.1.1. 
Inclusion Criteria ........................................................................................................69 
5.1.2. 
Exclusion Criteria .......................................................................................................70 
5.2. 
Phase 2 Northern Hemisphere and Phase 2 Extension ...............................................72 
5.2.1. 
Inclusion Criteria ........................................................................................................72 
5.2.2. 
Phase 2 Northern Hemisphere Exclusion Criteria ......................................................73 
5.2.3. 
Phase 2 Extension Exclusion Criteria .........................................................................74 
5.3. 
Lifestyle Restrictions ..................................................................................................75 
5.4. 
Screen Failures ............................................................................................................76 
6. 
STUDY TREATMENT ..............................................................................................77 
6.1. 
Investigational Products Administered .......................................................................77 
6.2. 
Randomization ............................................................................................................79 
6.2.1. 
Phase 1/2 .....................................................................................................................79 
6.2.2. 
Phase 2 Northern Hemisphere ....................................................................................79 
6.2.3. 
Phase 2 Extension .......................................................................................................79 
6.3. 
Preparation/Handling/Storage/Accountability ............................................................79 
6.3.1. 
Preparation of Investigational Product .......................................................................79 
6.3.2. 
Investigational Product Administration ......................................................................80 
6.3.3. 
Investigational Product Delivery and Receipt ............................................................80 
6.3.4. 
Investigational Product Packaging and Labeling .......................................................81 
6.3.5. 
Investigational Product Storage ..................................................................................81 
6.3.6. 
Investigational Product Accountability ......................................................................82 
6.3.7. 
Investigational Product Handling and Disposal .........................................................82 
6.4. 
Investigational Product Compliance ...........................................................................82 
6.5. 
Prior and Concomitant Medications ...........................................................................82 
6.5.1. 
Prior Medications and Therapies ................................................................................82 
6.5.2. 
Concomitant Medications and Therapies ...................................................................83 
6.5.3. 
Concomitant Medications and Vaccines That May Lead to the Elimination of 
a Participant From Per-Protocol Analyses ...................................................................84 
6.6. 
Intervention After End of the Study ...........................................................................84 
7. 
DELAY OR DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL .......................................85 

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7.1. 
Pause Rules .................................................................................................................85 
7.1.1. 
Pause Rules for the Phase 1/2 Part of the Study .........................................................85 
7.1.2. 
Pause Rules for the Phase 2 Northern Hemisphere and the Phase 2 Extension 
Parts of the Study ........................................................................................................86 
7.2. 
Criteria for Delay or Withholding of Study Vaccination ...........................................87 
7.3. 
Participant Discontinuation/Withdrawal From the Study ...........................................88 
7.4. 
Lost to Follow-Up.......................................................................................................89 
8. 
STUDY ASSESSMENTS AND PROCEDURES ......................................................90 
8.1. 
Safety Assessments and Procedures ...........................................................................91 
8.1.1. 
Use of Electronic Diaries ............................................................................................91 
8.1.2. 
Safety Telephone Calls ...............................................................................................93 
8.1.3. 
Safety Laboratory Assessments ..................................................................................93 
8.1.4. 
Vital Sign Measurements ............................................................................................94 
8.1.5. 
Physical Examinations ................................................................................................94 
8.1.6. 
Assessments for Respiratory Viral Infections ............................................................95 
8.2. 
Immunogenicity Assessments ....................................................................................96 
8.3. 
Efficacy Assessments .................................................................................................97 
8.4. 
Safety Definitions and Related Procedures ................................................................97 
8.4.1. 
Adverse Event .............................................................................................................97 
8.4.2. 
Serious Adverse Events ..............................................................................................98 
8.4.3. 
Solicited Adverse Reactions .......................................................................................99 
8.4.4. 
Medically Attended Adverse Events ........................................................................101 
8.4.5. 
Anaphylaxis ..............................................................................................................102 
8.4.6. 
Influenza-Like Illness ...............................................................................................103 
8.4.7. 
Adverse Events of Special Interest ...........................................................................103 
8.4.8. 
Recording and Follow-Up of Pregnancy ..................................................................104 
8.4.9. 
Eliciting and Documenting Adverse Events .............................................................104 
8.4.10. 
Assessment of Intensity ............................................................................................105 
8.4.11. 
Assessment of Causality ...........................................................................................105 
8.4.12. 
Reporting Adverse Events ........................................................................................106 
8.4.13. 
Reporting Serious Adverse Events ...........................................................................106 
8.4.14. 
Reporting of Adverse Events of Special Interest ......................................................107 

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8.4.15. 
Time Period and Frequency for Collecting Adverse Event and Serious 
Adverse Event Information .......................................................................................107 
8.4.16. 
Method of Detecting Adverse Events and Serious Adverse Events .........................108 
8.4.17. 
Follow-Up of Adverse Events and Serious Adverse Events ....................................109 
8.4.18. 
Regulatory Reporting Requirements for Serious Adverse Events ...........................109 
8.5. 
Safety Monitoring .....................................................................................................109 
8.6. 
Treatment of Overdose .............................................................................................109 
8.7. 
Pharmacokinetics ......................................................................................................109 
8.8. 
Pharmacodynamics ...................................................................................................109 
8.9. 
Biomarkers ................................................................................................................110 
8.10. 
Health Economics .....................................................................................................110 
9. 
STATISTICAL ANALYSIS PLAN .........................................................................111 
9.1. 
Blinding and Responsibility for Analyses ................................................................111 
9.1.1. 
Breaking the Blind ....................................................................................................112 
9.2. 
Statistical Hypotheses ...............................................................................................112 
9.3. 
Sample Size Determination ......................................................................................112 
9.4. 
Analysis Sets .............................................................................................................114 
9.5. 
Statistical Methods ....................................................................................................114 
9.5.1. 
Baseline Characteristics and Demographics .............................................................114 
9.5.2. 
Safety Analyses ........................................................................................................114 
9.5.3. 
Immunogenicity Analyses ........................................................................................116 
9.5.4. 
Exploratory Analyses ................................................................................................118 
9.5.5. 
Subgroup Analyses ...................................................................................................118 
9.6. 
Study Analyses .........................................................................................................118 
10. 
REFERENCES .........................................................................................................119 
11. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS ................................................................................................123 
11.1. 
APPENDIX 1: Study Governance Considerations ...................................................124 
11.1.1. 
Regulatory and Ethical Considerations ....................................................................124 
11.1.2. 
Study Monitoring ......................................................................................................124 
11.1.3. 
Audits and Inspections ..............................................................................................125 
11.1.4. 
Financial Disclosure .................................................................................................126 
11.1.5. 
Recruitment Procedures ............................................................................................126 

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11.1.6. 
Informed Consent Process ........................................................................................126 
11.1.7. 
Protocol Amendments ..............................................................................................127 
11.1.8. 
Protocol Deviations ..................................................................................................128 
11.1.9. 
Data Protection .........................................................................................................128 
11.1.10. 
Sample Retention and Future Biomedical Research ................................................129 
11.1.11. 
Safety Oversight .......................................................................................................129 
11.1.12. 
Dissemination of Clinical Study Data ......................................................................130 
11.1.13. 
Data Quality Assurance and Quality Control ...........................................................130 
11.1.14. 
Data Collection and Management ............................................................................131 
11.1.15. 
Source Documents ....................................................................................................132 
11.1.16. 
Retention of Records ................................................................................................132 
11.1.17. 
Study and Site Closure..............................................................................................133 
11.1.18. 
Publication Policy .....................................................................................................133 
11.2. 
APPENDIX 2: Contraceptive Guidance ...................................................................134 
11.3. 
APPENDIX 3: Adverse Events of Special Interest Terms .......................................136 
11.4. 
APPENDIX 4: CDC Working Case Definition of Pericarditis, Myocarditis, 
and Myopericarditis Occurring After Receipt of COVID-19 mRNA 
Vaccines ....................................................................................................................137 
11.5. 
APPENDIX 5: Protocol Amendment History ..........................................................139 
 
LIST OF TABLES 
Table 1 
Phase 1/2 - Schedule of Events ...................................................................................33 
Table 2 
Phase 2 Northern Hemisphere - Schedule of Events ..................................................36 
Table 3 
Phase 2 Extension - Schedule of Events .....................................................................39 
Table 4 
Phase 1/2 - Study Objectives and Endpoints ..............................................................56 
Table 5 
Phase 2 Northern Hemisphere and Phase 2 Extension - Study Objectives and 
Endpoints ....................................................................................................................58 
Table 6 
Vaccination Groups and Dose Levels .........................................................................61 
Table 7 
Phase 1/2 - Summary of Vaccination Groups.............................................................78 
Table 8 
Phase 2 NH - Summary of Vaccination Groups .........................................................78 
Table 9 
Phase 2 Extension - Summary of Vaccination Groups ...............................................78 
Table 10 
Phase 1/2 Pause Rule Criteria, Events, and Thresholds - Single Event .....................85 

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Table 11 
Phase 1/2 Pause Rule Criteria, Events, and Thresholds – Proportion of 
Participants .................................................................................................................86 
Table 12 
Phase 2 Northern Hemisphere and Phase 2 Extension Pause Rule Criteria, 
Events, and Thresholds - Single Event .......................................................................87 
Table 13 
Solicited Adverse Reactions and Grades ..................................................................100 
Table 14 
Analysis Sets .............................................................................................................114 
Table 15 
Analysis Strategy for Safety Parameters ..................................................................116 
Table 16 
Adverse Events of Special Interest ...........................................................................136 
Table 17 
Case Definitions of Probable and Confirmed Myocarditis, Pericarditis, and 
Myopericarditis .........................................................................................................137 
LIST OF FIGURES 
Figure 1 
Phase 1/2 - Study Schema ...........................................................................................31 
Figure 2 
Phase 2 Northern Hemisphere - Study Schema ..........................................................32 
Figure 3 
Phase 2 Extension - Study Schema .............................................................................32 

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LIST OF ABBREVIATIONS AND DEFINITION OF TERMS 
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 
ALT 
alanine aminotransferase 
AR 
adverse reaction 
AST 
aspartate aminotransferase 
BMI 
body mass index 
BP 
blood pressure 
CD 
cluster of differentiation 
CDC 
United States Centers for Disease Control and Prevention 
CFR 
Code of Federal Regulations 
CI 
confidence interval 
COVID-19 
coronavirus disease 2019 
CRO 
contract research organization 
CSR 
clinical study report 
DSMB 
Data and Safety Monitoring Board 
DSPC 
1,2-distearoyl-sn-glycero-3-phosphocholine 
eCRF 
electronic case report form 
EDC 
electronic data capture 
eDiary 
electronic diary 
EoS 
end of study 
FDA 
Food and Drug Administration 
FIH 
first in human 
FSH 
follicle-stimulating hormone 
GCP 
Good Clinical Practice 
GLSM 
geometric least square mean 
GMFR 
geometric mean fold rise 

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Abbreviation or Specialist Term Definition 
GMT 
geometric mean titer 
GMTr 
geometric mean titer ratio 
HA 
hemagglutinin 
HAI 
hemagglutination inhibition 
HCP 
healthcare practitioner 
HIV 
human immunodeficiency virus 
HRT 
hormone replacement therapy 
IA 
interim analysis 
IB 
investigator’s brochure 
ICF 
informed consent form 
ICH 
International Council for Harmonisation 
IgG 
immunoglobulin G 
ILI 
influenza-like illness 
IM 
intramuscular 
IND 
investigational new drug 
IP 
investigational product 
IRB 
institutional review board 
IRT 
interactive response technology 
IST 
internal safety team 
LLOQ 
lower limit of quantification 
LNP 
lipid nanoparticle 
LTFU 
lost to follow-up 
MAAE 
medically attended adverse event 
MedDRA 
Medical Dictionary for Regulatory Activities 
mRNA 
messenger RNA 
NH 
Northern Hemisphere 
NP 
nasopharyngeal 

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Abbreviation or Specialist Term Definition 
PEG2000-DMG 
1-monomethoxypolyethyleneglycol- 
2,3-dimyristylglycerol with polyethylene glycol of average 
molecular weight 2000 
PP 
per protocol 
QA 
quality assurance 
RT-PCR 
reverse transcription polymerase chain reaction 
SAE 
serious adverse event 
SAP 
statistical analysis plan 
SH 
Southern Hemisphere 
SARS-CoV-2 
severe acute respiratory syndrome coronavirus 2 
SM-102 
heptadecan-9-yl 
8-((2 
hydroxyethyl)(6 
oxo 
6-
(undecyloxy)hexyl)amino)octanoate 
SoE 
schedule of events 
ULOQ 
upper limit of quantification 
US 
United States 
USP 
United States Pharmacopeia 
WBC 
white blood cell 
WHO 
World Health Organization 
 

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2. 
INTRODUCTION 
2.1. 
Study Rationale 
Seasonal influenza viruses are estimated by the World Health Organization (WHO) to cause 3 to 
5 million cases of severe illness and up to 650,000 deaths each year, which is a severe challenge 
to public health (WHO 2018). Influenza epidemics occur each year and follow a seasonal 
circulation pattern with increased cases during the winter months in the Northern Hemisphere 
(NH) and Southern Hemisphere (SH) (Riedel et al 2019). Since influenza viruses continuously 
change through a process termed antigenic drift, the circulating viruses are actively monitored by 
a worldwide monitoring network coordinated by the WHO (Monto 2018). An expert panel 
recommends certain influenza virus strains for vaccine manufacturing, based on observed 
circulation patterns and antigenic changes, twice a year (once for NH and once for SH). 
Influenza A and B viruses are the most relevant influenza viruses for human infection. Therefore, 
current vaccine recommendations include 1 influenza A H1N1 strain, 1 influenza A H3N2 strain, 
and 2 influenza B strains (covering the B/Victoria and B/Yamagata lineages). 
Currently licensed seasonal influenza virus vaccines rarely exceed 60% overall effectiveness and 
are less effective during the years when the circulating viruses do not match the strains selected 
for the vaccine antigens (CDC 2020a). Influenza vaccines based on messenger RNA (mRNA) 
technology could provide several benefits compared with current vaccines, including the ability to 
respond to strain changes more quickly; avoidance of mutations that may be acquired during 
vaccine production in eggs or cell culture; stronger immune responses; and improved protection 
in older adults (Rockman et al 2020). 
2.2. 
Background and Overview 
ModernaTX, Inc. (Sponsor) has developed a rapid response proprietary vaccine platform based on 
the 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. 
Two mRNA vaccines against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 
including Pfizer Inc.’s BNT162b2 (Polack et al 2020) and the Sponsor’s mRNA-1273 
(NCT04283461, NCT04405076, and NCT04470427) have been issued emergency use 
authorizations by the United States (US) Food and Drug Administration (FDA). 
2.2.1. 
mRNA-1010 
The Sponsor is using its mRNA-based platform to develop a novel lipid nanoparticle 
(LNP)-encapsulated mRNA-based vaccine against diseases caused by influenza virus types A 

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and B. The proposed development candidate mRNA-1010 is a quadrivalent vaccine containing 
mRNAs that encode for the hemagglutinins (HAs) of the 4 strains recommended by the WHO for 
cell- or recombinant-based vaccines. Equal amounts of mRNAs that encode for membrane-bound 
wild-type versions of each of the 4 different strains will be used for the HA components. The 
mRNA-1010 development candidate will be administered as a single intramuscular (IM) injection 
and aims to elicit protection from all seasonal influenza viruses covered by the vaccine. 
The Sponsor is conducting this first-in-human (FIH) Phase 1/2 study of mRNA-1010, a seasonal 
influenza vaccine, to establish preliminary safety, reactogenicity, and immunogenicity data to 
support the initiation of a Phase 3 program for this vaccine. The design of this study will include 
an immunogenicity objective for the HA component, using HA inhibition (HAI) as a correlate of 
protection against influenza illness. The rationale for this approach is based on the established 
precedent of using HA-based immunologic correlates for clinical assessment and licensure of 
influenza vaccines (DHHS 2007a; Dunning et al 2016; EMA 2016). In this FIH study, the safety, 
reactogenicity, and immunogenicity of mRNA-1010 vaccine will be compared with placebo 
(Phase 1/2 part) and with an active comparator (Phase 2 NH and Phase 2 Extension parts). The 
vaccine administration in the Phase 1/2 part and the Phase 2 Extension part of the study are planned 
outside the NH influenza season. In the Phase 2 NH part, the vaccine administration is planned 
during the NH influenza season. 
2.2.2. 
Nonclinical Studies 
Using individually formulated HA-encoding mRNAs (preclinical material), 2 mouse 
immunogenicity studies were performed. The HA sequences used for preclinical formulation were 
from wild-type HAs. 
Both studies used a prime/boost regimen with a 3-week interval. Immunized mice were bled on 
Day 21 (3 weeks after the prime dose) and Day 36 (2 weeks after the boost dose), and 
immunoglobulin G (IgG) antibody titers were determined with an enzyme-linked immunosorbent 
assay using recombinant HA proteins. 
The first study compared mice immunized with individual mRNAs or a combination of all 4 HA 
mRNAs at 2 different doses (2 or 0.4 µg of each mRNA), based on the following strains 
recommended for the 2020-2021 NH influenza season: 
• A/Hawaii/70/2019(H1N1)pdm09 
• A/Hong Kong/45/2019(H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 

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High IgG antibody titers were observed against all HAs following immunization, with both 
individual mRNA constructs and mRNA combinations after a single dose. A dose response and 
booster effect were observed for most mRNA constructs (individual and combinations). 
The second mouse immunogenicity study aimed to confirm that the 2021 SH composition is 
similarly immunogenic with the 2020-2021 NH composition. The compositions differed only for 
the H1N1 strain; the SH composition included A/Wisconsin/588/2019(H1N1)pdm09 instead of 
the A/Hawaii/70/2019(H1N1)pdm09 strain. 
No difference in immunogenicity (HA IgG antibody titers) based on the strain/mRNA construct 
used for immunization (A/Hawaii/70/2019 in the NH composition versus A/Wisconsin/588/2019 
in the SH composition) was observed, suggesting that the mRNA platform will support annual 
strain updates. 
Additional studies to assess protection of mice from challenge with mouse-adapted H1N1 and 
H3N2 viruses after a single immunization and a study to assess immunogenicity and protection 
from H1N1 challenge after 2 immunizations in ferrets are currently ongoing. Results will be 
available in the planned investigational new drug (IND) application. 
A detailed review of the nonclinical experience with mRNA-1010 vaccine will be provided in the 
investigator’s brochure (IB). 
2.2.3. 
Clinical Studies 
No clinical studies with mRNA-1010 have been performed to date. 
2.3. 
Benefit/Risk Assessment 
2.3.1. 
Known Potential Benefits 
The following benefits may accrue to participants who receive the mRNA-1010 vaccine: 
• The mRNA-1010 vaccine may be effective against seasonal influenza strains as 
defined by the WHO for the 2020-2021 SH flu season (Phase 1/2) or against the 
seasonal influenza strains as defined by the WHO for the 2021-2022 NH flu season 
(Phase 2 NH and Phase 2 Extension). 
• Participants will have a baseline (Day 1) evaluation for respiratory pathogens 
(Phase 1/2 part), including influenza virus and SARS-CoV-2, and ongoing 
surveillance for influenza-like illness (ILI) and/or coronavirus disease 2019 
(COVID-19) throughout the study (Phase 1/2, Phase 2 NH, and Phase 2 Extension). 
• The study will contribute to the development of a potentially efficacious vaccine 
against seasonal influenza. 

