A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose Confirmation Study to Evaluate the Safety, Tolerability, and Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 Through 65 Years and Living in Endemic and Non-Endemic Flavivirus Areas
Phase: PHASE2
Conditions: Zika Virus
Sponsor: ModernaTX, Inc.

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CLINICAL STUDY PROTOCOL 
Protocol Title: 
A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, 
Dose Confirmation Study to Evaluate the Safety, Tolerability, 
and Immunogenicity of Zika Vaccine mRNA-1893 in Adults 
Aged 18 Through 65 Years and Living in Endemic and 
Non-Endemic Flavivirus Areas 
Protocol Number: 
mRNA-1893-P201 
Sponsor Name: 
Legal Registered Address: 
ModernaTX, Inc.  
200 Technology Square 
Cambridge, MA 02139 
Sponsor Contact: 
 
 
ModernaTX, Inc.  
200 Technology Square 
Cambridge, MA 02139 
Telephone: 
  
e-mail:
Regulatory Agency 
Identifier Number: 
Investigational New Drug (IND) Number: 19088 
Amendment Number: 
3 
Date of Amendment 3: 
09 Dec 2021 
Date of Amendment 2: 
27 Oct 2021 
Date of Amendment 1: 
16 Sep 2021 
Date of Original Protocol: 
21 Feb 2021 
CONFIDENTIAL 
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 Harmonised 
Tripartite Guideline E6(R2) Good Clinical Practice: Consolidated Guidance. 
NCT #: NCT04917861
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PROTOCOL APPROVAL – SPONSOR SIGNATORY 
 
Study Title: 
A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose 
Confirmation Study to Evaluate the Safety, Tolerability, and 
Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 
Through 65 Years and Living in Endemic and Non-Endemic Flavivirus 
Areas 
Protocol 
Number: 
mRNA-1893-P201 
Amendment 
Number: 
3 
Date of 
Amendment 3: 
09 Dec 2021 
 
 
Protocol accepted and approved by: 
 
See esignature and date signed 
on last page of document 
 
 
 
 
ModernaTX, Inc.  
200 Technology Square 
Cambridge, MA 02139 
Telephone: 
  
e-mail:
 
 
Date 
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DECLARATION OF INVESTIGATOR 
I have read and understood all sections of the protocol entitled, “A Phase 2, Randomized, 
Observer-Blind, Placebo-Controlled, Dose Confirmation Study to Evaluate the Safety, 
Tolerability, and Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 Through 
65 Years and Living in Endemic and Non-Endemic Flavivirus Areas,” 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), and all applicable government regulations. I will not make changes to the 
protocol before consulting with ModernaTX, Inc. or implement protocol changes without 
Institutional Review Board (IRB)/Independent Ethics Committee (IEC) approval except to 
eliminate an immediate risk to participants.  
I agree to administer study treatment only to participants under my personal supervision or the 
supervision of a 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/IEC. I agree 
to ensure that this information will not be used for any purpose other than the evaluation or conduct 
of the clinical investigation without the prior written consent from ModernaTX, Inc. I will not 
disclose information regarding this clinical investigation or publish results of the investigation 
without authorization from ModernaTX, Inc. 
The signature below provides the necessary assurance that this study will be conducted according 
to all stipulations of the protocol, including statements regarding confidentiality, and according to 
local legal and regulatory requirements, US federal regulations, and ICH E6(R2) GCP guidelines. 
Signature of Principal Investigator 
 
 
Date 
 
 
 
 
 
Printed Name of Principal Investigator  
 
 

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PROTOCOL AMENDMENT SUMMARY OF CHANGES 
DOCUMENT HISTORY 
Document 
Date 
Amendment 3 
09 Dec 2021 
Amendment 2 
27 Oct 2021 
Amendment 1 
16 Sep 2021 
Original Protocol 
21 Feb 2021 
 
Amendment 3 (09 Dec 2021): Current Amendment 
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1. 
PROTOCOL SUMMARY 
1.1. 
Synopsis 
Name of 
Sponsor/Company:  
ModernaTX, Inc. 
Name of Investigational 
Product:  
mRNA-1893 Injection 
Protocol Title: 
A Phase 2, Randomized, Observer-Blind, Placebo-Controlled, Dose 
Confirmation Study to Evaluate the Safety, Tolerability, and 
Immunogenicity of Zika Vaccine mRNA-1893 in Adults Aged 18 
Through 65 Years and Living in Endemic and Non-Endemic 
Flavivirus Areas 
Protocol Number: 
mRNA-1893-P201 
Study Period (Months): 
Approximately 25 months 
Phase of Development: 
2 
Study Sites: 
Clinical sites in both endemic and non-endemic Zika regions 
Objectives: 
Primary Objectives 
• 
To evaluate the safety, tolerability, and reactogenicity of 2 dose 
levels of messenger RNA (mRNA)-1893 Zika vaccine, 
administered in a 1-dose (
 µg) or 2-dose schedule (
 µg or 
 µg dose level) given 28 days apart, in comparison to a 
placebo control. 
• 
To evaluate the immunogenicity of 2 dose levels of mRNA-1893 
Zika vaccine, administered in a 1-dose (
 µg) or 2-dose 
schedule (
 µg or
 µg dose level) given 28 days apart, as 
measured by Zika virus (ZIKV)-specific neutralization assay 
(plaque reduction neutralization [PRNT]), in comparison to a 
placebo control at Day 57. 
Secondary Objectives 
• 
To evaluate the immunogenicity of 2 dose levels of mRNA-1893, 
as measured by ZIKV-specific neutralization assay (PRNT and 
microneutralization [MN]), in comparison to a placebo control, 
in flavivirus-seronegative participants at baseline and in 
flavivirus-seropositive participants at baseline. 
Exploratory Objectives 
• 
To evaluate the duration of the humoral immune response of 
2 dose levels of mRNA-1893 at Days 85, 196, 364, 532, and 700, 
as measured by ZIKV-specific neutralization assay (PRNT and 
MN), 
in 
comparison 
to 
a 
placebo 
control, 
in 
flavivirus-seronegative 
participants 
at 
baseline 
and 
in 
flavivirus-seropositive participants at baseline. 
• 
To evaluate the humoral immunogenicity of 2 dose levels of 
mRNA-1893, as measured by reporter virus particle (RVP) and 
by ligand binding assay, in comparison to a placebo control, in 
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flavivirus-seronegative 
participants 
at 
baseline 
and 
in 
flavivirus-seropositive participants at baseline. 
• 
To evaluate the ZIKV-specific cellular immune response of 
2 dose levels of mRNA-1893 in comparison to a placebo control 
in 
flavivirus-seronegative 
participants 
at 
baseline 
and 
flavivirus-seropositive participants at baseline (cell-mediated 
immunity [CMI] subset of participants).  
• 
To assess the occurrence of flavivirus infections throughout the 
entire course of participation in the study in comparison to a 
placebo control. 
Endpoints: 
Primary Safety Endpoints 
• 
Solicited local and systemic adverse reactions (ARs) through 
7 days after each investigational product (IP) injection. 
• 
Unsolicited adverse events (AEs) through 28 days after each IP 
injection.  
• 
Medically attended AEs (MAAEs) throughout the entire study 
period. 
• 
Serious AEs (SAEs) and adverse events of special interest 
(AESIs) throughout the entire study period. 
Primary Immunogenicity Endpoints 
• 
Geometric mean titer (GMT) of ZIKV-specific neutralizing 
antibodies (nAbs) at Day 57, as measured by PRNT, in all 
participants, in initially flavivirus-seronegative, and in initially 
flavivirus-seropositive participants. 
• 
Seroconversion from Day 1 to Day 57 (seroconversion is defined 
as either an increase in ZIKV-specific nAb titer from below the 
lower limit of quantification [LLOQ] to a titer equal to or above 
LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb 
titer in participants with pre-existing nAb titers [as measured by 
PRNT]). 
Secondary Immunogenicity Endpoints 
• 
GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, and 57 (Day 57 
only for MN), as measured by PRNT and MN. 
• 
GMT of ZIKV-specific nAbs in initially flavivirus-seronegative 
participants at Days 1, 8, 29, 36, and 57 (Day 57 only for MN), 
as measured by PRNT and MN. 
• 
GMT of ZIKV-specific nAbs in initially flavivirus-seropositive 
participants at Days 1, 8, 29, 36, and 57 (Day 57 only for MN), 
as measured by PRNT and MN. 
• 
Geometric mean fold rise (GMFR) of ZIKV-specific nAbs in all 
participants, in initially flavivirus-seronegative and in initially 
flavivirus-seropositive participants at Days 8, 29, 36, and 57, as 
measured by PRNT and MN. 
• 
Seroconversion from Day 1 (baseline) to Days 8, 29, 36, and 57 
(only for MN), as measured by PRNT and MN. 