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2.3.2. 
Risks From Study Participation and Their Mitigation 
Adverse events (AEs) ranging from immediate mild allergic reactions (eg, urticaria) to systemic 
allergic reactions (eg, anaphylaxis) may occur following any vaccination. Systemic allergic 
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). Since the authorization of 
the mRNA-1273 vaccine for COVID-19, the US Centers for Disease Control and Prevention 
(CDC) estimate of the rate of anaphylaxis based on reporting in the Vaccine Adverse Event 
Reporting 
System 
is 
approximately 
2.5 
cases/million 
doses 
administered 
(Shimabukuro et al 2021). As a precaution, all participants will remain under observation at the 
study site for at least 60 minutes after injection. 
Vasovagal syncope (fainting) can occur before or after any vaccination, is usually triggered by 
pain or anxiety associated with the injection and is not related to the substance injected. Therefore, 
it is important that standard precautions and procedures are followed to avoid injury from fainting. 
Intramuscular injection with other mRNA vaccines manufactured by the Sponsor containing the 
proprietary 
SM-102 
(heptadecan-9-yl 
8-((2-hydroxyethyl)(6-oxo-6-
(undecyloxy)hexyl)amino)octanoate) lipid formulation have commonly resulted in transient and 
self-limiting local inflammatory reactions. These typically included pain, erythema (redness), or 
swelling (hardness) at the injection site, which were mostly mild to moderate in severity and 
usually occurred within 24 hours of injection. Laboratory abnormalities (including increases in 
liver function tests and serum lipase levels) following injection have been observed in early phase 
clinical studies with similar mRNA-based vaccines. These abnormalities were without clinical 
symptoms or signs and returned toward baseline (Day 1) values over time. 
In a recently completed Phase 3 study of mRNA-1273 vaccine for COVID-19 in 30,420 healthy 
adults, the most commonly reported local reactions included pain, swelling, and erythema at the 
injection site. Most of these reactions were Grade 1 or 2 in severity and resolved within 3 to 4 days 
of onset. The most commonly reported systemic reactions were headache, myalgia, arthralgia, 
fatigue, chills, and fever. In most cases, the reactions resolved spontaneously within several days 
(Baden et al 2021). 
Similarly, safety results from Phase 1 studies conducted by the Sponsor on 2 mRNA vaccines 
containing the HA glycoproteins from the H10N8 and H7N9 avian influenza viruses were well 
tolerated, although the Sponsor’s LNP/mRNA platform has since been updated (eg, SM-102 is 
used in mRNA-1010 and mRNA-1273; Feldman et al 2019). 
There have been very rare reports of myocarditis and pericarditis occurring after vaccination with 
COVID-19 mRNA vaccines. 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 

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within a short time following standard treatment and rest. Investigators and study participants 
should be alert to the signs and symptoms of myocarditis and pericarditis (Gargano et al 2021). 
2.3.3. 
Overall Benefit/Risk Conclusion 
Three dose levels (50, 100, and 200 µg of total mRNA) of mRNA-1010 vaccine administered as a 
single IM injection will be evaluated in the Phase 1/2 part of the study. The safety, reactogenicity, 
and immunogenicity of the 3 dose levels of mRNA-1010 will be compared with placebo. The study 
schema for the Phase 1/2 part of the study is provided in Figure 1. 
In the Phase 1/2 part of the study, each vaccination group will have 2 stages: initial stage and 
expansion stage. A total of 36 participants (9 participants in each vaccination group) will be 
randomly assigned in the initial stage in parallel fashion. Enrollment and vaccination in the 
expansion stage will begin only after an internal safety team (IST) performs a blinded review of 
all available safety data up to 7 days after vaccination from the 36 participants in the initial stage 
and determines that no pause rules have been met. As an additional safeguard, the vaccine 
administration in the Phase 1/2 part of this FIH study is planned outside the NH influenza season. 
In the Phase 2 NH part, the three dose levels of mRNA-1010 vaccine to be evaluated are 25, 50, 
and 100 µg of total mRNA based on interim analysis (IA) of the Phase 1/2 part. In addition, the 
Phase 2 NH part of the study will also include a composition change of mRNA-1010 (strain update 
for the 2021-2022 NH season), as well as the inclusion of a licensed active comparator. In this 
part, vaccine administration is planned during the NH influenza season. The study schema for the 
Phase 2 NH part of the study is provided in Figure 2. 
In the Phase 2 Extension part, the 3 dose levels of mRNA-1010 vaccine to be evaluated are 6.25, 
12.5, and 25 µg of total mRNA based on IA of the Phase 1/2 part. The Phase 2 Extension part of 
the study will include the same composition of mRNA-1010 as the Phase 2 NH part. In this part, 
vaccine administration is planned outside the NH influenza season. The study schema for the 
Phase 2 Extension part of the study is provided in Figure 3. 
Serological data from all participants will be used to infer vaccine immunogenicity. All 
participants will be followed up for 6 months after the study vaccination. Safety will be monitored 
throughout the study (Section 8.4). 
Considering the nonclinical data for the mRNA-1010 vaccine and the safety data for the other 
mRNA vaccines manufactured by the Sponsor to date that contain the proprietary SM-102 lipid 
formulation, the Sponsor considers the potential benefits of participation to exceed the risks. 

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3. 
OBJECTIVES AND ENDPOINTS 
3.1. 
Phase 1/2 
The objectives of the Phase 1/2 part of the study and the endpoints associated with each objective 
are provided in Table 4. 
Table 4 
Phase 1/2 - Study Objectives and Endpoints 
Objectives 
Endpoints 
Primary 
 
• 
To evaluate the safety and reactogenicity of 3 
dose levels (50, 100, and 200 µg) of mRNA-
1010 vaccine administered as a single dose 
• 
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, AESIs, and MAAEs 
from Day 1 through Day 181/EoS 
• 
Safety laboratory abnormalities through 7 days 
after vaccination 
• 
To evaluate the humoral immunogenicity of 3 
dose levels (50, 100, and 200 µg) of mRNA-
1010 vaccine administered as a single dose 
against vaccine-matched influenza A and B 
strains at Day 29 
• 
GMT and GMFR at Day 29 compared with 
Day 1 (baseline) and percentage of participants 
with seroconversion, defined as a Day 29 titer 
≥ 1:40 if baseline is < 1:10 or a 4-fold or 
greater rise if baseline is ≥ 1:10 in anti-HA 
antibodies measured by HAI assay  
Secondary 
 
• 
To evaluate the humoral immunogenicity of 3 
dose levels (50, 100, and 200 µg) of mRNA-
1010 vaccine administered as a single dose 
against vaccine-matched influenza A and B 
strains 
at 
all 
evaluable 
humoral 
immunogenicity time points 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI or MN assays at all 
evaluable humoral immunogenicity time 
points compared with Day 1 (baseline) 

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Objectives 
Endpoints 
Exploratory (May be Performed) 
 
• 
To evaluate the humoral immunogenicity of 3 
dose levels (50, 100, and 200 µg) of mRNA-
1010 vaccine administered as a single dose 
against 
vaccine-mismatched 
or 
drifted 
influenza A and B strains 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI or MN assays against 
vaccine-mismatched 
or 
drifted 
strains 
compared with Day 1 (baseline) 
• 
To evaluate the cellular immunogenicity of 
3 dose levels (50, 100, and 200 µg) of mRNA-
1010 vaccine administered as a single dose in 
a subset of participants 
• 
Frequency, magnitude, and phenotype of 
virus-specific T-cell and B-cell responses 
measured by flow cytometry or other methods 
as well as targeted repertoire analysis of 
B cells and T cells after vaccination 
• 
To further characterize antibody responses, for 
example, Fc-mediated function, avidity, or 
epitope specificity, of 3 dose levels (50, 100, 
and 200 µg) of mRNA-1010 vaccine 
administered as a single dose 
• 
Frequency, specificities, or other endpoints to 
be determined for further characterization of 
antibody responses 
• 
To assess the occurrence of ILI in study 
participants and characterize their immune 
response to infection and viral isolates 
• 
Frequency of RT-PCR-confirmed ILI and 
assessment 
of 
immune 
responses 
in 
participants with RT-PCR-confirmed ILI 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; EoS = end of study; 
Fc = fragment crystallizable; GMFR = geometric mean fold rise; GMT = geometric mean titer; HA = hemagglutinin; 
HAI = hemagglutination inhibition; ILI = influenza-like illness; MAAE = medically attended adverse event; 
MN = microneutralization; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event. 
3.2. 
Phase 2 Northern Hemisphere and Phase 2 Extension 
The objectives of the Phase 2 NH and Phase 2 Extension parts of the study and the endpoints 
associated with each objective are provided in Table 5. 

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Table 5 
Phase 2 Northern Hemisphere and Phase 2 Extension - Study Objectives and 
Endpoints 
Objectives 
Endpoints 
Primary 
 
• 
To evaluate the humoral immunogenicity of 
mRNA-1010 vaccine relative to that of an 
active comparator against vaccine-matched 
influenza A and B strains at Day 29 
• 
GMT at Day 29 as measured by HAI 
• 
Proportion 
of 
participants 
reaching 
seroconversion at Day 29 as measured by HAI 
• 
To evaluate the safety and reactogenicity of 
mRNA-1010 vaccine 
• 
Frequency and grade of each solicited local 
and systemic reactogenicity ARs 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, AESIs, and MAAEs 
from Day 1 through Day 181/EoS 
Secondary 
 
• 
To evaluate the humoral immunogenicity of 
each vaccine group against vaccine-matched 
influenza A and B strains at Day 29 
• 
The frequency of participants with HAI 
seroconversion 
and 
the 
frequency 
of 
participants with an HAI titer ≥ 1:40 at Day 29 
• 
GMFR comparing Day 29 to Day 1 (baseline) 
as measured by HAI 

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Objectives 
Endpoints 
Exploratory (May be Performed) 
 
• 
To evaluate the relative vaccine efficacy of 
mRNA-1010 vaccine to an active comparator 
in preventing RT-PCR-confirmed ILI caused 
by any strain of influenza using different case 
definitions 
• 
RT-PCR-confirmed protocol- or CDC-defined 
ILI that begin at least 14 days after vaccination 
through Day 181/EoS caused by any strain of 
influenza regardless of antigenic match to the 
strains selected for the seasonal vaccine 
• 
To evaluate the humoral immunogenicity of 
mRNA-1010 vaccine to that of an active 
comparator 
against 
vaccine-matched 
or 
vaccine-mismatched influenza A and B strains, 
including the use of alternative methods 
• 
GMT and GMFR of anti-HA antibodies as 
measured by assays such as MN assays or 
alternative methods against vaccine-matched 
or vaccine-mismatched strains on Day 29 
compared with Day 1 (baseline) 
• 
GMT and GMFR of anti-HA antibodies as 
measured by HAI against vaccine-mismatched 
strains at Day 29 compared with Day 1 
(baseline) 
• 
To evaluate the humoral immunogenicity at 
Days 91 and 181/EoS in a subset of 
participants 
• 
GMT, GMFR, and frequency of participants 
with HAI titers ≥ 1:40 at Days 91 and 181/EoS 
• 
To further characterize the immune response to 
mRNA-1010 vaccine and active comparator 
• 
Frequency, specificities, or other endpoints to 
be determined for further characterization of 
immune responses 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; CDC = Centers for Disease 
Control and Prevention; EoS = end of study; GMFR = geometric mean fold rise; GMT = geometric mean titer; 
HA = hemagglutinin; HAI = hemagglutination inhibition; ILI = influenza-like illness; MAAE = medically attended adverse 
event; MN = microneutralization; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event. 
 

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4. 
STUDY DESIGN 
4.1. 
General Design 
This FIH study is a Phase 1/2, randomized, observer-blind, dose-ranging study to evaluate the 
safety, reactogenicity, and immunogenicity of mRNA-1010 vaccine in adult participants 
≥ 18 years of age. The study comprises 3 parts: Phase 1/2, Phase 2 NH, and Phase 2 Extension. 
The Phase 1/2 part of the study will be a randomized, observer-blind, dose-ranging, 
placebo-controlled study to evaluate the safety, reactogenicity, and immunogenicity of 
mRNA-1010 vaccine in healthy adult participants ≥ 18 years of age. The Phase 2 NH and Phase 2 
Extension parts of the study will be randomized, observer-blind, dose-ranging, active-controlled 
studies to evaluate the immunogenicity, reactogenicity, and safety of mRNA-1010 vaccine in 
medically stable adults 18 years and older. 
All participants in each part of the study will participate in a screening period (up to 28 days before 
Day 1), treatment period (single dose of vaccine on Day 1), and a follow-up period (up to 6 months 
after vaccination). 
In the Phase 1/2 part of the study, the mRNA-1010 vaccine to be tested includes mRNAs that 
encode for the surface glycoprotein HAs of the following influenza virus strains recommended by 
the WHO for 2020-2021 SH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Hong Kong/45/2019(H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
In the Phase 2 NH and Phase 2 Extension parts of the study, the mRNA-1010 vaccine to be tested, 
includes mRNAs that encode for the surface glycoprotein HAs of the following influenza virus 
strains recommended by the WHO for 2021-2022 NH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Cambodia/e0826360/2020 (H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
Different dose levels of mRNA-1010 vaccine will be evaluated. Placebo will be included in the 
Phase 1/2 part and an active comparator (licensed quadrivalent seasonal influenza vaccine) will be 
included in the Phase 2 NH and Phase 2 Extension parts.  

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In the Phase 1/2 part, each vaccination group will have 2 stages: initial stage and expansion stage. 
The schema for the Phase 1/2, Phase 2 NH, and Phase 2 Extension parts of the study are presented 
in Figure 1, Figure 2, and Figure 3, respectively. Table 6 (Parts A, B, and C) lists the vaccination 
groups and dose levels that will be evaluated in each part of the study; Part D lists the total number 
of study participants in each study part and overall. 
Table 6 
Vaccination Groups and Dose Levels 
A) Phase 1/2 
 
Number of Participants 
Vaccination 
Group 
Investigational 
Product 
mRNA 
or HA (µg) 
Total  
Dose (µg) 
Phase 1/2 
Initial 
Stage 
Expansion 
Stage 
Total 
1 
mRNA-1010 
12.5 
50 
9 
36 
45 
2 
mRNA-1010 
25 
100 
9 
36 
45 
3 
mRNA-1010 
50 
200 
9 
36 
45 
4 
Placebo 
– 
– 
9 
36 
45 
Total 
36 
144 
180 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA. 
B) Phase 2 NH 
 
Number of Participants 
Vaccination 
Group 
Investigational Product 
mRNA  
or HA (µg) 
Total  
Dose (µg) 
Phase 2 NH 
1 
mRNA-1010 
6.25 
25 
150 
2 
mRNA-1010 
12.5 
50 
150 
3 
mRNA-1010 
25 
100 
150 
 4 
Active comparator  
15 
60 
50 
Total 
500 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA; NH = Northern Hemisphere. 
 

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C) Phase 2 Extension 
 
Number of Participants 
Vaccination 
Group 
Investigational Product 
Total  
Dose (µg) 
Phase 2 Extension 
1 
mRNA-1010 
6.25 
50 
2 
mRNA-1010 
12.5 
50 
3 
mRNA-1010 
25 
50 
4 
Active comparator  
60 
50 
Total 
200 
Abbreviations: HA = hemagglutinin; mRNA = messenger RNA. 
Note: Mass percent in mRNA-1010 is 25% for each of the 4 HAs. 
D) Total Number of Participants 
Study Part 
Number of Participants 
Phase 1/2 
180 
Phase 2 NH 
500 
Phase 2 Extension 
200 
Total 
880 
Abbreviations: NH = Northern Hemisphere. 
Healthy (Phase 1/2) and medically stable (Phase 2 NH and Phase 2 Extension) adults ≥ 18 years 
of age will be screened and enrolled. For the Phase 2 NH and Phase 2 Extension parts, participants 
with chronic diseases requiring ongoing medical intervention within the last 3 months prior to 
enrollment as well as those with immunocompromising conditions or medications will be 
excluded. The complete lists of inclusion and exclusion criteria for the Phase 1/2, Phase 2 NH, and 
Phase 2 Extension parts of the study are provided in Section 5.1 (Phase 1/2) and Section 5.2 
(Phase 2 NH and Phase 2 Extension). 
In the Phase 1/2 part, approximately 180 participants will be randomly assigned in a 1:1:1:1 ratio 
to receive mRNA-1010 50 μg, mRNA-1010 100 μg, mRNA-1010 200 μg, or placebo, with 
approximately 45 participants randomly assigned to each vaccination group. A total of 
36 participants (9 participants in each vaccination group) will be randomly assigned in the initial 
stage of the study. The IST will perform a blinded review of all safety data up to 7 days after 
vaccination from the 36 participants in the initial stage. After the IST confirms that no pause rules 
(Section 7.1) have been met in the 36 participants in the initial stage, enrollment will begin in the 
expansion stage. A total of 144 participants (36 participants in each vaccination group) will be 
randomly assigned in the expansion stage of the study. Randomization in the expansion stage will 
be stratified by age (18 to < 50 years versus ≥ 50 years) and will be balanced across the 2 age 
groups within each vaccination group. 

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The Phase 2 NH part of the study will enroll and randomize approximately 500 participants in a 
3:3:3:1 ratio to 1 of 4 vaccination groups to receive a single dose of mRNA-1010 at different dose 
levels (25, 50, or 100 µg total mRNA) or a single dose of a licensed quadrivalent seasonal influenza 
vaccine (active comparator). Randomization to individual vaccination groups will proceed with 
parallel randomization among the 3 dose levels of mRNA-1010 (25, 50, and 100 µg total mRNA; 
Vaccination Groups 1 to 3) and the active comparator (Vaccination Group 4). Randomization will 
be stratified by age categories (18 to < 50 years, 50 to < 65 years, or ≥ 65 years) and vaccination 
status in the previous flu season (received or not received). 
The Phase 2 Extension part of the study will enroll and randomize approximately 200 participants 
in a 1:1:1:1 ratio to 1 of 4 vaccination groups to receive a single dose of mRNA-1010 at different 
dose levels (6.25, 12.5, or 25 µg total mRNA) or a single dose of a licensed quadrivalent seasonal 
influenza vaccine (active comparator). Randomization to individual vaccination groups will 
proceed with parallel randomization among the 3 dose levels of mRNA-1010 (6.25, 12.5, or 25 µg 
total mRNA; Vaccination Groups 1 to 3) and the active comparator (Vaccination Group 4). 
Randomization will be stratified by age categories (18 to < 50 years, or ≥ 50 years).  
Table 1, Table 2, and Table 3 display the Schedule of Events (SoE) for the Phase 1/2, Phase 2 NH, 
and Phase 2 Extension parts of the study, respectively. The Phase 1/2 part of the study comprises 
6 scheduled study site visits: Screening, Day 1, Day 8, Day 29 (Month 1), Day 57 (Month 2), and 
Day 181 (Month 6). The Phase 2 NH and Phase 2 Extension parts of the study comprise 
5 scheduled study site visits: Screening, Day 1, Day 29 (Month 1), Day 91 (Month 3), and Day 181 
(Month 6). The Phase 2 Extension part also contains an optional study site visit on Day 4 for blood 
sample collection. There are also scheduled safety phone calls to collect medically attended AEs 
(MAAEs), AEs leading to withdrawal from study participation, serious AEs (SAEs), AEs of 
special interest (AESIs), information about concomitant medications associated with these events, 
and to collect information about receipt of nonstudy vaccinations temporally associated with these 
events. These phone calls are scheduled monthly from Day 91 through Day 151 during the 
Phase 1/2 part and on Days 8 and 15 during the Phase 2 NH and Phase 2 Extension parts of the 
study. 
The study duration will be approximately 7 months for each participant enrolled in each part of 
the study: a screening period of up to 1 month and a study period of 6 months that includes a single 
dose of vaccine on Day 1. The participant’s final visit will be on Day 181 (Month 6), six months 
after the study vaccination. 
All participants in each part of the study will be followed for safety and reactogenicity. On Day 1, 
participants will be instructed how to document, and report solicited adverse reactions (ARs) and 
ILI symptoms (for Phase 2 NH part only) with a provided electronic diary (eDiary) (Section 8.1.1). 
Solicited ARs will be assessed for 7 days (the day of injection and the following 6 days) after the 

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study vaccination, and unsolicited AEs will be assessed for 28 days after the study vaccination; 
SAEs, AESIs, and MAAEs will be assessed from Day 1 throughout the study. 
All participants in the Phase 1/2 part of the study will provide nasopharyngeal (NP) swab samples 
before the injection on Day 1 for assessment of asymptomatic infection with respiratory pathogens, 
including influenza virus and SARS-CoV-2. A study site visit or a consultation (unscheduled study 
visit) will be arranged within 24 hours or as soon as possible to collect an NP swab sample if 
participants experience symptoms consistent with the CDC definition of ILI (Section 8.4.6) and/or 
COVID-19 during the course of the study.  
For the Phase 2 NH part, as part of the safety assessments, active and passive surveillance for ILI 
will be conducted between Day 1 through Day 181/end of study (EoS). For active surveillance, 
participants will be instructed to report whether ILI symptoms have been experienced, 3 to 4 times 
weekly from Day 1 through Day 29 and twice weekly from Day 30 through Day 181/EoS, via 
eDiary or telephone calls. If symptoms occur, participants will be directed to return to the study 
site as soon as possible, but no later than 72 hours after the onset of symptoms, for medical 
evaluation and an NP swab. Participants will be contacted by the study site if they have missed 
reporting in the eDiary. If there is no response to an eDiary prompt for 2 consecutive entries, the 
study site staff will contact the participant by telephone. For passive surveillance, participants will 
be instructed to report symptoms of ILI any time from Day 1 through Day 181/EoS. Participants 
in the Phase 2 NH part who manifest protocol-defined ILI (Section 8.4.6) between Day 1 through 
Day 29 will be evaluated by real-time reverse transcription polymerase chain reaction (RT-PCR) 
testing of an NP specimen for influenza (and other respiratory pathogens). An NP swab specimen 
for pathogens, including influenza virus and SARS-CoV-2 will be collected any time from Day 1 
through Day 181/EoS if participants have protocol-defined ILI or symptoms suggestive of 
COVID-19 or other upper or lower respiratory infection at the Investigator’s discretion. 
For the Phase 2 Extension part, a study site visit or a consultation (unscheduled study visit) will 
be arranged within 72 hours after the onset of symptoms to collect an NP swab sample if 
participants experience symptoms consistent with the US CDC definition of ILI and/or COVID-19 
during the course of the study. 
All participants in the Phase 1/2 part of the study will provide a blood specimen before injection 
on Day 1 and additional blood specimens through the next 6 months for immunogenicity (on 
Days 8, 29, and 181/EoS). In the Phase 2 NH and Phase 2 Extension parts, all participants will 
provide a blood specimen for immunogenicity assessments before injection on Day 1 and then on 
Day 29. In addition, blood samples from a subset of participants at Days 91 and 181/EoS may be 
used for additional assessments. The Phase 2 Extension part also contains an optional study site 
visit on Day 4 for blood sample collection for potential biomarker analysis. Furthermore, blood 

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samples for safety or other medical concerns may be collected according to the Investigator’s 
judgment at scheduled study site visits during each part of the study. 
Participants may experience AEs that necessitate an unscheduled visit. There may also be 
situations in which the Investigator asks a participant to report for an unscheduled visit following 
the report of an AE. Additional examinations may be conducted at these visits as necessary to 
ensure the safety and well-being of participants during the study. Electronic case report forms 
(eCRFs) should be completed for each unscheduled visit. 
The study will be observer-blind as to which investigational product (IP; mRNA-1010 or placebo 
in the Phase 1/2 part; mRNA-1010 or the active comparator in the Phase 2 NH and Phase 2 
Extension parts) or dose level is administered. Participants will receive the IP by 0.5-mL IM 
injection on Day 1. All participants, study site staff involved in participant assessment, and 
Sponsor personnel (or its designees) will be blinded to individual dosing assignment until the study 
database is locked and unblinded. Details regarding blinding are provided in Section 9.1 and the 
study Data Blinding Plan. 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. 
Safety monitoring for this study will include blinded study team members, inclusive of, at a 
minimum, the Sponsor’s medical monitor, medical monitor of the contract research organization 
(CRO), a blinded IST, and an unblinded Data and Safety Monitoring Board (DSMB). The study 
team will conduct ongoing blinded safety reviews during the study and will be responsible for 
notifying the IST and DSMB of potential safety signal events or the triggering of pause rules 
(Section 7.1). 
For the initial stage in the Phase 1/2 part of the study, the IST will conduct a blinded review of all 
available safety data after at least 36 participants (9 participants per vaccination group) have 
completed their Day 8 Visit. Vaccination of the remaining participants in the expansion stage will 
continue in each vaccination group if no pause rules have been met and the safety and tolerability 
are acceptable. Prior to the start of the Phase 2 NH part of the study, the IST will also conduct a 
blinded review of available safety data from the Phase 1/2 part. Finally, the IST will also conduct 
ad hoc reviews as requested by the study medical monitor and the study team. An independent 
unblinded DSMB will be used throughout the conduct of this study. This committee will be 
composed of independent members with relevant therapeutic and/or biostatistical expertise to 
allow for the ongoing unblinded review of safety data from this study population. Safety data will 
be reviewed according to intervals defined in the DSMB charter and will also occur as needed 
when study stopping or pausing criteria are met, or as otherwise requested by the study team and/or 
IST. See Section 11.1.11 for details on the IST and DSMB constituted in this study. 

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For the Phase 1/2 part, there is 1 planned IA, which will include safety and immunogenicity data 
of all participants (all vaccination groups) after completion of the Day 29 Visit. For the Phase 2 
NH and Phase 2 Extension parts, an IA of safety (reactogenicity and immunogenicity as 
applicable) will be performed after participants have completed the Day 29 Visit for each part of 
the study. See Section 9.6 for details. 
Immunizations for the Phase 1/2 part of the study are planned during the NH summer and all 
participants will be recommended to receive a licensed 2021-2022 NH seasonal influenza vaccine 
during their participation in the study after completion of the Day 29 Visit. Immunizations for the 
Phase 2 NH part of the study are planned during the NH influenza season. Immunizations for the 
Phase 2 Extension part are planned during the NH spring. 
4.2. 
Scientific Rationale for Study Design 
This study is designed as an observer-blind study. In the Phase 1/2 part of the study, participants 
in Vaccination Groups 1 to 3 will receive mRNA-1010 vaccine and those in Vaccination Group 4 
will receive placebo. The placebo will be used for descriptive comparisons of safety and 
immunogenicity. In the Phase 2 NH part, participants in Vaccination Groups 1 to 3 will receive 
mRNA-1010 vaccine and those in Vaccination Group 4 will receive a licensed quadrivalent 
seasonal influenza vaccine in order to assess noninferior immunogenicity. In the Phase 2 Extension 
part, participants in Vaccination Groups 1 to 3 will receive mRNA-1010 vaccine and those in 
Vaccination Group 4 will receive a licensed quadrivalent seasonal influenza vaccine in order to 
compare immunogenicity. 
In this observer-blind study, all participants, study site staff involved in participant assessment, 
and Sponsor personnel (or its designees) will be blinded to participant vaccine allocation. A limited 
number of Sponsor and/or CRO personnel will be unblinded to conduct safety data analyses for 
the DSMB safety data reviews (as described in the DSMB charter) and perform the IA. Unblinded 
study personnel, who will not participate in any other aspect of the study, will perform IP 
accountability, dose preparation, and IP administration. 
In the Phase 1/2 part, all participants will provide NP swab samples before the injection on Day 1 
for assessment of asymptomatic infection with respiratory pathogens, including influenza virus 
and SARS-CoV-2, as influenza or COVID-19 symptoms may confound reactogenicity 
assessments. Furthermore, if a participant experiences an MAAE or any signs or symptoms 
suggesting ILI and/or COVID-19, an additional NP swab sample will be collected to confirm the 
diagnosis via RT-PCR. In the Phase 2 NH and Phase 2 Extension parts, the NP swab samples for 
assessment of infection with respiratory pathogens, including influenza virus and SARS-CoV-2, 
will be collected anytime from Day 1 through Day 181/EoS if the participants have 
protocol-defined ILI (Phase 2 NH) or CDC-defined ILI (Phase 2 Extension) or symptoms 

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suggestive of COVID-19 or other upper or lower respiratory infection at the Investigator’s 
discretion. Participants who manifest ILI between Day 1 through Day 29 will be evaluated by 
RT-PCR testing of an NP specimen for influenza (and other respiratory pathogens). Additionally, 
in all parts of the study, clinical information may be collected to evaluate the severity of the clinical 
case. 
4.3. 
Choice of Vaccine Dose 
No clinical studies of mRNA-1010 have been completed to date. 
Previous studies of the Sponsor’s mRNA/LNP SM-102 platform have assessed dose levels as high 
as 250 µg for mRNA-1273, a SARS-CoV-2 vaccine (Jackson et al 2020, NCT04283461), and 
mRNA-1893, a Zika vaccine (unpublished data, NCT04064905). Additionally, doses up to 300 µg 
of the multivalent mRNA-1647, a cytomegalovirus vaccine (unpublished data, NCT03382405), 
and the multivalent mRNA-1653, a combination vaccine against human metapneumovirus and 
parainfluenza virus type 3 (unpublished data, NCT03392389), have been tested in Phase 1 studies. 
The vaccines were generally well tolerated at these dose levels. 
The Sponsor has previously evaluated the immunogenicity of 2 mRNA vaccines containing the 
HA glycoprotein from the H10N8 and H7N9 influenza viruses. Although differences in the 
mRNA/LNP platform and the administration schedule (2 doses were given 3 weeks apart) limit 
extrapolation of the safety data, these mRNA vaccines against H10N8 and H7N9 influenza viruses 
elicited robust humoral immune responses and were well tolerated up to dose levels of 100 µg (for 
each HA type; Feldman et al 2019). 
The FIH Phase 1/2 clinical study of mRNA-1010 vaccine will evaluate the immunogenicity of 
mRNA-1010 at proposed total dose levels of 50 µg (12.5 µg/mRNA), 100 µg (25 µg/mRNA), and 
200 µg (50 µg/mRNA), administered as a single IM injection in healthy adults ≥ 18 years of age. 
Based on IA results of the Phase 1/2 study, the 200 µg dose of mRNA-1010 did not meet the 
Sponsor's desired reactogenicity profile. In the Phase 2 NH part of the study, the Sponsor intends 
to test a lower dose level of 25 µg in lieu of 200 µg, keeping the previous dose levels of 50 and 
100 µg unchanged. Thus, the Phase 2 NH part will evaluate the immunogenicity of mRNA-1010 
at proposed total dose levels of 25 µg (6.25 µg/mRNA), 50 µg (12.5 µg/mRNA), and 100 µg 
(25 µg/mRNA), administered as a single IM injection in medically stable adults ≥ 18 years of age. 
Based on IA of the Phase 1/2 study, vaccination with mRNA-1010 elicited HAI antibodies at all 
dose levels tested. In the Phase 2 Extension part of the study, the Sponsor intends to test lower 
dose levels of 6.25 and 12.5 µg of mRNA-1010, and to keep the Phase 2 NH mRNA-1010 dose 
level of 25 µg and the active comparator unchanged. Thus, the Phase 2 Extension part will evaluate 
the immunogenicity of mRNA-1010 at proposed total dose levels of 6.25, 12.5, and 25 µg, 
administered as a single IM injection in medically stable adults ≥ 18 years of age. 

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4.4. 
End of Study Definition 
For each part of the study, participants are considered to have completed the study if they complete 
the final visit on Day 181 (Month 6), six months after the study vaccination on Day 1. 
The study will be considered ended at the completion of the last visit of the last participant in the 
Phase 2 Extension part of the study or the last scheduled procedure as shown in the SoE (Table 3) 
for the last participant in the Phase 2 Extension part of the study. 

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5. 
STUDY POPULATION 
Prospective approval of protocol deviations to recruitment and enrollment criteria, also known as 
protocol waivers or exemptions, is not permitted. 
5.1. 
Phase 1/2 
5.1.1. 
Inclusion Criteria 
Each participant must meet all of the following criteria at the Screening Visit and at Day 1, unless 
noted otherwise, to be enrolled in this study: 
1. Is an adult, ≥ 18 years of age at the time of consent (Screening Visit), who is in good 
health, in the opinion of the Investigator, based on review of medical history and physical 
examination performed at screening. 
2. Understands and is willing and physically able to comply with protocol-mandated 
follow-up, including all procedures, in the opinion of the Investigator. 
3. Has provided written informed consent for participation in this study, including all 
evaluations and procedures as specified in this protocol. 
4. Has a body mass index (BMI) of 18 kg/m2 to 35 kg/m2 (inclusive) at the Screening Visit. 
5. If female and is not of childbearing potential, may be enrolled in the study. The definition 
of a female of childbearing potential is provided in Appendix 2 (Section 11.2). A 
follicle-stimulating hormone (FSH) level may be measured at the discretion of the 
Investigator to confirm postmenopausal status. 
6. If female and of childbearing potential, meets all of the following criteria to be enrolled 
in the study: 
• Has a negative pregnancy test at the Screening Visit and on the day of vaccination 
(Day 1). 
• Has practiced adequate contraception (Section 11.2) or has abstained from all 
activities that could result in pregnancy for at least 28 days prior to Day 1. Adequate 
female contraception is defined as consistent and correct use of an FDA-approved 
contraceptive method in accordance with the product label. 
• Has agreed to continue adequate contraception through 3 months following vaccine 
administration. 
• Is not currently breastfeeding. 
 

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5.1.2. 
Exclusion Criteria 
Participant meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had significant exposure to someone with laboratory-confirmed SARS-CoV-2 
infection, COVID-19, or ILI in the past 14 days prior to the Screening Visit, as defined 
by the CDC as close contact with someone who has COVID-19 (CDC 2021a). 
2. Has a positive SARS-CoV-2 RT-PCR or antigen test in the past 10 days prior to the 
Screening Visit. 
a. A participant who has a positive SARS-CoV-2 serological test in the past 10 days 
prior to the Screening Visit but is otherwise asymptomatic and does not have a 
positive SARS-CoV-2 RT-PCR or antigen test at the Screening Visit may still be 
enrolled if they meet the study eligibility criteria. 
b. A participant who has a positive SARS-CoV-2 RT-PCR or antigen test in the past 
10 days prior to the Screening Visit may be enrolled 10 days after symptom onset or 
10 days after the date of the first positive SARS-CoV-2 RT-PCR test without repeat 
testing, provided the participant is asymptomatic and meets the study eligibility 
criteria as well as the CDC recommendation for duration of isolation and precautions 
(CDC 2021b). 
c. Additionally, a participant who meets all study eligibility criteria (note exclusion 
criterion No. 4) at the Screening Visit but later tests positive for SARS-CoV-2 at 
Visit 1 will continue participation in the study. 
3. Has clinical screening laboratory values (white blood cell [WBC] count, hemoglobin, 
platelets, alanine aminotransferase [ALT], aspartate aminotransferase [AST], creatinine, 
alkaline phosphatase, and total bilirubin) > Grade 1. 
4. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 
the 28-day screening window and will retain their initially assigned participant number. 
5. Has a pre-existing medical condition that is not stable, at the discretion of the 
Investigator. A stable medical condition is defined as disease not requiring significant 
change in therapy or hospitalization for worsening disease during the 2 months before 
enrollment. Participants may be rescreened if they are not medically stable at the 
Screening Visit. Medical conditions include (but are not limited to) the following: 
a. Uncontrolled hypertension or systolic blood pressure (BP) > 150 mm Hg or diastolic 
BP > 90 mm Hg at the Screening Visit. 

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b. Congestive heart failure. 
c. Unstable angina or exacerbation of coronary artery disease within 6 months before 
the day of vaccination (Day 1) requiring cardiac intervention or new cardiac 
medications to control symptoms. 
d. Diabetes requiring the use of medicine (injectable or oral) or not controlled with diet. 
e. Chronic obstructive pulmonary disease, asthma requiring daily use of a 
bronchodilator or inhaled/systemic corticosteroids, or other chronic lung diseases 
such as pulmonary fibrosis. 
6. 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. 
7. Has a current or previous diagnosis of immunocompromising condition, 
immune-mediated disease, or other immunosuppressive condition. 
8. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days in 
total within 6 months prior to Screening Visit (for corticosteroids ≥ 10 mg/day of 
prednisone or equivalent) or is anticipating the need for immunosuppressive treatment at 
any time during participation in the study. 
9. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the IP. 
10. Has a history of coagulopathy or bleeding disorder considered a contraindication to IM 
injection or phlebotomy. 
11. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP injection, with 
the exception of vaccines authorized or approved for the prevention of COVID-19 
(regardless of type of vaccine) that become available to participants during the study. 
Efforts should be made to space study vaccination and COVID-19 vaccination by at least 
7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
12. Has received a seasonal influenza vaccine or any other investigational influenza vaccine 
after 01 Jan 2021. 
13. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive them during the study. 
14. Has a diagnosis of malignancy within the previous 10 years (excluding nonmelanoma 
skin cancer). 

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15. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
16. Has participated in an interventional clinical study within 28 days prior to the Screening 
Visit based on the medical history interview or plans to do so while participating in this 
study. 
17. Is an immediate family member or household member of study personnel, study site staff, 
or Sponsor personnel. 
5.2. 
Phase 2 Northern Hemisphere and Phase 2 Extension 
5.2.1. 
Inclusion Criteria 
Each participant must meet all of the following criteria at the Screening Visit and at Day 1, unless 
noted otherwise, to be enrolled in this study: 
1. Is an adult, ≥ 18 years of age at the time of consent (Screening Visit), who in the opinion 
of the Investigator, is medically stable based on review of medical history and physical 
examination performed at screening. Medically stable is defined as disease not requiring 
significant change in therapy or hospitalization for worsening disease during the 
3 months before enrollment. Participants may be rescreened if they are not medically 
stable at the Screening Visit. 
2. Understands and is willing and physically able to comply with protocol-mandated 
follow-up, including all procedures, in the opinion of the Investigator. 
3. Has provided written informed consent for participation in this study, including all 
evaluations and procedures as specified in this protocol. 
4. If female and is not of childbearing potential, may be enrolled in the study. The definition 
of a female of childbearing potential is provided in Appendix 2 (Section 11.2). An FSH 
level may be measured at the discretion of the Investigator to confirm postmenopausal 
status. 
5. If female and of childbearing potential, meets all of the following criteria to be enrolled 
in the study: 
• Has a negative pregnancy test at the Screening Visit and on the day of vaccination 
(Day 1). 
• Has practiced adequate contraception (Section 11.2) or has abstained from all 
activities that could result in pregnancy for at least 28 days prior to Day 1. 

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• Has agreed to continue adequate contraception through 3 months following vaccine 
administration. Adequate female contraception is defined as consistent and correct 
use of an FDA-approved contraceptive method in accordance with the product label. 
• Is not currently breastfeeding. 
5.2.2. 
Phase 2 Northern Hemisphere Exclusion Criteria 
Participant meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had close contact to someone with SARS-CoV-2 infection or COVID-19 as defined 
by the CDC (CDC 2021a) in the past 14 days prior to the Screening Visit, unless the 
participant has been fully vaccinated for COVID-19. 
2. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 
the 28-day screening window and will retain their initially assigned participant number. 
3. Has a medical, psychiatric, occupational condition, or history of substance abuse 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. 
4. Has a current or previous diagnosis of immunocompromising/immunosuppressive 
condition, immune-mediated disease requiring immune-modifying therapy, asplenia, 
recurrent severe infections (human immunodeficiency virus [HIV]-positive participants 
on antiretroviral therapy with cluster of differentiation [CD] 4 count ≥ 350 cells/mm3 and 
HIV-RNA ≤ 500 copies/mL within the past 12 months are permitted). 
5. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days in 
total within 6 months prior to the Screening Visit (for corticosteroids ≥ 10 mg/day of 
prednisone or equivalent) or is anticipating the need for systemic immunosuppressive 
treatment at any time during participation in the study. 
6. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the 
mRNA-1010 or the comparator vaccine, which is an egg-based influenza vaccine. 
7. Has coagulopathy or bleeding disorder considered a contraindication to IM injection or 
phlebotomy. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP vaccine 
injection, with the exception of vaccines authorized or approved for the prevention of 

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COVID-19 (regardless of type of vaccine) that become available to participants during 
the study. Efforts should be made to space study vaccination and COVID-19 vaccination 
by at least 7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
9. Has received a seasonal influenza vaccine or any other investigational influenza vaccine 
within 6 months prior to the Screening Visit. 
10. Had tested positive for influenza by CDC-recommended testing methods (CDC 2020c) 
within 6 months prior to the Screening Visit. 
11. Has received systemic immunoglobulins or blood products within 3 months prior to the 
Screening Visit or plans to receive them during the study. 
12. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
13. Has participated in an interventional clinical study within 28 days prior to the Screening 
Visit based on the medical history interview or plans to do so while participating in this 
study. 
14. Is an immediate family member or household member of study personnel, study site staff, 
or Sponsor personnel. 
5.2.3. 
Phase 2 Extension Exclusion Criteria 
Participant meeting any of the following criteria at the Screening Visit or at Day 1, unless noted 
otherwise, will be excluded from the study: 
1. Has had close contact to someone with SARS-CoV-2 infection or COVID-19 as defined 
by the CDC in the past 10 days prior to the Screening Visit. 
2. Is acutely ill or febrile (body temperature ≥ 38.0°C/100.4°F) 72 hours prior to or at the 
Screening Visit or Day 1. Participants meeting this criterion may be rescheduled within 
the 28-day screening window and will retain their initially assigned participant number. 
3. Has a medical, psychiatric, occupational condition, or history of substance abuse 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. 
4. Has a current or previous diagnosis of immunocompromising/immunosuppressive 
condition, immune-mediated disease requiring immune-modifying therapy, asplenia, 
recurrent severe infections (HIV-positive participants on antiretroviral therapy with CD 4 
count ≥ 350 cells/mm3 and HIV-RNA ≤ 500 copies/mL within the past 365 days are 
permitted). 