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• 
Seroresponse at Days 8, 29, 36, and 57 (Day 57 only for MN) in 
flavivirus-seronegative participants at baseline (seroresponse is 
defined as an increase in ZIKV-specific nAb titer [as measured 
by PRNT or MN] from below the LLOQ to greater than or equal 
to the LLOQ). 
• 
Increase from baseline of 2-fold or 4-fold in ZIKV-specific nAb 
titers at Days 8, 29, 36, and 57, as measured by PRNT and MN, 
in flavivirus-seropositive participants at baseline. 
Exploratory Immunogenicity Endpoints 
• 
GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 700, 
as measured by PRNT and MN. 
• 
GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 700, 
as measured by PRNT and MN, in flavivirus-seronegative 
participants at baseline.  
• 
GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 700, 
as measured by PRNT and MN, in flavivirus-seropositive 
participants at baseline.  
• 
GMFR of ZIKV-specific nAbs in all participants, in initially 
flavivirus-seronegative, and in initially flavivirus-seropositive 
participants at Days 85, 196, 364, 532, and 700, as measured by 
PRNT and MN. 
• 
Seroconversion from Day 1 (baseline) to Days 85, 196, 364, 532, 
and 700, as measured by PRNT and MN. 
• 
Seroresponse at Days 85, 196, 364, 532, and 700, as measured by 
PRNT and MN, in flavivirus-seronegative participants at 
baseline.  
• 
Increase from baseline of 2-fold or 4-fold in ZIKV-specific nAb 
titers at Days 85, 196, 364, 532, and 700, as measured by PRNT 
and MN, in flavivirus-seropositive participants at baseline.  
• 
Proportion of all participants, of baseline flavivirus-seronegative 
participants, and of baseline flavivirus-seropositive participants 
with a ZIKV-specific nAb titer equal or greater than a nAb titer 
defined as a protective level in an animal model, at baseline, and 
Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as measured by 
PRNT. 
• 
Proportion of all participants, of baseline flavivirus-seronegative 
participants, and of baseline flavivirus-seropositive participants 
with a ZIKV-specific nAb titer equal or greater than a nAb titer 
defined as a protective level in an animal model, at baseline, and 
Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as measured by 
MN. 
• 
GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by RVP.  
• 
GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 
532, 
and 
700, 
as 
measured 
by 
RVP, 
in 
flavivirus-seronegative participants at baseline.  