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5. Has received systemic immunosuppressants or immune-modifying drugs for > 14 days in 
total within 180 days prior to Screening Visit (for corticosteroids ≥ 10 mg/day of 
prednisone or equivalent) or is anticipating the need for systemic immunosuppressive 
treatment at any time during participation in the study. 
6. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine or any of the components contained in the 
mRNA-1010 or the comparator vaccine, which is an egg-based influenza vaccine. 
7. Has coagulopathy or bleeding disorder considered a contraindication to IM injection or 
phlebotomy. 
8. Has received or plans to receive any licensed vaccine ≤ 28 days prior to the IP injection 
(Day 1) or plans to receive a licensed vaccine within 28 days after the IP injection, with 
the exception of vaccines authorized or approved for the prevention of COVID-19 
(regardless of type of vaccine) that become available to participants during the study. 
Efforts should be made to space study vaccination and COVID-19 vaccination by at least 
7 and preferably 14 days, but COVID-19 vaccination should not be delayed. 
9. Has received a seasonal influenza vaccine or any other investigational influenza vaccine 
within 180 days prior to the randomization visit. 
10. Had tested positive for influenza by CDC-recommended testing methods within 180 days 
prior to the Screening Visit. 
11. Has received systemic immunoglobulins or blood products within 90 days prior to the 
Screening Visit or plans to receive them during the study. 
12. Has donated ≥ 450 mL of blood products within 28 days prior to the Screening Visit or 
plans to donate blood products during the study. 
13. Has participated in an interventional clinical study within 28 days prior to the Screening 
Visit based on the medical history interview or plans to do so while participating in this 
study. 
14. Is an immediate family member or household member of study personnel, study site staff, 
or Sponsor personnel. 
5.3. 
Lifestyle Restrictions 
Participants must not eat or drink anything hot or cold within 10 minutes before oral temperature 
is taken. Participants in the study should defer vaccination with licensed seasonal influenza vaccine 
until after completion of their Day 29 Visit, if seasonal influenza vaccine is available and they 
choose to receive it. 

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5.4. 
Screen Failures 
Screen failures are defined as participants who consent to participate in the clinical study but are 
not subsequently randomly assigned to treatment. A minimum set of screen failure information is 
required to ensure transparent reporting of screen failures to meet the Consolidated Standards of 
Reporting Trials publishing requirements and to respond to queries from regulatory authorities. 
Minimum information includes date of informed consent, demography, reason(s) for screen 
failure, and eligibility criteria. 

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6. 
STUDY TREATMENT 
6.1. 
Investigational Products Administered 
Investigational products in the Phase 1/2 part of the study are the mRNA-1010 vaccine candidate 
and placebo and those administered in the Phase 2 NH and Phase 2 Extension parts of the study 
are the mRNA-1010 vaccine candidate and licensed quadrivalent seasonal influenza vaccine 
(active comparator). 
In the Phase 1/2 part of the study, the mRNA-1010 vaccine to be tested includes mRNAs that 
encode for the surface glycoprotein HAs of the following influenza virus strains recommended by 
the WHO for 2020-2021 SH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Hong Kong/45/2019(H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
In the Phase 2 NH and Phase 2 Extension parts of the study, the mRNA-1010 vaccine to be tested, 
includes mRNAs that encode for the surface glycoprotein HAs of the following influenza virus 
strains recommended by the WHO for 2021-2022 NH cell- or recombinant-based vaccines: 
• A/Wisconsin/588/2019(H1N1)pdm09 
• A/Cambodia/e0826360/2020 (H3N2) 
• B/Washington/02/2019 (B/Victoria lineage) 
• B/Phuket/3073/2013 (B/Yamagata lineage) 
mRNA-1010 is formulated in LNPs composed of 4 lipids (1 proprietary and 3 commercially 
available): the proprietary ionizable lipid SM-102; cholesterol; 1,2-distearoyl-sn-glycero-
3-phosphocholine (DSPC); and 1-monomethoxypolyethyleneglycol-2,3-dimyristylglycerol with 
polyethylene glycol of average molecular weight 2000 (PEG2000-DMG). The mRNA-1010 
injection is provided as sterile liquid for injection and is a white to off-white dispersion at a 
concentration of 0.5 mg/mL (in the Phase 1/2 part) or 0.4 mg/mL (in the Phase 2 NH and Phase 2 
Extension parts) in 20 mM Tris buffer containing 87 mg/mL sucrose and 10.7 mM sodium acetate 
at pH 7.5. 
In each part of the study, the mRNA-1010 vaccine will be administered as a single 0.5-mL IM 
injection at total dose levels ranging from 6.25 to 200 µg to participants according to the 
vaccination group assignment (Table 7, Table 8, and Table 9). The placebo (administered in the 

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Phase 1/2 part only) is 0.9% Sodium Chloride (normal saline) Injection, which meets the criteria 
of the US Pharmacopeia (USP) (Table 7). 
Table 7 
Phase 1/2 - Summary of Vaccination Groups 
Vaccination 
Group 
Investigational Product 
Administered 
Dose 
Number of Participants 
1 
mRNA-1010 
50 µg 
45 
2 
mRNA-1010 
100 µg 
45 
3 
mRNA-1010 
200 µg 
45 
4 
Placebo 
− 
45 
The active comparator vaccine (administered in the Phase 2 NH and Phase 2 Extension parts only) 
will be administered as a single 0.5-mL IM injection to participants per the vaccination group 
assignment (Table 8 and Table 9). 
Table 8 
Phase 2 NH - Summary of Vaccination Groups 
Vaccination 
Group 
Investigational Product 
Administered 
Dose 
Number of Participants 
1 
mRNA-1010 
25 µg 
150 
2 
mRNA-1010 
50 µg 
150 
3 
mRNA-1010 
100 µg 
150 
4 
Licensed quadrivalent seasonal 
influenza vaccine  
(active comparator) 
60 µg 
50 
Table 9 
Phase 2 Extension - Summary of Vaccination Groups 
Vaccination 
Group 
Investigational Product 
Administered 
Dose 
Number of Participants 
1 
mRNA-1010 
6.25 µg 
50 
2 
mRNA-1010 
12.5 µg 
50 
3 
mRNA-1010 
25 µg 
50 
4 
Licensed quadrivalent seasonal 
influenza vaccine  
(active comparator) 
60 µg 
50 

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6.2. 
Randomization 
6.2.1. 
Phase 1/2 
The Sponsor’s Biostatistics Department or designee will generate the randomized allocation 
schedule(s) for vaccination group assignment. Overall, approximately 180 participants will be 
randomized in a 1:1:1:1 ratio to receive either mRNA-1010 50 μg, mRNA-1010 100 μg, 
mRNA-1010 200 μg, or placebo, with approximately 45 participants randomly assigned to each 
vaccination group. A total of 36 participants (9 participants in each vaccination group) will be 
randomly assigned in the initial stage of the study. A total of 144 participants (36 participants in 
each vaccination group) will be randomly assigned in the expansion stage of the study. 
Randomization in the expansion stage will be stratified by age (18 to < 50 years versus ≥ 50 years) 
and will be balanced across the 2 age groups within each vaccination group. 
6.2.2. 
Phase 2 Northern Hemisphere 
The Sponsor’s Biostatistics Department or designee will generate the randomized allocation 
schedule(s) for vaccination group assignment. Overall, approximately 500 participants will be 
randomly assigned in a 3:3:3:1 ratio to receive either mRNA-1010 25 μg, mRNA-1010 50 μg, 
mRNA-1010 100 μg, or licensed quadrivalent seasonal influenza vaccine (active comparator), 
with approximately 150 participants randomly assigned to each mRNA-1010 vaccination group 
and 50 participants to the Active Comparator Group. Randomization will be stratified by age 
(18 to < 50 years, 50 to < 65 years, or ≥ 65 years) and vaccination status in the previous flu season 
(received or not received). 
6.2.3. 
Phase 2 Extension 
The Sponsor’s Biostatistics Department or designee will generate the randomized allocation 
schedule(s) for vaccination group assignment. Overall, approximately 200 participants will be 
randomly assigned in a 1:1:1:1 ratio to receive either mRNA-1010 6.25 μg, mRNA-1010 12.5 μg, 
mRNA-1010 25 μg, or licensed quadrivalent seasonal influenza vaccine (active comparator), with 
approximately 50 participants randomly assigned to each mRNA-1010 vaccination group and 
50 participants to the Active Comparator Group. Randomization will be stratified by age 
(18 to < 50 years or ≥ 50 years), with at least 30% of participants in each dose group being 
≥ 50 years of age. 
6.3. 
Preparation/Handling/Storage/Accountability 
6.3.1. 
Preparation of Investigational Product 
In the study, the IP will be prepared for each participant based on the vaccination group. For the 
Phase 1/2 part, the mRNA-1010 vaccine injection will have a volume of 0.5 mL and will contain 

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mRNA-1010 at a dose of 50 µg (Vaccination Group 1), 100 µg (Vaccination Group 2), or 200 µg 
(Vaccination Group 3). For the Phase 2 NH part, the mRNA-1010 vaccine injection will have a 
volume of 0.5 mL and will contain mRNA-1010 at a dose of 25 µg (Vaccination Group 1), 50 µg 
(Vaccination Group 2), or 100 µg (Vaccination Group 3). For the Phase 2 Extension part, the 
mRNA-1010 vaccine injection will have a volume of 0.5 mL and will contain mRNA-1010 at a 
dose of 6.25 µg (Vaccination Group 1), 12.5 µg (Vaccination Group 2), or 25 µg (Vaccination 
Group 3). For Vaccination Group 4 in the Phase 1/2 part of the study, placebo will be administered 
at a volume of 0.5 mL. For Vaccination Group 4 in the Phase 2 NH part of the study, the active 
comparator will be administered at a volume of 0.5 mL. For Vaccination Group 4 in the Phase 2 
Extension part of the study, the active comparator will be administered at a volume of 0.5 mL. The 
IP (mRNA-1010, placebo, and active comparator) preparation instructions are detailed in the 
Pharmacy Manual. 
6.3.2. 
Investigational Product Administration 
The IP (mRNA-1010 or placebo during the Phase 1/2 part and mRNA-1010 or the active 
comparator during the Phase 2 NH and Phase 2 Extension parts) will be administered as a single 
IM injection into the deltoid muscle on Day 1. Preferably, the IP should be administered into the 
nondominant arm. 
Participants will be monitored for a minimum of 60 minutes after administration of the IP. 
Assessments will include vital sign measurements and monitoring for local or systemic reactions 
as shown in the SoE for Phase 1/2 (Table 1), Phase 2 NH (Table 2), and Phase 2 Extension (Table 
3) parts of the study. 
The study site will be appropriately staffed with individuals with basic cardiopulmonary 
resuscitation training/certification. Either onsite resuscitation equipment and personnel or 
appropriate protocols for the rapid transport of a participant to a resuscitation area or facility are 
required. 
6.3.3. 
Investigational Product Delivery and Receipt 
The Sponsor or designee is responsible for the following: 
• Supplying the IP (mRNA-1010, placebo, and active comparator). 
• Confirming the appropriate labeling of the IP for clinical study use, so that it 
complies with the US legal requirements. 
The Investigator is responsible for acknowledging 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. 

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• Confirming that the temperature during shipment from the Sponsor to the 
Investigator’s designated storage location was appropriate. 
• Confirming that the Sponsor has authorized the IP for use. 
• Ensuring the appropriate dose level of the IP is properly prepared using aseptic 
technique. 
Further description of the IP and corresponding instructions for the receipt, storage, preparation, 
administration, accountability, and destruction are described in the Pharmacy Manual. 
6.3.4. 
Investigational Product Packaging and Labeling 
The Sponsor will provide the Investigator (via the study site pharmacy) with adequate quantities 
of the IP. Sterile mRNA-1010 for the Phase 1/2 part is packaged in 2R glass vials with a 0.6-mL 
fill volume and that for the Phase 2 NH and Phase 2 Extension parts is packaged in 2R glass vials 
with a 0.8-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, USP for use as both placebo (Phase 1/2) and diluent for the 
mRNA-1010 vaccine (as applicable) as well as the active comparator (Phase 2 NH and Phase 2 
Extension). The 0.9% Sodium Chloride Injection, USP 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) 
guidelines, guidelines for Quality System Regulations, and applicable regulations. 
6.3.5. 
Investigational Product Storage 
mRNA-1010 must be stored at -60°C to -90°C (-76°F to -130°F) in a secure area with limited 
access and must be protected from moisture and light until it is prepared for administration 
(Section 6.3.1). The freezer should have automated temperature recording and a 24-hour alert 
system in place that allows for rapid response in case of freezer malfunction. There must be an 
available backup freezer. The freezer must be connected to a backup generator. In addition, for IP 
accountability, staff are required to keep a temperature log to establish a record of compliance with 
these storage conditions. The study 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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The active comparator should be stored in its original container and in accordance with the 
instructions in the Pharmacy Manual. 
6.3.6. 
Investigational Product Accountability 
The Investigator is responsible for ensuring that the IP accountability staff maintain accurate 
records in an IP accountability log of receipt of all IPs, 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 completion 
of the study. Additional details are provided in the Pharmacy Manual. 
6.3.7. 
Investigational Product Handling and Disposal 
A site monitor will reconcile the IP inventory during study conduct and at EoS for compliance. 
Once fully reconciled at the site at EoS, unused IP will be destroyed onsite or, if necessary, returned 
to the sending depot for destruction. 
6.4. 
Investigational Product Compliance 
The IP will be administered at the study site under direct observation of medically qualified study 
staff, and IP administration will be appropriately recorded (date and time) in the eCRF. Qualified 
staff will confirm that the participant has received the entire dose of the IP. If a participant does 
not receive the IP, the reason for the missed dose will be recorded. Data will be reconciled with 
site accountability records to assess compliance. 
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 1, Table 2, and 
Table 3). 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. 
6.5. 
Prior and Concomitant Medications 
6.5.1. 
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. 

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6.5.2. 
Concomitant Medications and Therapies 
At each study visit, study site 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 
IP injection and through Day 181/EoS. 
• Any seasonal influenza vaccine administered since September 2020 (Phase 2 NH) or 
since September 2021 (Phase 2 Extension). 
• Any authorized or investigational COVID-19 vaccine at any time before the IP 
injection and through Day 181/EoS. 
• All concomitant medications taken through 28 days after the IP injection. 
Antipyretics and analgesics taken prophylactically (ie, taken in the absence of any 
symptoms in anticipation of an injection reaction) will be recorded as such. 
• Systemic steroids (≥ 10 mg/day of prednisone or equivalent), immunosuppressants, 
immune-modifying drugs, immunoglobulins, and/or blood products administered at 
any time during the study period after the IP injection. 
• Any concomitant medications relevant to or for the treatment of an SAE, AESI, or an 
MAAE from Day 1 through Day 181/EoS. 
• 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 the study 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 study visits after 
vaccination or via other participant interactions (eg, telephone calls). 
Concomitant medications (including vaccinations) will be coded using the WHODrug Global. 
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 the study vaccination 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. 

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6.5.3. 
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 (see Table 14 for definition of PP Set): 
• 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 ≥ 10 mg/day of prednisone or 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 within 28 days after the study 
vaccination, except for any authorized or approved COVID-19 vaccine that was 
administered more than 14 days before or after the study vaccination (exclusion 
criterion No. 11; Section 5.1.2). 
• Immunoglobulins and/or any blood products administered during the study period. 
6.6. 
Intervention After End of the Study 
The IP will not be available to participants after the EoS. 

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7. 
DELAY OR DISCONTINUATION OF STUDY INTERVENTION AND 
PARTICIPANT DISCONTINUATION/WITHDRAWAL 
7.1. 
Pause Rules 
Study pause rules will be continuously monitored during all periods of the study by the 
Investigators, IST, and DSMB (as warranted). If the Investigator, IST, or DSMB request that the 
study be paused due to a safety concern, further study vaccination in the affected vaccination group 
and at higher dose levels will be suspended, but all other planned procedures relating to safety, 
reactogenicity, and immunogenicity assessments will continue as described in the protocol. The 
Sponsor will notify the Center for Biologics Evaluation and Research within 48 hours in the event 
of a study pause. 
7.1.1. 
Pause Rules for the Phase 1/2 Part of the Study 
7.1.1.1. 
Pause Rules Based on the Occurrence of a Single Event and Adjudicated by the 
Data and Safety Monitoring Board 
During the Phase 1/2 part of the study, the occurrence of any of the events listed in Table 10 
regardless of the vaccination group, will result in immediate suspension of dosing and enrollment 
in the vaccination group and at higher dose levels. An unscheduled DSMB will be convened to 
assess specific data concerns and to make recommendations. 
Table 10 Phase 1/2 Pause Rule Criteria, Events, and Thresholds - Single Event 
Pause 
Rule 
Event 
Number of 
Participants 
1 
Any SAE that cannot be reasonably attributed to a cause other 
than study vaccination 
≥ 1 
2 
Any Grade 4 AEa that cannot be reasonably attributed to a 
cause other than study vaccination 
≥ 1 
3 
Any systemic immediate hypersensitivity reaction within 
60 minutes after the study vaccination 
≥ 1 
Abbreviations: AE = adverse event; AR = adverse reaction; FDA = Food and Drug Administration; SAE = serious adverse event; 
US = United States. 
a Grade 4 AE includes any Grade 4 solicited local or systemic AR and any Grade 4 laboratory abnormality. Grading of 
laboratory parameters will be based on the US FDA Guidance for Industry “Toxicity grading scale for healthy adult and 
adolescent volunteers enrolled in preventive vaccine clinical trials” (DHHS 2007b). 
7.1.1.2. 
Pause Rules Based on the Occurrence of Events in a Proportion of Participants 
During the Phase 1/2 part of the study, the occurrence of safety events that will pause study dosing 
based on defined threshold levels, which are aggregate incidences relative to the number of 
exposed participants within a vaccination group, are summarized in Table 11. 

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Table 11 Phase 1/2 Pause Rule Criteria, Events, and Thresholds – Proportion of 
Participants 
Pause 
Rule 
Event 
Number or Percentage of Participantsa 
4 
Any Grade 3 solicited local AR lasting 
more than 48 hours, within the 7-day 
postvaccination period 
≥ 2b participants per group in the initial 
stage or ≥ 20% of participants in the 
expansion stage 
5 
Any Grade 3 solicited systemic AR 
lasting more than 48 hours (24 hours for 
fever) that cannot be reasonably 
attributed to a cause other than 
vaccination, within the 7-day 
postvaccination period 
≥ 2b participants per group in the initial 
stage or ≥ 20% of participants in the 
expansion stage 
6 
Any severe unsolicited AE in a 
vaccination group that cannot be 
reasonably attributed to a cause other 
than vaccination 
OR 
Any Grade 3 laboratory abnormalityc in 
a vaccination group that cannot be 
reasonably attributed to a cause other 
than vaccination 
≥ 2b participants per group in the initial 
stage or ≥ 20% of participants in the 
expansion stage 
Abbreviations: AE = adverse event; AR = adverse reaction; FDA = Food and Drug Administration; MedDRA = Medical 
Dictionary for Regulatory Activities; US = United States. 
a The rate of AEs and laboratory abnormalities will be computed based on the number of exposed participants who have 
provided safety data (ie, have completed a postdosing visit for assessment of safety). 
b For the first 9 participants in each vaccination group, the pause rule will be considered to be met if 2 of the first 9 participants 
experience the same solicited AR or the same MedDRA preferred term unsolicited AE or laboratory abnormality. The 
calculation for ≥ 20% of participants in the expansion stage includes participants in the initial stage and the expansion stage as 
the total number of participants in the denominator. 
c Grading of laboratory parameters will be based on the US FDA Guidance for Industry “Toxicity grading scale for healthy adult 
and adolescent volunteers enrolled in preventive vaccine clinical trials” (DHHS 2007b). 
If a pause is triggered in the study, each participant’s study site visits will continue until EoS. If a 
pause affects a participant’s vaccination visit, the window for that participant’s vaccination visit 
will be suspended until the pause is lifted and vaccination can resume. Once the pause is lifted, 
vaccination should be reinstated as soon as possible. 
If a participant is in the screening period for more than 28 days as the result of a pause, the 
participant may be rescreened for study eligibility (and will receive a new screening number) as 
long as the participant continues to provide consent to participate in the study. 
7.1.2. 
Pause Rules for the Phase 2 Northern Hemisphere and the Phase 2 Extension 
Parts of the Study 
During the Phase 2 parts of the study, the occurrence of any of the events listed in Table 12 
regardless of the vaccination group, will result in immediate suspension of dosing and enrollment 

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in the vaccination group and at higher dose levels. An unscheduled DSMB will be convened to 
assess specific data concerns and to make recommendations. 
Table 12 Phase 2 Northern Hemisphere and Phase 2 Extension Pause Rule Criteria, 
Events, and Thresholds - Single Event 
Pause 
Rule 
Event 
Number of 
Participants 
1 
Any SAE that cannot be reasonably attributed to a cause other 
than study vaccination 
≥ 1 
2 
Any Grade 4 solicited local or systemic AR that cannot be 
reasonably attributed to a cause other than study vaccination 
≥ 1 
3 
Any systemic immediate hypersensitivity reaction within 
60 minutes after the study vaccination 
≥ 1 
Abbreviations: AR = adverse reaction; SAE = serious adverse event. 
7.2. 
Criteria for Delay or Withholding of Study Vaccination 
Body temperature must be measured at the dosing visit before vaccine administration. The 
following events constitute criteria for delay of injection, and if either of these events occur at the 
time scheduled for dosing, the participant may be injected at a later date within the time window 
specified in the SoE (Table 1, Table 2, and Table 3): 
• Acute moderate or severe infection with or without fever at the time of dosing. 
• Fever, defined as body temperature ≥ 38.0°C (100.4°F) at the time of dosing. 
• Receipt of COVID-19 vaccination within 7 to 14 days of planned Day 1. 
Participants with a minor illness without fever, as assessed by the Investigator, can be vaccinated. 
Participants with a fever ≥ 38.0°C (100.4°F) will be contacted within the time window acceptable 
for participation and reevaluated for eligibility. If the Investigator determines that the participant’s 
health on the day of dosing temporarily precludes injection, the visit should be rescheduled within 
the allowed interval for that visit. 
The Investigator, in consultation with the Sponsor’s medical monitor, may withhold the IP 
injection if the participant meets any of the following criteria: 
• Becomes pregnant. 
• Develops symptoms or conditions listed in the exclusion criteria. 
• Experiences a clinically significant change in clinical laboratory test results, vital sign 
measurements, or general condition that, in the judgment of the Investigator, requires 
withholding of vaccine. 