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• 
GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 
532, 
and 
700, 
as 
measured 
by 
RVP, 
in 
flavivirus-seropositive participants at baseline.  
• 
Seroconversion from Day 1 (baseline) to Days 8, 29, 36, 57, 85, 
196, 364, 532, and 700, as measured by RVP. 
• 
Seroresponse at Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, 
as measured by RVP in flavivirus-seronegative participants at 
baseline.  
• 
Increase from baseline of 2-fold or 4-fold in ZIKV-specific nAb 
titers at Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as 
measured by RVP in flavivirus-seropositive participants at 
baseline. 
• 
Geometric mean concentration (GMC) of ZIKV-specific serum 
ligand binding antibodies (bAbs) at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by ligand binding assay. 
• 
GMC of ZIKV-specific bAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by ligand binding assay, in 
flavivirus-seronegative participants at baseline. 
• 
GMC of ZIKV-specific bAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532 and 700, as measured by ligand binding assay, in 
flavivirus-seropositive participants at baseline. 
• 
Seroconversion from Day 1 (baseline) to Days 8, 29, 36, 57, 85, 
196, 364, 532, and 700, as measured by ligand binding assay. 
• 
Seroresponse at Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, 
as measured by ligand binding assay, in flavivirus-seronegative 
participants at baseline. 
• 
Increase from baseline 2-fold or 4-fold in bAb concentrations at 
Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as measured by 
ligand binding assay, in flavivirus-seropositive participants at 
baseline. 
• 
Frequency of ZIKV-specific T cells at Days 1 (baseline), 29, 36, 
57, 196, 364, 532, and 700, as measured by intracellular cytokine 
staining assay and sequencing (CMI subset of baseline flavivirus-
seronegative and -seropositive participants). 
• 
Frequency of ZIKV-specific B cells at Days 1 (baseline), 29, 36, 
57, 196, 364, 532, and 700, as measured by ELISpot (CMI subset 
of 
baseline 
flavivirus-seronegative 
and 
-seropositive 
participants). 
• 
Additional assays to profile the T- and B-cell responses may also 
be performed (CMI subset of baseline flavivirus-seronegative 
and -seropositive participants). 
• 
GMC of nonstructural protein 1 (NS1) -specific serum bAbs at 
Days 1 (baseline), 85, 196, 364, 532, and 700, as measured by 
enzyme-linked immunosorbent assay (ELISA).  
• 
Seroconversion (NS1-specific bAbs) from Day 1 (baseline) to 
Days 85, 196, 364, 532, and 700. 