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The reason(s) for withholding the injection will be recorded in the eCRF. 
If a participant takes a prohibited drug therapy, the Investigator could delay the IP injection within 
the visit window or withhold the IP injection based on a joint decision of the Investigator and the 
CRO’s medical monitor (Section 6.5.3). 
7.3. 
Participant Discontinuation/Withdrawal From the Study 
Participants who withdraw or are withdrawn from the study will not be replaced unless otherwise 
stated in the protocol. 
A “withdrawal” from the study refers to a situation wherein a participant does not return for the 
final visit planned in the protocol. 
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 section of the 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) 
• SAE (specify) 
• Solicited AR or reactogenicity event (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) 

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Participants who are withdrawn from the study because of AEs (including SAEs, solicited ARs, 
or reactogenicity events) 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 AE, SAE, solicited AR, or reactogenicity event 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 (Section 11.1.6). 
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). 
7.4. 
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 study site 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. 
• 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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8. 
STUDY ASSESSMENTS AND PROCEDURES 
Before performing any study procedures, all potential participants will sign an informed consent 
form (ICF; Section 11.1.6). Participants will undergo study procedures at the time points specified 
in the SoE (Table 1, Table 2, and Table 3). A participant can also be seen for an unscheduled visit 
at any time during the study. Reasons for an unscheduled visit may include, but are not limited to, 
reactogenicity issues, symptoms of potential ILI, and/or 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. 
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 1, Table 2, and Table 3). 
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. 
• The Screening Visit and Day 1 Visit cannot be completed on the same day for the 
Phase 1/2 part but may be completed on the same day for the Phase 2 NH and Phase 2 
Extension parts. Additionally, the Screening Visit may be performed over multiple 
visits if within the 28-day screening window. 

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8.1. 
Safety Assessments and Procedures 
Safety assessments will include monitoring and recording of the following for each participant, 
according to the SoE (Table 1, Table 2, and Table 3): 
• Solicited local and systemic ARs (Section 8.4.3) that occur during the 7 days 
following vaccine administration (ie, the day of injection and 6 subsequent days). 
Solicited ARs will be recorded daily using eDiaries (Section 8.1.1). 
• Unsolicited AEs observed or reported during the 28 days following vaccine 
administration (ie, the day of injection and 27 subsequent days). Unsolicited AEs are 
defined in Section 8.4.1. 
• AEs leading to discontinuation from study participation from Day 1 through 
Day 181/EoS or withdrawal from the study. 
• MAAEs from Day 1 through Day 181/EoS or withdrawal from the study. 
• SAEs and AESIs from Day 1 through Day 181/EoS or withdrawal from the study. 
• Results of safety laboratory tests (Phase 1/2 only; Section 8.1.3). 
• Vital sign measurements (Section 8.1.4). 
• Physical examination findings (Section 8.1.5). 
• Assessments for causes of respiratory infections as needed from Day 1 through 
Day 181/EoS in the Phase 1/2 and Phase 2 Extension parts of the study or withdrawal 
from the study (Section 8.1.6). Active and passive surveillance for ILI (and 
assessments for causes of respiratory infections as needed) will be conducted from 
Day 1 through Day 181/EoS in the Phase 2 NH part of the study. 
• Details of all pregnancies in female participants will be collected after the study 
vaccination on Day 1 and until the end of their participation in the study 
(Section 8.4.8). 
• Optional blood sample collection on Day 4 in the Phase 2 Extension part. 
8.1.1. 
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 own device or using a device that is provided at 
the time of enrollment. Before enrollment on Day 1, the participants will be instructed to download 
the eDiary application or will be provided an eDiary device to record solicited ARs (Section 8.4.3). 
Participants in the Phase 2 NH part of the study will also use the eDiary to record any ILI symptoms 

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(as part of active and passive surveillance) that they experience after vaccination from Day 1 
through Day 181/EoS. 
Participants will be instructed on Day 1 on thermometer usage to measure body temperature, ruler 
usage to measure injection site erythema and swelling/induration (hardness), and self-assessment 
for localized axillary swelling or tenderness on the same side as the injection arm. 
Participants will record data into the eDiary starting approximately 1 hour after 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 8.4.3, that 
occur on the day of IP administration and during the 7 days after the IP administration 
(ie, the day of injection and 6 subsequent days). Any solicited AR that continues 
beyond Day 7 will be reported in the eDiary until it is no longer reported but only 
until 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. 
• Passive and active surveillance of ILI (Phase 2 NH part only; Section 8.1.6). 
Participants will record symptoms of ILI that they may experience anytime from 
Day 1 through Day 181/EoS as part of the passive ILI surveillance. For active ILI 
surveillance, participants will be instructed to report whether ILI symptoms have been 
experienced, 3 to 4 times weekly from Day 1 through Day 29 and twice weekly from 
Day 30 through Day 181/EoS, via eDiary or telephone calls. If symptoms occur, 
participants will be directed to return to the study site as soon as possible, but no later 
than 72 hours after the onset of symptoms, for medical evaluation and an NP swab. 
Participants will be contacted by the study site, if they have missed reporting in the 
eDiary. If there is no response to an eDiary prompt for 2 consecutive entries, the 
study site staff will contact the participant by telephone (Section 8.1.6). 
• 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. 

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• 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 the day of injection 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. 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. 
Study site staff will review eDiary data with participants at a visit 7 days after the injection. 
8.1.1.1. 
Ancillary Supplies for Participant Use 
Study sites will distribute Sponsor-provided oral thermometers and rulers for use by participants 
in assessing body temperature and injection site reactions, for recording solicited ARs in eDiaries. 
Based on availability, smartphone devices may be provided to those participants who do not have 
their own device to use for eDiary activities. 
8.1.2. 
Safety Telephone Calls 
A safety telephone call is a telephone call made to the participant by trained site personnel. This 
call will follow a script, which will facilitate the collection of relevant safety information. Safety 
telephone calls follow a schedule for each participant, as shown in the SoE (Table 1, Table 2, and 
Table 3). The participant will be interviewed according to the script about occurrence of AEs, 
MAAEs, SAEs, AESIs, AEs leading to withdrawal from study participation, concomitant 
medications associated with those events, and any nonstudy vaccinations (Section 8.4.9). All 
safety information collected from the telephone contact must be documented in source documents 
as described by the participant and not documented on the script used for the safety telephone 
contact. An unscheduled follow-up safety call may be triggered if an eDiary record results in 
identification of a relevant safety event. 
8.1.3. 
Safety Laboratory Assessments 
In the Phase 1/2 part of the study, planned blood sampling for safety laboratory assessments will 
occur as indicated in the SoE (Table 1). Tests will include WBC count, hemoglobin, platelets, 
ALT, AST, total bilirubin, alkaline phosphatase, and creatinine. Laboratory tests will be performed 
by the central laboratory, unless otherwise specified. 
Pregnancy testing (applicable for all parts of the study) include the following: 

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• A point-of-care urine pregnancy test will be performed at the Screening Visit and 
before the study vaccination on Day 1. At any time, a pregnancy test either via blood 
or point-of-care urine can be performed, at the discretion of the Investigator. 
• If not documented in a female participant’s medical records, an FSH test may be 
performed at the Screening Visit, as necessary and at the discretion of the 
Investigator, to confirm postmenopausal status. 
No scheduled safety laboratory assessments (except for pregnancy testing) will be conducted in 
the Phase 2 NH or Phase 2 Extension parts of the study. 
8.1.4. 
Vital Sign Measurements 
Vital sign measurements will include systolic and diastolic BP, 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 1, Table 2, and Table 3). On the day of IP administration, vital sign measurements will 
be collected once before injection and approximately 1 hour after injection (before participants are 
discharged from the study site). Vital signs may be collected at other study visits in conjunction 
with a symptom-directed physical examination. 
If any of the vital sign measurements meet the toxicity grading criteria for clinical abnormalities 
of Grade 3 or greater, the abnormal value and grade will be documented in the AE section of the 
eCRF (unless there is another known cause of the abnormality that would result in an AE 
classification). The Investigator will continue to monitor the participant with additional 
assessments until the vital sign value has reached the reference range, returns to the vital sign value 
at baseline, is considered stable, or until the Investigator determines that follow-up is no longer 
medically necessary. 
Febrile participants on the day of IP administration (fever is defined as a body temperature 
≥ 38.0°C/100.4°F) may be rescheduled within the relevant window periods. Afebrile participants 
with minor illnesses may be injected at the discretion of the Investigator. 
When procedures overlap and are scheduled to occur at the same time point, the order of 
procedures should be vital sign measurements and then blood collection. 
8.1.5. 
Physical Examinations 
A full physical examination, including height and weight, will be performed at scheduled time 
points as indicated in the SoE (Table 1, Table 2, and Table 3). The full examination will include 
assessment of skin, head, ears, eyes, nose, throat, neck, thyroid, lungs, heart, cardiovascular 

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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, prior to injection, both arms and associated lymph 
nodes should be examined, and any abnormalities should be documented. 
Body mass index will be calculated at the Screening Visit only. 
8.1.6. 
Assessments for Respiratory Viral Infections 
Due to the ongoing COVID-19 pandemic, participants may get infected with SARS-CoV-2 or 
experience symptoms consistent with ILI during the study. 
Phase 1/2 
All participants will provide NP swab samples before the injection on Day 1 for assessment of 
asymptomatic infection with respiratory pathogens, including influenza virus and SARS-CoV-2, 
as influenza or COVID-19 symptoms may confound reactogenicity assessment (CDC 2020b). 
A study site visit or a consultation will be arranged within 24 hours or as soon as possible to collect 
an NP swab sample if a participant experiences symptoms consistent with the CDC definition of 
ILI (see Section 8.4.6 for definition) and/or COVID-19 during the course of the study. The NP 
swab sample will be tested by multiplex RT-PCR for respiratory pathogens, including influenza 
viruses and SARS-CoV-2. Additionally, clinical information may be collected to evaluate the 
severity of the clinical case. All findings will be recorded in the eCRF. 
If scheduled, a study site illness visit may include additional assessments such as medical history, 
physical examination, and blood sampling for clinical laboratory testing. Radiologic imaging 
studies may be conducted. Blood samples will be collected for potential future immunologic 
assessment of influenza and/or SARS-CoV-2 infection. 
If participants are confirmed to have SARS-CoV-2 infection during the study and are 
asymptomatic, the Investigator will notify the participant's primary care physician and local health 
authority, per local regulations. If the participant had known exposure to COVID-19 (eg, exposure 
to someone with a confirmed case of COVID-19) prior to Day 1, it will be captured on the 
COVID-19 exposure form, and the IP administration for that participant will be delayed for at least 
14 days. 
All cases of RT-PCR-confirmed ILI and/or COVID-19 should be captured as MAAEs (unless the 
definition for an SAE is met) along with relevant concomitant medications and details about 
severity, seriousness, and outcome. 

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Phase 2 Northern Hemisphere 
Participants in the Phase 2 NH part who manifest protocol-defined ILI (see Section 8.4.6 for 
definition) between Day 1 through Day 29 will be evaluated by real-time RT-PCR testing of an 
NP specimen for influenza (and other respiratory pathogens). 
Both active and passive surveillance for ILI (see Section 8.4.6 for ILI definitions) will be 
conducted between Day 1 through Day 181/EoS. For active surveillance, participants will be 
instructed to report whether ILI symptoms have been experienced, 3 to 4 times weekly from Day 1 
through Day 29, and twice weekly from Day 30 through Day 181/EoS, via eDiary or telephone 
calls.  
If symptoms occur, participants will be directed to return to the study site as soon as possible, but 
no later than 72 hours after the onset of symptoms, for medical evaluation and an NP swab. 
Participants will be contacted by the study site, if they have missed reporting in the eDiary. If there 
is no response to an eDiary prompt for 2 consecutive entries, the study site staff will contact the 
study participant by telephone. For passive surveillance, participants will be instructed to report 
symptoms of ILI any time from Day 1 through Day 181/EoS. 
Participants who manifest protocol-defined ILI (see Section 8.4.6 for definition) will have a study 
site visit or a consultation (unscheduled study visit) arranged within 72 hours after the onset of 
symptoms to collect an NP swab sample if participants experience symptoms consistent with the 
US CDC definition of ILI and/or COVID-19 during the course of the study. 
Phase 2 Extension 
For the Phase 2 Extension part, a study site visit or a consultation (unscheduled study visit) will 
be arranged within 72 hours after the onset of symptoms to collect an NP swab sample if 
participants experience symptoms consistent with the US CDC definition of ILI and/or COVID-19 
during the course of the study. 
8.2. 
Immunogenicity Assessments 
Blood samples for immunogenicity assessments will be collected at the time points indicated in 
the SoE (Table 1, Table 2, and Table 3). The following assessments are planned: 
• Serum antibody level as measured by HAI assay (primary, secondary, and 
exploratory endpoints). 
• Serum neutralizing antibody level as measured by microneutralization assay or 
similar method (secondary [Phase 1/2 part only] and exploratory endpoints). 

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• Cellular immunogenicity, in a subset of participants (Phase 1/2 cohort only), as 
assessed by flow cytometry/intracellular cytokine staining and/or enzyme-linked 
immune absorbent spot (exploratory endpoint). 
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, and unique sample identification will be utilized to maintain the 
blind at the laboratory at all times and to allow for automated sample tracking and housing. 
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 antibody levels will be performed in a laboratory designated by the Sponsor. 
According to the ICF (Section 11.1.6), 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 influenza viruses, additional assay development, and the immune response 
across influenza viruses. 
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. 
8.3. 
Efficacy Assessments 
While the study will not be powered for efficacy assessments, ILI will be tracked as an exploratory 
objective in the Phase 1/2, Phase 2 NH, and Phase 2 Extension parts of the study. Active and 
passive surveillance for influenza will be performed and assessed as part of an exploratory 
objective in the Phase 2 NH part. 
8.4. 
Safety Definitions and Related Procedures 
8.4.1. 
Adverse Event 
An AE is defined as any untoward medical occurrence associated with the use of a drug/vaccine 
in humans, whether or not considered related to the drug/vaccine. 

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Events Meeting the Adverse Event Definition 
• Exacerbation of a chronic or intermittent pre-existing condition, including an increase 
in frequency and/or intensity of the condition, after the IP injection. 
• New conditions detected or diagnosed after the IP injection 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 8.4.3). For the purposes of IND 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 vaccine administration). 
8.4.2. 
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 
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 1 overnight stay for observation and/or 

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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 AEs; 
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) that 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 1 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. 
8.4.3. 
Solicited Adverse Reactions 
The term “reactogenicity” refers to the occurrence and intensity of selected signs and symptoms 
(ARs) occurring after the IP injection. The eDiary will solicit daily participant reporting of ARs 
using a structured checklist (Section 8.1.1). Participants will record such occurrences in an eDiary 
on the day of injection and for the 6 days after the day of injection. 
Severity grading of reactogenicity will occur automatically based on participant entries into the 
eDiary according to the grading scales presented in Table 13, which are modified from the toxicity 
grading scale for healthy adult and adolescent volunteers enrolled in preventive vaccine clinical 
trials (DHHS 2007b). 
If a participant reported a solicited AR during the solicited period and did not record the event in 
the eDiary, the event should be recorded on the Reactogenicity page of the eCRF. 

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If the event starts during the solicited period, but continues beyond 7 days after dosing, the 
participant should notify the site to provide an end date to close out the event on the Reactogenicity 
page of the eCRF. 
If the participant reported an event after the solicited period (ie, after Day 7), it should be recorded 
as an AE on the AE page of the eCRF. 
All solicited ARs (local and systemic) will be considered causally related to study vaccination. 
Table 13 Solicited Adverse Reactions and Grades 
Reaction 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Injection site pain 
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 - 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 - 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 
No interference 
with activity 
Repeated use of 
over-the-counter 
(nonnarcotic) 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 
No interference 
with activity 
Repeated use of 
over-the-counter 
pain reliever 
> 24 hours or some 
interference with 
activity 
Significant; any 
use of prescription 
pain reliever or 
prevents daily 
activity 
Requires 
emergency room 
visit or 
hospitalization 
Fatigue 
No interference 
with activity  
Some interference 
with activity 
Significant; 
prevents daily 
activity  
Requires 
emergency room 
visit or 
hospitalization 

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Reaction 
Grade 1 
Grade 2 
Grade 3 
Grade 4 
Myalgia (muscle 
aches all over 
body) 
No interference 
with activity  
Some interference 
with activity 
Significant; 
prevents daily 
activity  
Requires 
emergency room 
visit or 
hospitalization 
Arthralgia (joint 
aches in several 
joints) 
No interference 
with activity  
Some interference 
with activity 
Significant; 
prevents daily 
activity  
Requires 
emergency room 
visit or 
hospitalization 
Nausea/vomiting 
No interference 
with activity or 1 
or 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 
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 - 38.4°C 
100.4°F - 101.1°F 
38.5°C - 38.9°C 
101.2°F - 102.0°F 
39.0°C - 40.0°C 
102.1°F - 104.0°F 
> 40.0°C 
> 104.0°F 
Abbreviations: AE = adverse event; eCRF = electronic case report form, 
Note: Events listed above but starting > 7 days post study injection will be recorded on the AE page of the eCRF. 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 in the solicited AR section 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 8.4.4). 
• 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). 
• Solicited local or systemic AR lasting beyond 7 days after injection. 
• Solicited local or systemic AR that otherwise meets the definition of an SAE. 
8.4.4. 
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, and/or COVID-19 

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[Section 8.1.6]) 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 recorded in the AE section of the eCRF. 
All cases of RT-PCR-confirmed ILI and/or confirmed COVID-19 will be recorded as MAAEs. 
8.4.5. 
Anaphylaxis 
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 8.4.13. 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 described below) should be reported 
as a potential case of anaphylaxis. This is provided as general guidance for Investigators and is 
based on the Brighton Collaboration case definition (Rüggeberg et al 2007). 
Anaphylaxis is an acute hypersensitivity reaction with multi-organ system involvement that can 
present as, or rapidly progress to, a severe life-threatening reaction. It may occur following 
exposure to allergens from a variety of sources. 
Anaphylaxis is a clinical syndrome characterized by 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, red and itchy eyes. 
− Cardiovascular: measured hypotension, clinical diagnosis of uncompensated shock, 
loss of consciousness or decreased level of consciousness, evidence of reduced 
peripheral circulation. 
− Respiratory: bilateral wheeze (bronchospasm), difficulty breathing, stridor, upper 
airway swelling (lip, tongue, throat, uvula, or larynx), respiratory distress, persistent 
dry cough, hoarse voice, sensation of throat closure, sneezing, rhinorrhea. 
− Gastrointestinal: diarrhea, abdominal pain, nausea, vomiting. 

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8.4.6. 
Influenza-Like Illness 
A protocol-defined ILI is determined by the occurrence of at least 1 respiratory illness symptom 
concurrently with at least 1 systemic symptom, or the occurrence of any 2 or more respiratory 
symptoms. 
Respiratory Symptoms 
Systemic Symptoms 
1. Sore throat 
2. Cough/rhinorrhea/nasal congestion (≥ 1 of 
the 3 symptoms count as 1 respiratory 
symptom) 
3. Sputum production 
4. Wheezing 
5. Difficulty breathing 
1. Body temperature > 37.2°C (> 99°F) 
2. Chills 
3. Tiredness 
4. Headache 
5. Myalgia 
6. Nausea/Vomiting 
7. Diarrhea  
A CDC-defined ILI is defined as body temperature ≥ 37.8°C (100°F) accompanied by cough 
and/or sore throat. 
An RT-PCR-confirmed ILI is defined as a positive influenza result by RT-PCR done at any setting 
during the study period. 
8.4.7. 
Adverse Events 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 are required. Such events may require further investigation to 
characterize and understand them. 
Adverse events of special interest for this protocol are listed in Appendix 3 (Section 11.3). 
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 
participant or receives updated information on a previously reported AESI at a time after the eCRF 
has been taken offline, then the site can report this information on a paper AESI form using the 
SAE Mailbox. 
Myocarditis/Pericarditis 
A case of suspected, probable, or confirmed myocarditis, pericarditis, or myopericarditis should 
be reported as an AESI, even if it does not meet criteria per the CDC case definition. The event 

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should also be reported as an SAE if it meets seriousness criteria (Section 8.4.2). The CDC case 
definition is provided in Section 11.4 as guidance. 
8.4.8. 
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 Day 1 should not receive the IP. 
Details of all pregnancies in female participants will be collected after the study vaccination on 
Day 1 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) are considered SAEs. 
Pregnancies occurring in participants after enrollment must be reported to Sponsor or designee 
within 24 hours of the site learning of its occurrence, using the SAE Mailbox, the SAE Hotline, or 
the SAE Fax line (Section 8.4.13). If the participant agrees to submit this information, the 
pregnancy must be followed to determine the outcome, including spontaneous or voluntary 
termination, details of the birth, and the presence or absence of any birth defects, congenital 
abnormalities, or maternal and/or newborn complications. This follow-up should occur even if 
intended duration of the safety follow-up for the study has ended. Pregnancy report forms will be 
distributed to the study site to be used for this purpose. The Investigator must immediately (within 
24 hours of awareness) report to the Sponsor any pregnancy resulting in an abnormal outcome 
according to the procedures described for SAEs. 
8.4.9. 
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 the vaccine dose. Other 
(unsolicited) AEs will be collected from Day 1 through 28 days after the vaccine dose. 
The MAAEs, SAEs, and AESIs will be collected from participants as specified in the SoE (Table 1, 
Table 2, and Table 3) until the end of their participation in the study. Any AEs occurring before 
receipt of the IP will be analyzed separately from AEs. 
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 respiratory viral infection 
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. 

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In addition to participant observations, physical examination findings and other documents 
relevant to participant safety classified as an AE will be documented in the AE section of the 
eCRF. 
After the initial AE/SAE report, the Investigator is required to proactively follow each participant 
at subsequent visits/contacts. All AEs and SAEs will be treated as medically appropriate and 
followed until resolution, stabilization, the event is otherwise explained, or the participant is LTFU 
(as defined in Section 7.4). 
8.4.10. 
Assessment of Intensity 
An event is defined as “serious” when it meets at least 1 of the predefined outcomes as described 
in the definition of an SAE (Section 8.4.2), 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 2007b) will be used to categorize local and systemic 
reactogenicity events (solicited ARs), clinical laboratory test results, and vital sign measurements 
observed during this study. Specific criteria for local and systemic reactogenicity events are 
presented in Section 8.4.3. 
The determination of severity for all unsolicited AEs should be made by the Investigator based 
upon medical judgment and the definitions of severity as follows: 
• Mild: These events do not interfere with the participant’s daily activities. 
• Moderate: These events cause some interference with the participant’s daily activities 
and require limited or no medical intervention. 
• Severe: These events prevent the participant’s daily activity and require intensive 
therapeutic intervention. 
Study staff should elicit from the participant the impact of AEs on the participant’s activities of 
daily living to assess severity and document appropriately in the participant’s source 
documentation. Changes in the severity of an AE should be documented in the participant’s source 
documentation to allow an assessment of the duration of the event at each level of intensity to be 
performed. An AE characterized as intermittent requires documentation of onset and duration of 
each episode. An AE that fluctuates in severity during the course of the event is reported once in 
the eCRF at the highest severity observed. 
8.4.11. 
Assessment of Causality 
The Investigator’s assessment of an AE’s relationship to the IP is part of the documentation process 
but is not a factor in determining what is or is not reported in the study. 

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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 the temporal sequence of 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. 
8.4.12. 
Reporting Adverse Events 
The Investigator is responsible for reporting all AEs that are observed or reported during the study 
regardless of their relationship to the 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 in the AE section 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 the IP, time of 
resolution of the event, seriousness, any required treatment or evaluations, and outcome. The 
unsolicited AEs resulting from concurrent illnesses, reactions to concurrent illnesses, reactions to 
concurrent medications, or progression of disease states must also be reported. All AEs will be 
followed until they are resolved or stable or judged by the Investigator to be not clinically 
significant. The Medical Dictionary for Regulatory Activities (MedDRA) will be used to code all 
unsolicited AEs. 
Any medical condition that is present at the time that the participant is screened but does not 
deteriorate should not be reported as an unsolicited AE. However, if it deteriorates at any time 
during the study, it should be recorded as an unsolicited AE. 
8.4.13. 
Reporting Serious Adverse Events 
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 8.4.2) must be 
reported to the Sponsor immediately (within 24 hours of becoming aware of the SAE) via the EDC 

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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: 
 
• SAE Hotline (USA): 
 
• SAE Fax Line (USA):
 
Regulatory reporting requirements for SAEs are described in Section 8.4.18. 
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 the IP or study procedures, or that caused 
the participant to discontinue the study. 
8.4.14. 
Reporting of Adverse Events of Special Interest 
The following process for reporting an AESI ensures compliance with 21 CFR 312 and ICH GCP 
guidelines. After learning that a participant has experienced an AESI, the Investigator or designee 
is responsible for reporting the AESI to the Sponsor, regardless of relationship or expectedness, 
within 24 hours of becoming aware of the event. If the AESI meets the criteria for an SAE, the 
SAE reporting procedure should be followed. 
8.4.15. 
Time Period and Frequency for Collecting Adverse Event and Serious Adverse 
Event Information 
Medical occurrences that begin before the start of 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. 
PPD
PPD
PPD

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Solicited ARs will be collected from the day of injection through 6 days after the injection. Other 
(unsolicited) AEs will be collected from the day of injection through 28 days after the injection. 
Serious AEs will be collected from the start of IP administration until the last day of study 
participation. 
All SAEs 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 from a study participant or receives updated data on a 
previously reported SAE and the eCRF has been taken offline, then the site can report this 
information on a paper SAE form using the SAE Mailbox, the SAE Hotline, or the SAE Fax line 
(Section 8.4.13). 
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, 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. 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. 
Participants who develop ILI will be followed through 30 days from the onset of ILI even if Day 30 
is beyond Day 181/EoS. 
8.4.16. 
Method of Detecting Adverse Events and Serious Adverse Events 
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 
the recording of information 
on 
other AEs 
(unsolicited AEs) and concomitant 
medications/vaccinations. 
The Investigator is responsible for the documentation of AEs regardless of the vaccination group 
or suspected causal relationship to the 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, which requires 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. 

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8.4.17. 
Follow-Up of Adverse Events and Serious Adverse Events 
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 7.4. 
8.4.18. 
Regulatory Reporting Requirements for Serious Adverse Events 
Prompt notification by the Investigator to the Sponsor of an SAE is essential so that legal 
obligations and ethical responsibilities towards the safety of participants and the safety of a study 
intervention under clinical investigation are met. 
The Sponsor has a legal responsibility to notify both the local regulatory authority and other 
regulatory agencies about the safety of a study intervention under clinical investigation. The 
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. 
8.5. 
Safety Monitoring 
The CRO’s medical monitor, the Sponsor’s medical monitor, and the individual Site Investigators 
will monitor safety throughout the study. The roles of the IST and DSMB are outlined in 
Section 11.1.11. 
8.6. 
Treatment of Overdose 
Because the IP is to be administered by an HCP, it is unlikely that an overdose will occur. Dose 
deviations will be tracked as protocol deviations (Section 11.1.8). 
8.7. 
Pharmacokinetics 
Pharmacokinetic parameters are not evaluated in this study. 
8.8. 
Pharmacodynamics 
Pharmacodynamic parameters are not evaluated in this study. 

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8.9. 
Biomarkers 
Immunogenicity assessments are described in Section 8.2. Biomarkers are not evaluated in the 
Phase 1/2 part of the study outside of the described immunogenicity assessments. Biomarker 
assessments (to be determined) will be evaluated in the Phase 2 NH and Phase 2 Extension parts 
of the study, which may include genomic and transcriptomic studies. 
8.10. 
Health Economics 
Health economics are not evaluated in this study. 

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9. 
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 but prior to any 
data unblinding, 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. 
9.1. 
Blinding and Responsibility for Analyses 
This 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 study database 
is locked and unblinded, with the following exceptions: 
• Unblinded personnel (of limited number) will be assigned to vaccine accountability 
procedures and will prepare the IP for all participants. These personnel will have no 
study functions other than IP management, documentation, accountability, 
preparation, and administration. They will not be involved in participant evaluations 
and will not reveal the identity of the 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. 
• An independent unblinded statistical and programming team will perform the 
preplanned IA (Section 9.6). Sponsor team members will be prespecified to be 
unblinded to the IA results and will not communicate the results to the blinded 
Investigators, study site staff, clinical monitors, or participants. 
• The DSMB will review the IA data to safeguard the interests of clinical study 
participants and to help ensure the integrity of the study. The DSMB will review 
unblinded IA results provided by the independent unblinded statistician. The DSMB 
will also review unblinded statistical outputs for ad hoc safety reviews triggered by 

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pause rules, should this occur. Section 11.1.11 provides additional information on 
DSMB and safety review. 
The dosing assignment will be concealed by having the unblinded pharmacy personnel prepare the 
IP in a secure location that is not accessible or visible to other study staff. An opaque sleeve over 
the syringe used for injection will maintain the blind at the time of injection, as the doses containing 
mRNA-1010 will look different from those of placebo/active comparator. Only delegated 
unblinded study site staff will conduct the injection procedure. Once the injection is completed, 
only the blinded study staff will perform further assessments and interact with the participants. 
Access to the randomization code will be strictly controlled at the pharmacy. 
9.1.1. 
Breaking the Blind 
Except in the case of medical necessity, a participant’s vaccine 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 vaccine assignment will affect that 
participant’s clinical management. In the event of a medical emergency requiring identification of 
individual vaccine assignment, the Investigator will make every attempt to contact the CRO’s 
medical monitor, preferably via electronic protocol inquiry platform, 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 interactive response 
technology (IRT). All unblinding instances will be tracked via an audit trail in IRT and documented 
in the final study report. 
In addition to the aforementioned situations where the blind may be broken, the data will also be 
unblinded to a statistical team at specified time point(s) for analysis as outlined in Section 9.6. 
9.2. 
Statistical Hypotheses 
No formal hypotheses will be tested. 
9.3. 
Sample Size Determination 
The sample size for this study 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 different dose levels of mRNA-1010. 
Phase 1/2 
Approximately 180 participants will be randomly assigned in this part of the study, with 
approximately 45 participants in each vaccination group. Details regarding the number of 
participants in each vaccination group and the randomization ratio are presented in Section 6.2.1. 

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With 45 participants receiving an investigational vaccine, there is a probability of approximately 
90% to observe at least 1 participant with an AE, if the true incidence rate of the AE is 5%; if the 
true incidence rate is 10%, then the probability to observe it will be approximately 99%. 
Phase 2 Northern Hemisphere 
Approximately 500 participants will be randomly assigned in a 3:3:3:1 ratio to the mRNA-1010 
25, 50, 100 µg groups, or the Active Comparator Group. A total of 450 participants will receive 
the mRNA-1010 vaccine (150 participants at each dose level). A sample size of 150 participants 
at each dose level has at least a 95% probability to observe at least 1 participant with an AE, if the 
true incidence rate is 2%; if the true incidence rate is 3%, then the probably to observe it will be 
99%. 
Phase 2 Extension 
Approximately 200 participants will be randomly assigned in a 1:1:1:1 ratio to the mRNA-1010 
6.25, 12.5, 25 µg groups, or the Active Comparator Group. A total of 150 participants will receive 
the mRNA-1010 vaccine (50 participants at each dose level). With 50 participants receiving an 
investigational vaccine, there is a probability of approximately 92% to observe at least 1 participant 
with an AE, if the true incidence rate of the AE is 5%; if the true incidence rate is 10%, then the 
probability to observe it will be approximately 99%.  

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9.4. 
Analysis Sets 
The analysis sets are described in Table 14. 
Table 14 Analysis Sets 
Set 
Description 
Randomization Set 
The Randomization Set consists of all participants who are 
randomly assigned. 
Full Analysis Set (FAS)1 
The FAS consists of all randomly assigned participants who 
receive the IP. 
Per-Protocol (PP) Set2 
The PP Set consists of all participants in the FAS who comply 
with the injection schedule, comply with the timings of 
immunogenicity blood sampling to have a baseline and at least 
1 postinjection assessment, do not have influenza infection at 
baseline through Day 29 (as documented by PCR testing), and 
have no major protocol deviations that impact the immune 
response. 
Safety Set3 
The Safety Set consists of all randomly assigned participants 
who receive the IP. 
Solicited Safety Set4 
The Solicited Safety Set consists of all participants in the Safety 
Set who contribute any solicited AR data. 
Abbreviations: AR = adverse reaction; IP = investigational product; PCR = polymerase chain reaction; RT-PCR = reverse 
transcription polymerase chain reaction. 
1. 
For the FAS, participants will be analyzed according to the group to which they were randomized. 
2. 
The PP Set will be used as the primary analysis set for analyses of immunogenicity unless otherwise specified. Participants 
will be analyzed according to the group to which they were randomized. 
3. 
The Safety Set will be used for all analyses of safety, except for the solicited ARs. Participants will be included in the 
vaccination group corresponding to what that they actually received. 
4. 
The Solicited Safety Set will be used for the analyses of solicited ARs and participants will be included in the vaccination 
group corresponding to what that they actually received. 
9.5. 
Statistical Methods 
All analyses and data summaries/displays will be provided by vaccination group and overall. 
9.5.1. 
Baseline Characteristics and Demographics 
Demographic variables (eg, age, gender, race, ethnicity, height, weight, and BMI) and baseline 
characteristics will be summarized by vaccination group and overall. Summary statistics (mean 
and standard deviation for continuous variables, and number and percentage for categorical 
variables) will be provided. 
9.5.2. 
Safety Analyses 
All safety analyses will be based on the Safety Set, except summaries of solicited ARs, which will 
be based on the Solicited Safety Set. All safety analyses will be provided by vaccination group. 

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Participants will be included in the vaccination group corresponding to what 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 (including any clinical safety laboratory 
abnormalities [Phase 1/2 part only]), treatment-related AEs, severe AEs, SAEs, AESIs, MAAEs, 
AEs leading to withdrawal from study participation, vital sign measurements, and physical 
examination findings. 
The number and percentage of participants with any solicited local AR, solicited systemic AR, and 
solicited AR during the 7-day follow-up period after the injection will be summarized. A 2-sided 
95% exact confidence interval (CI) using the Clopper-Pearson method will also be provided for 
the percentage of participants with any solicited AR. 
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 coded according to the MedDRA for AR terminology and 
presented by MedDRA system organ class and preferred term. 
Solicited ARs will be coded according to the MedDRA for AR terminology. The toxicity grading 
scale for healthy adult and adolescent volunteers enrolled in preventive vaccine clinical trials will 
be used in this study with modification for rash, solicited ARs, and vital signs (DHHS 2007b). 
Unsolicited AEs will be presented by MedDRA system organ class and preferred term. 
The number of events of unsolicited AEs/SAEs, AESIs, and MAAEs will be reported in summary 
tables accordingly. For all other safety parameters, descriptive summary statistics will be provided. 
Assessment of safety laboratory tests will be done for the Phase 1/2 part of the study only. The 
number and percentage of participants who have chemistry and hematology results below or above 
the normal laboratory ranges will be tabulated by time point. For treatment-emergent safety 
laboratory test results, the raw values and change from baseline values will be summarized by 
vaccination group and visit at each time point. 
For all parts of the study, vital sign results will be presented. 
Table 15 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 15 Analysis Strategy for Safety Parameters 
Safety Endpoint 
Number and Percentage of 
Participants, Number of Events 
95% CI 
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. 
Note: 95% CI using the Clopper-Pearson method. X = results will be provided. 
9.5.3. 
Immunogenicity Analyses 
Immunogenicity analyses in each part of the study will be reported based on the PP Set and 
provided by vaccination group, unless otherwise specified. 
Phase 1/2 
For the immunogenicity endpoints, geometric mean of specific antibody titers with corresponding 
95% CI at each time point and geometric mean fold rise (GMFR) of specific antibody titers with 
corresponding 95% CI at each postbaseline time point over preinjection baseline at Day 1 will be 
provided by vaccination group. The 95% CIs will be calculated based on the t-distribution of the 
log 2-transformed values and then back transformed to the original scale. Descriptive summary 
statistics, including median, minimum, and maximum, will also be provided. 
For calculation of geometric mean titers (GMTs), antibody titers reported as below the lower limit 
of quantification (LLOQ) will be replaced by 0.5 × LLOQ. Values that are greater than the upper 
limit of quantification (ULOQ) will be converted to the ULOQ. 
Seroconversion rate from baseline will be provided with a 2-sided 95% CI using the 
Clopper-Pearson method at each postbaseline time point. Rate of seroconversion is defined as the 
proportion of participants with either a prevaccination HAI titer < 1:10 and a postvaccination HAI 
titer ≥ 1:40 or a prevaccination HAI titer ≥ 1:10 and a minimum 4-fold rise in postvaccination HAI 
antibody titer. 

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Further details will be described in the SAP. 
Phase 2 Northern Hemisphere 
Immune responses, as measured by GMT and seroconversion rate in the mRNA-1010 groups 
based on Day 29 HAI titers, will be compared with that of participants receiving active comparator 
for all 4 strains. 
An analysis of covariance model will be carried out with HAI titers at Day 29 as a dependent 
variable and a group variable as the fixed variable. The GMT of the mRNA-1010 at Day 29 will 
be estimated by the geometric least square mean (GLSM) from the model. The geometric mean 
ratio (GMTr; ratio of GMT) will be estimated by the ratio of GLSM from the model. The 
corresponding 2-sided 95% CI will be provided to assess the difference in immune response 
between the mRNA-1010 compared with the active comparator at Day 29. 
The number and percentage of participants with seroconversion due to vaccination will 
be provided with 2-sided 95% CI using the Clopper-Pearson method at Day 29. The 
seroconversion rate difference with 95% CI at Day 29 will be provided. 
In addition, the GMT of HAI titers with corresponding 95% CI will be provided at each time point. 
The 95% CIs will be calculated based on the t-distribution of the log-transformed values and then 
back transformed to the original scale. The GMFR of HAI titers with corresponding 95% CI at 
each postbaseline time point over baseline will be provided. Descriptive summary statistics, 
including median, minimum, and maximum, will also be provided. 
For summarizations of GMTs, antibody titers reported as LLOQ will be replaced by 0.5 × LLOQ. 
Values that are greater than ULOQ will be converted to the ULOQ. 
Rate of seroconversion is defined as (1) if LLOQ is 1:10, the proportion of participants with either 
a prevaccination HAI titer < 1:10 and a postvaccination HAI titer ≥ 1:40 or a prevaccination HAI 
titer ≥ 1:10 and a minimum 4-fold rise in the postvaccination HAI antibody titer; or (2) if LLOQ 
is greater than 1:10, the proportion of participants with either a prevaccination HAI titer < LLOQ 
and a postvaccination HAI ≥ 4 times of LLOQ, or a prevaccination HAI ≥ LLOQ and a minimum 
4-fold rise in the postvaccination HAI . 
The HAI titers at Day 29, GMTr at Day 29, and the difference in seroconversion rate at Day 29 
may also be performed with the Full Analysis Set as supplementary analyses. 
Phase 2 Extension 
Immune responses, as measured by GMT and seroconversion rate in the mRNA-1010 groups 
based on Day 29 HAI titers, will be compared with that of participants receiving active comparator 
for all 4 strains. 