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Overall Study Design: 
All participants will be evaluated for their eligibility for enrollment 
in the Vaccination Period and will be followed for approximately 
6 months (Day 196) after their last IP injection. All participants in all 
treatment arms will have the opportunity to continue to be followed 
as part of an approximately 24-month Extension Period (through 
Day 700) after their last IP injection. 
A total of approximately 800 participants will be randomly assigned 
to receive either 
 µg or 
 µg mRNA-1893 administered as a 
2-dose regimen with at least a 28-day interval between vaccinations 
(Treatment Arm A or Treatment Arm B), or 
 µg mRNA-1893 
administered as a 1-dose regimen (Treatment Arm C), or placebo 
control administered as a 2-dose regimen with at least a 28-day 
interval between doses (Treatment Arm D) according to a 1:1:1:1 
randomization ratio (ie, 200 participants per treatment arm with 
approximately 100 participants per baseline flavivirus serostatus in 
each treatment arm). Randomization was stratified by participants’ 
baseline flavivirus serostatus in the original protocol (dated 
21 Feb 2021). 
Under 
this 
current 
protocol 
amendment, 
randomization will be stratified only by participants’ region 
(continental United States [US] and Puerto Rico). All treatment arms 
will be enrolled in parallel. In order to maintain the blinding and to 
have the same study evaluation time point with both mRNA-1893 
dose regimens relative to the last IP injection, participants randomly 
assigned to Treatment Arm C will be administered placebo at Day 1 
and mRNA-1893 at Day 29.  
Participants will be observed for immediate safety assessment for 
30 minutes after IP injection. They will be asked to record solicited 
local and systemic ARs within 7 days after each administration and 
unsolicited AEs within 28 days after each administration by 
completing eDiaries. They will also be asked to report any SAEs, 
AESIs, or MAAEs from first vaccination until End of Study (up to 
24 months after the last IP injection).  
Blood samples will be collected from all participants for 
immunogenicity analyses. A subset of participants identified as the 
“CMI subset”, approximately 20 participants per treatment arm per 
serostatus subgroup (approximately 160 participants in total), will be 
selected from approximately 4 sites that have experience in human 
cell collection. Peripheral blood mononuclear cells (PBMCs) will be 
isolated from blood samples from the CMI subset participants and 
evaluated for cellular immunity up to Day 196 with an optional 
participation every 6 months up to Day 700 for the participants 
included in the Extension Period. 
All participants will have up to 8 clinic visits (Days 0 [Eligibility 
Visit], 1 [baseline], 8, 29, 36, 57, 85, and 196) and 3 safety telephone 
calls (Days 112, 140, and 168). Participants who continue into the 
Extension Period will have 3 additional clinic visits at Days 364, 532, 
and 700. 
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Participants who withdraw from further IP injection for any reason 
after their first IP injection but do not withdraw consent will complete 
all study procedures through the End of Study (EOS) Visit. 
Study Safety Oversight: 
Study safety will be monitored by an Oversight Safety Team that will 
include the investigators participating in the study and the protocol 
team, which will include the contract research organization (CRO) 
Medical Monitor and the Sponsor Clinical Development Physician 
and may include additional representatives from the Sponsor Project 
Team. The CRO Medical Monitor will be responsible for performing 
a review of the enrollment and study-related safety data with 
oversight by the Sponsor Clinical Development Physician. During 
the Vaccination Period, a formal biweekly meeting/teleconference 
will be scheduled among the CRO Medical Monitor, the Sponsor 
Clinical Development Physician, and the Lead Investigator (or 
alternate investigator) to review safety events in a blinded fashion. 
Once all participants in all treatment arms enter the Follow-Up 
Period, the interval of these meetings may be extended to monthly. 
This decision will be confirmed by the protocol team. 
In addition, an independent Data Safety Monitoring Board (DSMB) 
will be established for Study mRNA-1893-P201. It will be composed 
of experts with experience in clinical development and vaccines and 
with expertise in flaviviruses. Members of the DSMB will be 
independent from the study conduct and free of conflict of interest. 
The DSMB will convene on an approximately quarterly basis until 
study end. Additionally, the DSMB may convene at any time if there 
is an ad-hoc safety concern detected by the protocol team. This 
independent board will be informed of the progress and conduct of 
the study; their primary responsibility will be to review unblinded 
study data to evaluate the safety findings. All AEs, SAEs, AESIs and 
MAAEs will be reviewed by the board, and they will be asked to 
provide recommendations and guidance as to management of 
follow-up within the study. In addition, should immunogenicity 
findings request further opinion, the DSMB would be asked to review 
unblinded immunogenicity data and provide guidance. 
Study Duration: 
The planned study duration will be approximately 6 months for all 
participants. Additionally, all participants will have the opportunity 
to provide their consent to participate in the Extension Period of up 
to approximately 24 months (through Day 700) after their last IP 
injection. 
Population: 
The study will enroll approximately 800 adult participants aged 18 
through 65 years at baseline, including approximately 400 
flavivirus-seropositive participants and 400 flavivirus-seronegative 
participants, who will receive mRNA-1893 or placebo. 
Flavivirus serology testing (to determine if a participant is flavivirus 
seronegative or flavivirus seropositive at baseline) is not an 
enrollment criterion. A dengue rapid point-of-care test initially used 
to stratify study participants has been discontinued. After this 
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geographic region, assuming most of the baseline seronegatives will 
come from the continental US sites and baseline seropositives from 
Puerto Rico. The confirmation will be based on flavivirus serology 
testing (dengue immunoglobulin G (IgG) and immunoglobulin M 
(IgM), West Nile IgG and IgM) performed on a blood sample 
collected prior to administration of the first vaccination, with a goal 
of an approximately equal distribution of participants among 
seronegative and seropositive participants within each treatment 
group. 
Number of Participants: 
Approximately 800 
Sample Size    
Determination: 
The sample size for this study is not driven by statistical assumptions 
for formal hypothesis testing. This sample size is regarded as 
sufficient to provide an understanding of the safety profile of 
mRNA-1893 and to confirm the dose selection to advance 
development into future studies.  
Approximately 800 participants will be randomly assigned in a 
1:1:1:1 ratio to the 4 treatment arms. A total of 600 participants will 
receive mRNA-1893, 200 participants in each dosing arm, with 
approximately 100 participants in each flavivirus serostatus cohort 
and dosing arm; approximately 200 participants will receive placebo. 
A sample size of 200 (or 400) has at least a 95% probability to 
observe at least 1 participant with an AE at a true 1.49% (or 0.75%) 
AE rate. 
For the comparison of immunogenicity, the sample size will provide 
adequate statistical power (approximately 90%) to detect a large 
effect size (4-fold or above in ZIKV-specific nAb titers, as measured 
by PRNT50 at Day 57) under reasonable assumptions. 
Inclusion Criteria: 
Participants are eligible to be included in the study only if all the 
following criteria apply: 
1. Male or female participant aged 18 through 65 years at the time 
of consent. 
2. Understands and agrees to comply with the study procedures and 
provides written informed consent. 
3. According to investigator assessment, is in good general health 
and can comply with study procedures. 
4. Female participants of nonchildbearing potential may be enrolled 
in the study. Nonchildbearing potential is defined as surgically 
sterile (history of bilateral tubal ligation, bilateral oophorectomy, 
hysterectomy) or postmenopausal (defined as amenorrhea for 
≥ 12 consecutive months prior to the eligibility evaluation 
without an alternative medical cause). The follicle-stimulating 
hormone level may be measured at the discretion of the 
investigator to confirm postmenopausal status. 
5. Female participants of childbearing potential may be enrolled in 
the study if the participant: 1) has a negative pregnancy test at the 
Eligibility Visit and on the day of the first IP injection, 2) has 
practiced adequate contraception or has abstained from all 