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The number and percentage of participants with seroconversion due to vaccination will 
be provided with 2-sided 95% CI using the Clopper-Pearson method at Day 29. The 
seroconversion rate difference with 95% CI at Day 29 will be provided. 
For summarizations of GMTs, antibody titers reported as LLOQ will be replaced by 0.5 × LLOQ. 
Values that are greater than ULOQ will be converted to the ULOQ. The definition of rate of 
seroconversion will be the same definition as the rate of seroconversion in Phase 2 NH. 
9.5.4. 
Exploratory Analyses 
Exploratory analyses not addressed in Section 9.5.3 will be described in the SAP before database 
lock. 
9.5.5. 
Subgroup Analyses 
The protocol does not define any formal subgroup analyses, and the study is not adequately 
powered to perform subgroup analyses. 
9.6. 
Study Analyses 
A Day 29 IA is planned in this study for the Phase 1/2, Phase 2 NH, and Phase 2 Extension parts 
separately. The IA for the Phase 1/2 part will be performed after all participants have completed 
the Day 29 Visit. All relevant data to the IA will be cleaned (ie, data that are as clean as possible). 
For the Phase 2 NH and Phase 2 Extension parts, an IA of safety (reactogenicity and 
immunogenicity as applicable) will be performed after participants have completed the Day 29 
Visit for each part of the study. All data relevant to the IA through the Day 29 Visit will be cleaned 
(ie, data that are as clean as possible). An interim study report may be generated, in which case a 
formal database lock will be performed to support the interim study report. 
The IA will be performed by a separate team of unblinded programmers and statisticians. The 
analysis will be presented by vaccination groups. Except for a limited number of Sponsor and CRO 
personnel who will be unblinded to perform the IA, the study site staff, Investigators, study 
monitors, and participants will remain blinded until after the final database lock for final analysis. 
The final analysis of safety, reactogenicity, and immunogenicity will be performed after all 
participants have completed all planned study procedures. The results of this analysis will be 
presented in a final CSR, including individual listings. 
Further details can be found in the SAP. 

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10. 
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the licensure of seasonal inactivated influenza vaccines. May 2007a [cited 2021 Mar 18] 
[17 screens]. Available from: 
https://www.fda.gov/files/vaccines%2C%20blood%20%26%20biologics/published/Guidance-
for-Industry--Clinical-Data-Needed-to-Support-the-Licensure-of-Seasonal-Inactivated-Influenza-
Vaccines.pdf. 
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 2007b 
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https://www.fda.gov/downloads/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInfor
mation/Guidances/Vaccines/ucm091977.pdf. 
Department of Health and Human Services (DHHS), Food and Drug Administration (US). 
Guidance for industry, investigators, and institutional review boards: Conduct of clinical trials of 
medical products during the COVID-19 public health emergency. March 2020 [updated 
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Dunning AJ, DiazGranados CA, Voloshen T, Hu B, Landolfi VA, Talbot HK. Correlates of 
protection against influenza in the elderly: results from an influenza vaccine efficacy trial. Clin 
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clinical-module_en.pdf. 
Feldman RA, Fuhr R, Smolenov I, Ribeiro AM, Panther L, Watson M, et al. mRNA vaccines 
against H10N8 and H7N9 influenza viruses of pandemic potential are immunogenic and well 
tolerated in healthy adults in phase 1 randomized clinical trials. Vaccine. 2019;37(25):3326-34. 
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;70(27):977-82. 
Jackson LA, Anderson EJ, Rouphael NG, Roberts PC, Makhene M, Coler RN, et al; mRNA-1273 
Study Group. An mRNA vaccine against SARS-CoV-2 – preliminary report. N Engl J Med. 
2020;383(20):1920-31. 
Monto AS. Reflections on the Global Influenza Surveillance and Response System (GISRS) at 
65 years: an expanding framework for influenza detection, prevention, and control. Influenza 
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Trial Group. Safety and efficacy of the BNT162b2 mRNA COVID-19 vaccine. N Engl J Med 
2020;383(27):2603-15. 
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Adelberg’s Medical Microbiology. 28th ed. New York: McGraw-Hill Education; 2019. 
Chapter 39, Orthomyxoviruses (Influenza Viruses); p. 581-94. 
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Microorganisms. 2020;8(11):1745. 
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World Health Organization (WHO). Influenza (seasonal): Ask the expert: influenza Q&A 
[Internet]. 2018 Nov 6 (cited 2021 Mar 17. Available from: https://www.who.int/news-room/fact-
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post-marketing surveillance review. Eur J Pediatr. 2002;161(1):21-5. 

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11. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 

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11.1. 
APPENDIX 1: Study Governance Considerations 
11.1.1. 
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 GCP guidelines, the IRB, and all other applicable 
local regulations. 
11.1.2. 
Study Monitoring 
Before an investigational study site can enter a participant into the study, the Sponsor or its 
representatives will visit the study site for the following: 
• 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 guidelines, 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 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 study site, for 
the following purposes: 
• 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 that AEs and SAEs have been properly documented on eCRFs, that any 
SAEs have been forwarded to the SAE Hotline, and that those SAEs that meet 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. 
11.1.3. 
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 study 
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 whether 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 ICF and recruitment 
materials must be maintained by the Investigator and made available for inspection. 
11.1.4. 
Financial Disclosure 
The Investigator is required to provide financial disclosure information to allow the Sponsor to 
submit the complete and accurate certification or disclosure statements required under 
21 CFR 54. In addition, the Investigator must provide the Sponsor with a commitment to 
promptly update this information if any relevant changes occur during the course of the 
investigation and for 1 year following the completion of the study. 
The Sponsor, the CRO, and the study site are not financially responsible for further testing or 
treatment of any medical condition that may be detected during the screening process. In addition, 
in the absence of specific arrangements, the Sponsor, the CRO, and the study site are not 
financially responsible for further treatment of the disease under study. 
11.1.5. 
Recruitment Procedures 
Advertisements to be used for the recruitment of study participants and any other written 
information regarding this study to be provided to the participant should be submitted to the 
Sponsor for approval. All documents must be approved by the IRB. 
11.1.6. 
Informed Consent Process 
The informed consent document(s) must meet the requirements of 21 CFR 50, local regulations, 
ICH guidelines, Health Insurance Portability and Accountability Act requirements, where 
applicable, and the IRB or study site. All consent documents will be approved by the appropriate 
IRB. The actual ICF used at each study site may differ, depending on local regulations and IRB 
requirements. However, all versions must contain the standard information found in the sample 

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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. 
If new information becomes available that may be relevant to the participant’s willingness to 
continue participation in the study, this will be communicated to him/her in a timely manner. Such 
information will be provided via a revised ICF or an addendum to the original ICF. 
The Investigator or his/her representative will explain the nature of the study to the participant and 
answer all questions regarding the study. 
The Investigator is responsible for ensuring that the participant fully understands the nature and 
purpose of the study. Information should be given in both oral and written form whenever possible. 
No participant should be obliged to participate in the study. The participant must be informed that 
participation is voluntary. Participants, their relatives, guardians, or (if applicable) legal 
representatives must be given ample opportunity to inquire about details of the study. The 
information must make clear that refusal to participate in the study or withdrawal from the study 
at any stage is without any prejudice to the participant’s subsequent care. 
The participant must be allowed sufficient time to decide whether they wish to participate. 
The participant must be made aware of and give consent to direct access to his/her source medical 
records by study monitors, auditors, the IRB, 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 influenza viruses, for additional assay development, and to examine the 
immune response across influenza viruses. 
11.1.7. 
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. 
The IRB 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 that 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 and agreed to by the Investigators, and the IRB(s) will be notified. 
11.1.8. 
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 in a timely manner. 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. 
11.1.9. 
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 that 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 (QA) 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 HCP 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. 
11.1.10. 
Sample Retention and Future Biomedical Research 
The Sponsor may store laboratory samples for the time frame specified in the ICF to address study 
objectives or further scientific questions related to mRNA-1010 or anti-respiratory viral immune 
response. In addition, identifiable samples can be destroyed at any time at the request of the 
participant. During the study or during the retention period, in addition to the analysis outlined in 
the study endpoints, exploratory analysis may be conducted using other measures of adaptive 
immunity to seasonal influenza 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. In the Phase 2 NH and Phase 2 Extension parts of the study, these 
analyses will extend the search for other potentially relevant biomarkers to investigate the effect 
of mRNA-1010 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 vaccine class, as well as reagents for biomarker assay development. 
11.1.11. 
Safety Oversight 
Safety monitoring for this study will include the blinded study team members, inclusive of, at a 
minimum, the Sponsor’s medical monitor, CRO’s medical monitor, a blinded IST, and an 
unblinded DSMB. The study team will conduct ongoing blinded safety reviews during the study 
and will be responsible for notifying the IST and DSMB of potential safety signal events or the 
triggering of pause rules. 
The IST will consist of at least 2 Sponsor physicians who will be voting members not directly 
involved in the clinical development of the study. For the initial stage in the Phase 1/2 part of the 
study, the IST will conduct a blinded review of all available safety data after at least 36 participants 

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(9 participants per vaccination group; Table 6) have completed their Day 8 Visit. Vaccination of 
the remaining participants in the expansion stage will continue in each vaccination group if no 
pause rules have been met and the safety and tolerability are acceptable. Prior to the start of the 
Phase 2 NH part of the study, the IST will also conduct a blinded review of available safety data 
from the Phase 1/2 part of the study. Finally, the IST will also conduct ad hoc reviews as requested 
by the study medical monitor and the study team. 
An independent unblinded DSMB will be used throughout the conduct of this study. This 
committee will be composed of independent members with relevant therapeutic and/or 
biostatistical expertise to allow for the ongoing unblinded review of safety data from this study 
population. Safety data will be reviewed according to intervals defined in the DSMB charter and 
will also occur as needed when study stopping or pausing criteria are met, or as otherwise requested 
by the study team and/or IST. 
Details regarding the IST and DSMB composition, responsibilities, procedures, and frequency of 
data review will be defined in their respective charters. 
11.1.12. 
Dissemination of Clinical Study Data 
The Sponsor shares information about clinical studies and results on publicly accessible websites, 
based on international and local legal and regulatory requirements, and other clinical study 
disclosure commitments established by pharmaceutical industry associations. These websites 
include clinicaltrials.gov, European Union clinical trial register (eu.ctr), and some national 
registries. 
11.1.13. 
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. 

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• 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). 
• 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 QA representative from the Sponsor or qualified designee, who is independent of and separated 
from routine monitoring, may periodically arrange inspections/audits of the clinical study by 
reviewing the data obtained and procedural aspects. These inspections may include onsite 
inspections/audits and source data checks. Direct access to source documents is required for the 
purpose of these periodic inspections/audits. 
11.1.14. 
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. 

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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 
WHODrug Global. 
11.1.15. 
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. Also, current medical records must 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, 
study site, or office charts and the signed ICFs are to be included in the Investigator’s files with 
the participant’s study records. 
11.1.16. 
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. 

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11.1.17. 
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 ensure appropriate participant 
therapy and/or follow-up. 
The Sponsor or designee reserves the right to close the study site or terminate the study at any time 
for any reason at the sole discretion of the Sponsor. 
The Investigator may initiate study site closure at any time, provided there is reasonable cause and 
sufficient notice is given in advance of the intended termination. 
Reasons for the early closure of a study site by the Sponsor or Investigator may include but are not 
limited to the following: 
• 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 ICH GCP guidelines. 
• Inadequate recruitment of participants by the Investigator. 
• Discontinuation of further mRNA-1010 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. 
11.1.18. 
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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11.2. 
APPENDIX 2: Contraceptive Guidance 
Definitions: Woman of Childbearing Potential 
Females of childbearing potential are those who are considered fertile following menarche and 
until becoming postmenopausal unless permanently sterile (as follows). If fertility is unclear (eg, 
amenorrhea in adolescents or athletes) and a menstrual cycle cannot be confirmed before study 
vaccination, additional evaluation should be considered. 
Females in the following categories are not considered females 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’s discretion should be 
applied when 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: 
− Females < 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. 
− Females ≥ 50 years of age would be considered postmenopausal if they have been 
amenorrheic for 12 months or more, had radiation-induced menopause with last 
menses > 1 year ago, or had chemotherapy-induced menopause with last menses 
> 1 year ago. 
• A high FSH level in the postmenopausal range may be used to confirm a 
postmenopausal state in women not using hormone replacement therapy (HRT). 
• Females on HRT and whose menopausal status is in doubt will be required to use 1 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. The following are examples: 
• 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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11.3. 
APPENDIX 3: Adverse Events of Special Interest Terms 
Investigators should report all AEs, which fall into the following categories presented in Table 16 
as an AESI per the reporting processes specified in Section 8.4.14. The following AESIs are 
medical concepts that are generally of interest in vaccine safety surveillance per the Brighton 
Collaboration and Safety Platform for Emergency Vaccines. 
Table 16 Adverse Events of Special Interest 
Adverse Event of Special Interest 
Notes 
Thrombocytopenia 
• 
Platelet counts < 150 × 109 
• 
Including but not limited to immune thrombocytopenia, 
platelet production decreased, thrombocytopenia, 
thrombocytopenic purpura, thrombotic thrombocytopenic 
purpura, or HELLP syndrome 
New onset of or worsening of the 
following neurologic diseases 
• 
Guillain-Barre Syndrome 
• 
Acute disseminated encephalomyelitis 
• 
Idiopathic peripheral facial nerve palsy (Bell’s palsy) 
• 
Seizures including, but not limited to, febrile seizures 
and/or generalized seizures/convulsions 
Anaphylaxis  
• 
Anaphylaxis as defined in Section 8.4.5 
• 
Following reporting procedures as specified in 
Section 8.4.14 
Myocarditis/Pericarditis 
• 
Myocarditis 
• 
Pericarditis 
• 
Myopericarditis 
Abbreviation: HELLP = hemolysis, elevated liver enzymes, low platelet count. 
 
 
 

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11.4. 
APPENDIX 4: CDC Working Case Definition of Pericarditis, 
Myocarditis, and Myopericarditis Occurring After Receipt of 
COVID-19 mRNA Vaccines 
Table 17 Case Definitions of Probable and Confirmed Myocarditis, Pericarditis, and 
Myopericarditis 
Condition 
Definition 
Acute myocarditis 
Probable case 
Confirmed Case 
Presence of ≥ 1 new or worsening of 
the following clinical symptoms:* 
Presence of ≥ 1 new or worsening of 
the following clinical symptoms:* 
• 
chest pain, pressure, or 
discomfort 
• 
chest pain, pressure, or 
discomfort 
• 
dyspnea, shortness of breath, 
or pain with breathing 
• 
dyspnea, shortness of breath, 
or pain with breathing 
• 
palpitations 
• 
palpitations 
• 
syncope 
• 
syncope 
OR, infants and children aged 
< 12 years might instead have ≥ 2 of 
the following symptoms: 
OR, infants and children aged 
< 12 years might instead have ≥ 2 of 
the following symptoms: 
• 
irritability 
• 
irritability 
• 
vomiting 
• 
vomiting 
• 
poor feeding 
• 
poor feeding 
• 
tachypnea 
• 
tachypnea 
• 
lethargy 
• 
lethargy 
AND 
AND 
≥ 1 new finding of 
≥ 1 new finding of 
• 
troponin level above upper 
limit of normal (any type of 
troponin) 
• 
Histopathologic confirmation 
of myocarditis† 
• 
abnormal electrocardiogram 
(ECG or EKG) or rhythm 
monitoring findings 
consistent with myocarditis§ 
• 
abnormal cardiac function or 
wall motion abnormalities on 
echocardiogram 
• 
cMRI findings consistent 
with myocarditis in the 
presence of troponin level 
above upper limit of normal 
(any type of troponin) 
• 
cMRI findings consistent 
with myocarditis 
AND 
AND 
• 
No other identifiable cause of 
the symptoms and findings 
• 
No other identifiable cause of 
the symptoms and findings 

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Condition 
Definition 
Acute pericarditis** 
Presence of ≥ 2 new or worsening of the following clinical features: 
• 
acute chest pain†† 
• 
pericardial rub on exam 
• 
new ST-elevation or PR-depression on EKG 
• 
new or worsening pericardial effusion on echocardiogram or MRI 
Myopericarditis 
This term may be used for patients who meet criteria for both myocarditis and 
pericarditis. 
Abbreviations: AV = atrioventricular; cMRI = cardiac magnetic resonance imaging; ECG or EKG = electrocardiogram; 
MRI = magnetic resonance imaging. 
Note: An independent Cardiac Event Adjudication Committee (CEAC) comprised of medically qualified personnel, including 
cardiologists, will review suspected cases of myocarditis, pericarditis, and myopericarditis to determine if they meet Center for 
Disease Control and Prevention criteria for “probable” or “confirmed” events, (Gargano et al 2021), and provide the assessment 
to the Sponsor. The CEAC members will be blinded to study treatment. Details regarding the CEAC composition, 
responsibilities, procedures, and frequency of data review will be defined in the CEAC charter. 
* Persons who lack the listed symptoms but who meet other criteria may be classified as subclinical myocarditis (probable or 
confirmed). 
† Using the Dallas criteria (Aretz et al 1987). Autopsy cases may be classified as confirmed clinical myocarditis on the basis of 
meeting histopathologic criteria if no other identifiable cause. 
§ To meet the ECG or rhythm monitoring criterion, a probable case must include at least one of 1) ST-segment or T-wave 
abnormalities; 2) Paroxysmal or sustained atrial, supraventricular, or ventricular arrhythmias; or 3) AV nodal conduction delays 
or intraventricular conduction defects. 
Using either the original or the revised Lake Louise criteria. 
https://www.sciencedirect.com/science/article/pii/S0735109718388430?via%3Dihubexternal icon 
** https://academic.oup.com/eurheartj/article/36/42/2921/2293375external icon 
†† 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 might occur. 
Reference: (Gargano et al 2021). 
 
 

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11.5. 
APPENDIX 5: Protocol Amendment History 
The document history table for this protocol and the Protocol Amendment Summary of Changes 
table for the current Amendment 4 is located directly before Section 1. 
Description of Amendments 1, 2, and 3 are presented in this appendix. 
Amendment 1, 22 Jul 2021 
Main Rationale for the Amendment: 
The main purpose of this amendment is to incorporate a new part (Phase 2 Northern Hemisphere 
[NH]) into the study. By incorporating the Phase 2 NH part, the study intends to increase the size 
of the safety database for each dose level of the mRNA-1010 vaccine tested in the originally 
planned (ie, Phase 1/2 part) study. In addition, the Phase 2 NH part of the study will include a 
composition change of mRNA-1010 (strain update for the 2021-2022 NH season), as well as the 
inclusion of a licensed active comparator. 
The summary of changes table provided here describes the major changes made in Amendment 1 
relative to the original protocol, including the sections modified and the corresponding rationales. 
As applicable, the synopsis of Amendment 1 has been modified to correspond to changes in the 
body of the protocol. 
Summary of Major Changes From Original Protocol to Protocol Amendment 1: 
Section # and Name 
Description of Change 
Brief Rationale 
Section 1.2 (Schema) and 
Section 1.3 (Schedule of 
Events) 
• In the SoE for the Phase 1/2 part, the 
row specifying the assessment 
“Recording of SAEs and concomitant 
medications relevant to or for the 
treatment of the SAE” has been 
updated to include AESIs. 
• In the SoE for the Phase 1/2 part, the 
row specifying “study completion” 
has been updated to change the 
wording to “Phase 1/2 completion” in 
line with the nomenclature used to 
identify the 2 study parts. 
• Added an instruction in footnote 4 
regarding vital sign measurements in 
the Phase 1/2 part SoE that the 
participants will be seated for at least 
5 minutes before all measurements are 
taken. 
• AESIs have been added to the 
Phase 1/2 part SoE as 1 of the 
safety assessments to be 
performed. 
• In the Phase 1/2 part SoE, added 
an instruction in footnote 4 for 
vital sign measurements to take 
measurements only after the 
participants have been rested in a 
seating position for at least 
5 minutes; number of 
participants in footnote 7 
regarding assessment of cellular 
immunogenicity samples has 
been updated; and added 
clarification in footnote 8 for NP 
swab collection that the NP swab 
samples may be collected at 
home if needed in lieu of a study 
site visit. 

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Section # and Name 
Description of Change 
Brief Rationale 
• In the Phase 1/2 part SoE, footnote 7 
has been updated to specify that 
cellular immunogenicity samples will 
be collected from approximately 
40 participants per vaccination group 
instead of 25 participants per 
vaccination group as stated in the 
original protocol. 
• Added in footnote 8 regarding NP 
swab specimen in the Phase 1/2 part 
that the swabs may be collected as 
part of a home visit in lieu of a study 
site visit. 
• Added study design for the Phase 2 
NH part. Added SoE planned for the 
Phase 2 NH part. 
• To provide the time points for 
the evaluation of assessments 
planned for the Phase 2 NH part. 
Section 2.2.1 (mRNA-1010), 
Section 2.3.1 (Known 
Potential Benefits), and 
Section 2.3.3 (Overall 
Benefit/Risk Conclusion) 
• Text has been updated to include 
information on the Phase 2 NH part of 
the study. 
• Addition of a Phase 2 NH part to 
the originally planned study does 
not affect the potential benefits 
or risks associated with study 
participation for participants.  
Section 3 (Objectives and 
Endpoints) 
• New section (Section 3.2: Phase 2 
NH) has been created to provide the 
objectives and endpoints of the newly 
added Phase 2 NH part of the study. 
• The following exploratory objective 
for the Phase 1/2 part of the study “To 
assess the occurrence of clinical 
influenza in study participants and 
characterize their immune response to 
infection and viral isolates” has been 
revised to “To assess the occurrence 
of ILI in study participants and 
characterize their immune response to 
infection and viral isolates.” 
Corresponding endpoint description 
has also been updated wherein 
laboratory-confirmed clinical 
influenza was updated to 
“RT-PCR-confirmed ILI.” 
• The primary safety endpoint of 
reporting of any SAEs and MAAEs 
from Day 1 through Day 181/EoS for 
the Phase 1/2 part has been updated to 
include AESIs as well. 
• Provided the objectives and 
endpoints of the Phase 2 NH part 
of the study. 
• Included recording of AESIs 
from Day 1 through 
Day 181/EoS in the primary 
safety endpoint for the Phase 1/2 
part. 

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Section # and Name 
Description of Change 
Brief Rationale 
• Section 3 now includes 2 subsections 
to separate objectives for the 2 study 
parts (Phase 1/2 and Phase 2 NH). 
• The originally planned objectives and 
endpoints (for the Phase 1/2 part) are 
now tabulated under Section 3.1 
(Phase 1/2). 
Section 4.1 (General Design) 
and Section 4.2 (Scientific 
Rationale for Study Design) 
• Added design, duration, 
randomization, vaccination groups, 
and dosing, assessment procedures for 
the Phase 2 NH part of the study. 
• The age group “18 to 49 years” used 
as a stratification factor for 
randomization in the expansion stage 
of the Phase 1/2 part has been updated 
to “18 to < 50 years.” 
• Provided information on the 
specific procedures for the 
Phase 2 NH part of the study. 
• Provided rationale for the 
general design elements of the 
Phase 2 NH part of the study. 
• Updated the age stratification 
randomization factor for the 
expansion stage in the Phase 1/2 
part of the study. 
Section 4.3 (End of Study 
Definition) 
• EoS definition has been updated to 
“The study will be considered ended 
at the completion of the last visit of 
the last participant in the Phase 2 NH 
part of the study or the last scheduled 
procedure as shown in the SoE 
(Table 2) for the last participant in the 
Phase 2 NH part of the study.” 
• Addition of the Phase 2 NH part 
resulted in updating the EoS 
definition as the study can be 
considered ended (ie, complete) 
only when the last participant’s 
last visit in the Phase 2 NH part 
is completed. 
Section 5 (Study Population) 
• Added inclusion and exclusion criteria 
for the Phase 2 NH part in 
Section 5.2.1 and Section 5.2.2, 
respectively. 
• Section 5 now includes 4 subsections 
to separate the inclusion/exclusion 
criteria for each part (Phase 1/2 and 
Phase 2 NH). The inclusion/exclusion 
criteria for the Phase 1/2 part are now 
listed in Section 5.1.1 and 
Section 5.1.2, respectively. 
• Exclusion criterion No. 5 for the 
Phase 1/2 part has been updated to 
clarify that the participants may be 
rescreened if they are not medically 
stable at the Screening Visit. 
• Provided a list of the inclusion 
and exclusion criteria for 
participant eligibility for Phase 2 
NH part. 
• Specified the allowance for 
rescreening of participants in the 
Phase 1/2 part for those who are 
not medically stable at screening. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 5.3 (Lifestyle 
Restrictions) 
• Text has been updated to clarify that 
only when participants choose to 
receive an available seasonal 
influenza vaccine, will they be 
requested to defer that vaccination 
while in the study.  
• To clarify when participants will 
be requested to defer receiving 
commercially available seasonal 
influenza vaccination 
administered outside the study if 
they choose to receive it.  
Section 6.1 (Investigational 
Products Administered), 
Section 6.2 (Randomization), 
Section 6.3 
(Preparation/Handling/Storage/ 
Accountability) and 
subsections 
• Text has been updated to include 
information on the IPs administered in 
the Phase 2 NH part of the study. 
• The age group “18 to 49 years” used 
as a stratification factor for 
randomization in the expansion stage 
of the Phase 1/2 part has been updated 
to “18 to < 50 years.” 
• Name of the “mRNA-1010 Pharmacy 
Manual” has been updated to 
“Pharmacy Manual.” 
• Provided information on the IPs 
administered in the Phase 2 NH 
part and related instructions on 
storage, handling, preparation, 
processing, and accountability of 
the products administered. 
• Updated the age stratification 
randomization factor for the 
expansion stage in the Phase 1/2 
part of the study. 
• Name of the Pharmacy Manual 
has been updated because of the 
restrictive wording. The manual 
will include information on the 
active comparator to be 
administered in the Phase 2 NH 
part in addition to the originally 
added details on mRNA-1010. 
Section 6.5.2 (Concomitant 
Medications and Therapies) 
• Revised language for 1 of the 
concomitant medications/therapies 
information criterion to specify that 
information of any seasonal influenza 
vaccine administered since 
September 2020 will be collected 
from participants and added in the 
eCRF. 
• Added that the study staff should also 
ask the participants whether they have 
received any authorized or 
investigational COVID-19 vaccine at 
any time before the IP injection. If 
yes, the information should be 
recorded in the eCRF. 
• Clarified text to avoid ambiguity 
regarding collection of previous 
seasonal influenza vaccine(s) 
received by the participants. 
• Added a new data collection 
criterion regarding 
concomitant/prior medications 
received by the participant. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 7.1 (Pause Rules) 
• New section (Section 7.1.2: Pause 
Rules for the Phase 2 NH Part of the 
Study) has been created to provide the 
study pause rules of the newly added 
Phase 2 NH part of the study. 
• Footnote b in Table 9 (Phase 1/2 
Pause Rule Criteria, Events, and 
Thresholds - Proportion of 
Participants) was updated to include 
the following text: The calculation for 
≥ 20% of participants in the expansion 
stage includes participants in the 
initial stage and the expansion stage as 
the total number of participants in the 
denominator. 
• Section 7.1 now includes 2 main 
subsections to separate pause rules for 
the 2 study parts (Phase 1/2 
[Section 7.1.1] and Phase 2 NH 
[Section 7.1.2]). 
• Included explicit criteria as to 
when the Phase 2 NH part of the 
study should be paused. 
• Footnote b in Phase 1/2 Pause 
Rule Criteria, Events, and 
Thresholds - Proportion of 
Participants) was updated to 
clarify text regarding calculation 
of proportion of participants for 
pause rule implementation if 
needed for the Phase 1/2 part. 
Section 7.2 (Criteria for Delay 
or Withholding of Study 
Vaccination) 
• The timing of receipt of COVID-19 
vaccination before the planned Day 1 
study vaccination that constitutes a 
delay in the receipt of study 
vaccination has been updated from 
“within 14 days” to “within 7 to 
14 days.” 
• Updated the criterion pertaining 
to the receipt of COVID-19 
vaccination that constitute a 
delay or withholding of study 
vaccination. 
Section 8.1 (Safety 
Assessments and Procedures), 
Section 8.1.1 (Use of 
Electronic Diaries), 
Section 8.1.3 (Safety 
Laboratory Assessments), 
Section 8.1.4 (Vital Sign 
Measurements), Section 8.1.5 
(Physical Examination), 
Section 8.1.6 (Assessments for 
Respiratory Viral Infections), 
Section 8.2 (Immunogenicity 
Assessments), and Section 8.3 
(Efficacy Assessments) 
• Text has been updated to include 
safety, immunogenicity, and efficacy 
assessments and procedures to be 
performed for Phase 2 NH part of the 
study. 
• Clarified that the safety laboratory 
assessments will be performed only in 
the Phase 1/2 part of the study. 
• Efficacy assessments as exploratory 
endpoints have been described in 
more detail. 
• Provided text on the assessments 
and procedures planned for the 
Phase 2 NH part of the study. 
Section 8.2 (Immunogenicity 
Assessments) 
• Total maximum blood volume 
collected from the participant during 
his/her study participation has been 
updated from “250 mL” to “450 mL.” 
• Total maximum blood volume to 
be collected from a participant in 
the study has been updated. 

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Section # and Name 
Description of Change 
Brief Rationale 
Section 8.4.4 (Medically 
Attended Adverse Events) 
• Text has been updated to clarify that 
there will not be a separate MAAE 
section in the eCRF. Any MAAEs 
will be recorded under unsolicited 
AEs in the AE section of the eCRF. 
• Clarified the precise section to 
record MAAEs in the eCRF. 
Section 8.4.5 (Anaphylaxis) 
• A new section has been added by 
incorporating the information about 
anaphylaxis previously added to the 
section of MAAEs (Section 8.4.4). 
• All information related to 
anaphylaxis is now incorporated 
in a new separate section. 
Section 8.4.6 (Influenza-Like 
Illness) 
• Definitions have been added for ILI 
(protocol-defined, CDC-defined, and 
RT-PCR-confirmed). 
• Added definitions for ILI. 
Section 8.4.7 (Adverse Events 
of Special Interest), 
Section 8.4.14 (Reporting of 
Adverse Events of Special 
Interest), and Section 11.3 
(Appendix 3: Adverse Events 
of Special Interest Terms); and 
Throughout the Protocol as 
Applicable for Phase 1/2 Part 
• Added text defining AESIs for this 
protocol, reporting requirements, and 
the event terms to be considered as 
AESIs. 
• AESIs also have been added as a 
safety assessment for the Phase 1/2 
part of the study. Therefore, in 
addition to SAEs and MAAEs, AESIs 
will be collected from Day 1 through 
Day 181/EoS in the Phase 1/2 part. 
• The Sponsor has identified 
AESIs for this protocol, which 
will be assessed from Day 1 
through Day 181/EoS in both 
study parts (Phase 1/2 and 
Phase 2 NH). Text has been 
added to provide information on 
such events. 
Section 8.9 (Biomarkers) 
• Added text to specify that for the 
Phase 2 NH part, biomarker 
assessments are yet to be determined 
and possibly may include genomic 
and transcriptomic studies. 
• Added text to specify that biomarker 
assessments will not be performed for 
the Phase 1/2 part of the study outside 
of the described immunogenicity 
assessments. 
• Added text about biomarker 
assessments to be performed in 
the study. 
Section 9.3 (Sample Size 
Determination) 
• A sample size of 500 participants 
(150 participants in each of the 
3 mRNA-1010 groups and 
50 participants in the Active 
Comparator Group) is planned for the 
Phase 2 NH part and corresponding 
text has been added. 
• Text added to justify the planned 
sample size for Phase 2 NH part 
of the study. 
Section 9.5.2 (Safety 
Analyses) and Section 9.5.3 
(Immunogenicity Analyses) 
• Added analysis methods for safety 
and immunogenicity assessments for 
the Phase 2 NH part. 
• Provided text for the statistical 
methodology of the assessments 
planned for the Phase 2 NH part. 

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Section # and Name 
Description of Change 
Brief Rationale 
• Text for safety analyses has been 
updated to include AESI assessment 
for the Phase 1/2 part as well. 
• Text for safety analyses has been 
updated to include assessment of 
AESIs for the Phase 1/2 part. 
Section 9.6 (Study Analyses) 
• Added text for the planned IA for the 
Phase 2 NH part of the study. 
• For the Phase 2 NH part, an IA 
of safety (and immunogenicity as 
applicable) will be performed 
after participants have completed 
the Day 29 Visit. In addition, an 
interim study report may be 
generated, in which case a 
formal database lock will be 
performed to support the interim 
study report. 
Section 10 (References) 
• Included the CDC reference for the 
exclusion criterion No. 10 applicable 
for the Phase 2 NH part. 
• Added reference related to the 
exclusion criterion for the 
Phase 2 NH part. 
Section 11.1.11 (Safety 
Oversight) and Section 4.1 
(Study Design) 
• Added text for the IST and DSMB 
responsibility for the Phase 2 NH data 
review. 
• Added text to specify that for the 
initial stage in the Phase 1/2 part of 
the study, the IST will conduct a 
blinded review of all available safety 
data after at least 36 participants 
(9 participants per vaccination group) 
have completed their Day 8 Visit. 
• Clarified that vaccination of the 
remaining participants in the 
expansion stage will continue in each 
vaccination group if no pause rules 
have been met and the safety and 
tolerability are acceptable. 
• Added that prior to the start of 
the Phase 2 NH part of the study, 
the IST will also conduct a 
blinded review of available 
safety data from the Phase 1/2 
part of the study. 
• Text added to specify the IST 
review of available safety data 
from the initial stage of the 
Phase 1/2 part of the study. 
Throughout the Protocol 
• Minor formatting and edits were made 
for consistency. 
• Minor formatting and edits were 
made for consistency and clarity. 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; CDC = Centers for Disease Control and Prevention; 
COVID-19 = coronavirus disease 2019; DSMB = Data and Safety Monitoring Board; eCRF = electronic case report form; 
EoS = end of study; IA = interim analysis; ILI = influenza-like illness; IP = investigational product; IST = internal safety team; 
MAAE = medically attended adverse event; NH = Northern Hemisphere; NP = nasopharyngeal swab; RT-PCR = reverse 
transcription polymerase chain reaction; SAE = serious adverse event; SoE = schedule of events. 
 
 

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Amendment 2, 19 Aug 2021 
Main Rationale for the Amendment: 
The purpose of this amendment is to describe the observation of myocarditis/pericarditis following 
COVID-19 mRNA vaccines. 
The summary of changes table provided here describes the major changes made in Amendment 2 
relative to Amendment 1, including the sections modified and the corresponding rationales. As 
applicable, the synopsis of Amendment 2 has been modified to correspond to changes in the body 
of the protocol. 
Summary of Major Changes From Protocol Amendment 1 to Protocol Amendment 2: 
Section # and Name 
Description of Change 
Brief Rationale 
Section 2.3.2 (Risks From 
Study Participation and Their 
Mitigation)  
• Added description of myocarditis and 
pericarditis following COVID-19 
mRNA vaccines. 
• To add information on very rare 
reports of myocarditis and 
pericarditis after vaccination 
with COVID-19 mRNA 
vaccines. 
Section 4.1 (General Design) 
and Section 9.6 (Study 
Analyses) 
• Clarified that the Phase 2 NH part will 
also access reactogenicity. 
• Revised for consistency of 
presentation. 
Section 8.4.3 (Solicited 
Adverse Reactions) 
• Clarified documentation of solicited 
adverse reaction collection. 
• Revised for consistency of 
documentation. 
Section 8.4.7 (Adverse Events 
of Special Interest) 
• Added information on 
myocarditis/pericarditis events. 
• To provide guidance to the 
Investigators regarding reporting 
myocarditis and pericarditis for 
this study population. 
Section 10 (References) 
• Updated reference list. 
• To support the text added to the 
protocol for myocarditis and 
pericarditis. 
Section 11.4.(APPENDIX 4: 
CDC Working Case Definition 
of Pericarditis, Myocarditis, 
and Myopericarditis Occurring 
After Receipt of COVID-19 
mRNA Vaccines) 
• Added CDC case definitions for 
myocarditis and pericarditis. 
• Added description of independent 
CEAC as footnote to the table. 
• To provide guidance to the 
Investigators regarding assessing 
and reporting myocarditis and 
pericarditis for this study 
population. 
• To add mechanism for review of 
suspected cases of myocarditis 
and pericarditis. 
Abbreviations: AESI = adverse event of special interest; CDC = Centers for Disease Control and Prevention; CEAC = Cardiac 
Event Adjudication Committee COVID-19 = coronavirus disease 2019; mRNA = messenger RNA; NH = Northern 
Hemisphere. 

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Amendment 3, 21 Oct 2021 
Main Rationale for the Amendment: 
The purpose of this amendment is to update the Phase 2 NH part of the study to test 3 dose levels 
of mRNA-1010 (25, 50, and 100 µg total mRNA; Vaccination Groups 1 to 3). 
The summary of changes table provided here describes the major changes made in Amendment 3 
relative to Amendment 2, including the sections modified and the corresponding rationales. As 
applicable, the synopsis of Amendment 3 has been modified to correspond to changes in the body 
of the protocol. Minor editorial and/or formatting changes are not provided in this summary table. 
Summary of Major Changes From Protocol Amendment 2 to Protocol Amendment 3: 
Section # and Name 
Description of Change 
Brief Rationale 
Title page: Sponsor Contact 
and Medical Monitor 
• Name and contact info of the person 
responsible updated 
• To indicate the change in 
personnel 
Synopsis: Overall Study 
Design; Section 4.1. (General 
Design); Section 4.3. (Choice 
of Vaccine Dose); Section 6.1. 
(Investigational Products 
Administered); Section 6.2.2. 
(Phase 2 Northern 
Hemisphere); Section 6.3.1. 
(Preparation of Investigational 
Product); Section 9.3. (Sample 
Size Determination) 
• Updated the Phase 2 NH part of the 
study to test 3 dose levels of 
mRNA-1010 (25, 50, and 100 µg total 
mRNA) 
• Based on interim analysis results 
of the Phase 1/2 study, the 
200 μg dose of mRNA-1010 did 
not meet the Sponsor's desired 
reactogenicity profile. The 
Sponsor intends to test a lower 
dose level of 25 µg in lieu of 
200 µg, keeping the previous 
dose levels of 50 and 100 µg 
unchanged. 
Table 1: Phase 1/2 - Schedule 
of Events; Table 2: Phase 2 
Northern Hemisphere - 
Schedule of Events; Section 
6.5.2. Concomitant 
Medications and Therapies 
• Specified that all nonstudy 
vaccinations will be recorded 
throughout the study 
• To specify that nonstudy 
vaccinations should be reported 
if received at any point during 
the study. 
Figure 2: Phase 2 Northern 
Hemisphere – Study Schema 
• Updated the Phase 2 NH part of the 
study to include 3 dose levels of 
mRNA-1010 (25, 50, and 100 µg total 
mRNA) 
• Revised for consistency of 
presentation. 
Section 2.3.3. (Overall 
Benefit/Risk Conclusion) 
• Explanation of the differences in 
dosing between Phase 1/2 and Phase 2 
NH 
• Revised for consistency of 
presentation and to provide 
context. 
Table 5: Vaccination Groups 
and Dose Levels 
• Table split into Table 5a presenting 
dosing in Phase 1/2 and Table 5b 
presenting dosing in Phase 2. 
• Revised for consistency of 
presentation. 

ModernaTX, Inc. 
03 Feb 2022 
Protocol: mRNA-1010-P101 Amendment 4 
mRNA-1010 
 
Confidential 
Page 148 
Section # and Name 
Description of Change 
Brief Rationale 
Section 8.1.6. (Assessments 
for Respiratory Viral 
Infections); Section 8.4.4. 
(Medically Attended Adverse 
Events) 
• Clarified that RT-PCR confirmed ILI 
and/or COVID-19 should be captured 
as MAAEs. 
• To distinguish the diagnosis 
criteria to be used  
Abbreviations: COVID-19 = coronavirus disease 2019; ILI = influenza-like illness; MAAE = medically attended adverse event; 
mRNA = messenger RNA; NH = Northern Hemisphere; RT-PCR = reverse transcription polymerase chain reaction. 

Signature Page for VV-CLIN-003485 v3.0
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Approval
04-Feb-2022 20:38:37 GMT+0000
PPD