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activities that could result in pregnancy for at least 28 days prior 
to the first IP injection, 3) has agreed to continue adequate 
contraception through 3 months following the last IP injection, 
and 4) is not currently breastfeeding.  
Adequate female contraception is defined as consistent and 
correct use of a Food and Drug Administration-approved 
contraceptive method in accordance with the product label. 
Examples are as follows: 
• 
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 
intramuscular (IM) route. 
• 
Sterilization of a female participant’s monogamous male 
partner prior to entry into the study. 
Note: periodic abstinence (eg, calendar ovulation, 
symptothermal post-ovulation methods) and withdrawal are not 
acceptable methods of contraception.  
Exclusion Criteria: 
Participants are excluded from the study if any of the following 
criteria apply: 
1. Is acutely ill or febrile (temperature ≥ 38.0℃/100.4°F) on the day 
of the first or second vaccination. Participants meeting either of 
these criteria may be rescheduled for enrollment/randomization 
if the event resolves within the vaccination window. 
2. Had prior administration of a ZIKV vaccine candidate during a 
clinical study investigation. 
3. Had prior administration of a marketed dengue vaccine or dengue 
vaccine candidate under clinical study investigation. 
4. Has a body mass index (BMI) from ≤ 18 or ≥ 35 kg/m2. 
5. History of myocarditis, pericarditis, or myopericarditis.  
6. History of a diagnosis or condition that, in the judgement of the 
investigator, is clinically unstable or may affect participant 
safety, assessment of safety endpoints, assessment of immune 
response, or adherence to study procedures. “Clinically unstable” 
is defined as a diagnosis or condition requiring significant 
changes in management or medication within the 2 months prior 
to screening and includes ongoing work-up of an undiagnosed 
illness that could lead to a new diagnosis or condition. 
7. Any medical, psychiatric, or occupational condition, including 
reported history of drug or alcohol abuse, that in the opinion of 
the investigator, might pose a risk due to participation in the 
study or could interfere with the interpretation of study results. 
8. Has a known or suspected autoimmune disease, including 
hypothyroidism in relation to autoimmune thyroiditis. 

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9. Has a history of progressive or severe neurologic disorder or a 
history of neuroinflammatory disease such as Guillain-Barré 
Syndrome. 
10. Has a history of anaphylaxis, urticaria, or other significant AR 
requiring medical intervention after receipt of a vaccine, 
including an mRNA vaccine or any components of an mRNA 
vaccine. 
11. Has a bleeding disorder that is considered a contraindication to 
IM injection or phlebotomy. 
12. Has been diagnosed with malignancy within the previous 10 
years (excluding nonmelanoma skin cancer). 
13. Has received or plans to receive a nonstudy vaccine (including 
authorized or approved vaccines for the prevention of 
coronavirus disease 2019 [COVID-19]) ≤ 28 days prior to the 
first IP injection or within 28 days prior to or after any IP 
injection. Licensed influenza vaccine received within 14 days 
prior to the first IP injection or plans to receive a licensed 
influenza vaccine 14 days prior to through 14 days following 
each IP injection are not exclusionary. 
14. Has a known or suspected impairment or alteration of immune 
function including the following: 
a. Chronic use of oral steroids (equivalent to 20 mg/day 
prednisone ≥ 12 weeks or ≥ 2 mg/kg body weight/day 
prednisone ≥ 2 weeks) within 60 days prior to Day 1 (use of 
inhaled, intranasal, or topical corticosteroids is allowed). 
b. Receipt of parenteral steroids (equivalent to 20 mg/day 
prednisone ≥ 12 weeks or ≥ 2 mg/kg body weight/day 
prednisone ≥ 2 weeks) within 60 days prior to Day 1. 
c. Receipt of immunosuppressive therapy within 3 months prior 
to Day 1 or planned during the 7-month period following 
study enrollment. 
d. Receipt of immunostimulants within 60 days prior to Day 1. 
e. Receipt 
of 
parenteral, 
epidural, 
or 
intra-articular 
immunoglobulin preparation, blood products, and/or plasma 
derivatives within 3 months prior to Day 1 or planned during 
the 7-month period following study enrollment. 
f. HIV infection or HIV-related disease. 
g. Genetic immunodeficiency. 
15. Has received systemic immunoglobulins or blood products 
within 3 months prior to the day of enrollment or planned during 
the 7-month-period following study enrollment. 
16. Has donated ≥ 450 mL of blood products within 28 days of the 
Day 1 Visit. 
17. Has participated in an interventional clinical study within 28 days 
prior to the day of enrollment or plans to do so while enrolled in 
this study. 

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18. Is an immediate family member or household member of study 
personnel. 
Investigational Products, 
Dosage, and Route of 
Administration: 
mRNA-1893 consists of a messenger RNA sequence that encodes the 
full pre-membrane and envelope structural polyprotein of ZIKV in a 
liposomal formulation. 
The lipid nanoparticle formulation includes 4 lipid excipients (1 
proprietary and 3 commercially available). mRNA-1893 will be 
provided as a 0.20 mg/mL dispersion in 2R glass vials labeled as 
required per country requirement. The vaccine will be diluted with 
0.9% sodium chloride solution for injection (United States 
Pharmacopeia [USP] or British Pharmacopeia [BP]) to a 
concentration for delivery of the specified dose level in a volume of 
0.5 mL. 
The IP will be administered as an IM injection into the deltoid muscle 
on a 2-dose dose schedule on Days 1 and 29, with at least a 28-day 
interval between doses. Each dose will have a volume of 0.5 mL and 
will contain either mRNA-1893 
 µg or mRNA-1893 
 µg, or 
placebo. Preferably, the first dose should be injected into the 
nondominant arm. The second dose should be injected into the same 
arm as the first dose. 
The placebo is 0.9% sodium chloride solution for injection, USP or 
BP. 
Unblinded pharmacy personnel, who will not participate in any other 
aspect of the study, will perform IP accountability, IP preparation, 
and administration. 
Assessments and 
Procedures: 
Safety Assessments:  
Safety assessments will include monitoring and recording of the 
following for each participant: 
• 
Solicited local and systemic ARs that occur during the 7 days 
following each IP injection (ie, the day of injection and 6 
subsequent days). Solicited ARs will be recorded daily using 
electronic diaries (eDiaries). 
• 
Unsolicited AEs observed or reported during the 28 days 
following each IP injection (ie, the day of injection and 27 
subsequent days). Unsolicited AEs are AEs that are not included 
in the protocol-defined solicited ARs.  
• 
AEs leading to discontinuation from IP and/or study participation 
throughout the entire study duration (up to Day 700).  
• 
MAAEs from Day 1 throughout the entire study duration (up to 
Day 700). 
• 
SAEs and AESIs from Day 1 throughout the entire study duration 
(up to Day 700). 
• 
Physical examination findings.  
• 
Vital sign measurements. 
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Immunogenicity Assessments: 
Immunogenicity assessments will include the following:  
• 
Serum ZIKV-specific nAb titers, as measured by PRNT assay, 
MN assay, and RVP assay.  
• 
Serum ZIKV-specific bAb concentrations, as measured by ligand 
binding assay. 
• 
Frequency of ZIKV-specific T cells, as measured by ICS assay 
and sequencing and frequency of ZIKV-specific B cells, as 
measured by ELISpot. Other techniques that may be relevant to 
assess the profile characteristics of the ZIKV-specific T- and 
B-cell responses may be included. 
Efficacy Assessments: 
• 
Asymptomatic 
flavivirus 
infections, 
assessed 
through 
quantification of NS1 bAbs, as measured by ELISA. 
• 
Symptomatic flavivirus infections, assessed by specific serology 
(IgM antibody capture ELISA and virus neutralization assay) 
and RT-PCR. 
Statistical Plan: 
Populations for Analyses:  
• 
The Randomized Set consists of all participants who are 
randomized in the study, regardless of the participant’s treatment 
status in the study. Participants will be included in the treatment 
arm to which they are randomized. 
• 
The Solicited Safety Set consists of all participants who are 
randomly assigned and received any IP and contribute any 
solicited AR data. The Solicited Safety Set will be used for the 
analyses of solicited ARs and participants will be included in the 
treatment arm corresponding to the IP they actually received. 
• 
The Safety Set consists of all participants who are randomly 
assigned and received any IP. The Safety Set will be used for 
analysis of safety except for the solicited ARs. Participants will 
be included in the treatment arm corresponding to the IP they 
actually received for the analysis of safety data using the Safety 
Set. 
• 
The Full Analysis Set (FAS) consists of all participants who are 
randomly assigned and a) received any IP, b) have baseline (Day 
1) data available for those analyses that require baseline data, and 
c) have at least 1 post-IP injection assessment for those analysis 
endpoints as specified in b). Participants will be included in the 
treatment arm to which they are randomly assigned. 
• 
The Per-Protocol (PP) Set consists of all FAS participants who 
a) comply with the vaccination schedule, b) comply with the 
timings of immunogenicity blood sampling to have post-IP 
injection results available for at least 1 assay component 
corresponding to the immunogenicity analysis objective, and c) 
have no major protocol deviations that impact immune response 
during the period corresponding to the immunogenicity analysis 
objective. The PP set will serve as the primary population for the 

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analysis of immunogenicity data in this study. Participants will 
be included in the treatment arm to which they are randomly 
assigned. 
Safety Analyses: 
Safety analyses will include solicited ARs (local and systemic), 
unsolicited AEs, SAEs, AESIs, MAAEs, and AEs leading to 
vaccine/study withdrawal, and vital sign measurements. 
Solicited ARs, unsolicited AEs, and vital sign measurements will be 
graded according to the Toxicity Grading Scale for Healthy Adult 
and Adolescent Volunteers Enrolled in Preventive Vaccine Clinical 
Trials (DHHS 2007). 
All safety analyses will be based on the Safety Set, except analyses 
of solicited ARs which will be based on the Solicited Safety Set. All 
safety analyses will be provided by treatment arm overall (regardless 
of serostatus) and by baseline flavivirus status assessed by dengue 
and West Nile specific serologies, and vaccination (first, second), 
unless otherwise specified. 
Solicited local and systemic ARs during the 7-day follow-up period 
after each IP injection will be tabulated by number and percentage of 
participants reporting ≥ 1 event. The number and percentage of 
participants with any solicited local AR, with any solicited systemic 
AR, and with any solicited AR during the 7-day follow-up period 
after each IP injection will be provided with a 2-sided 95% exact CI 
using the Clopper-Pearson method. 
Unsolicited AEs will be coded according to the Medical Dictionary 
for Regulatory Activities (Dictionary for Adverse Reaction 
Terminology version). Unsolicited AEs, treatment-related AEs, 
SAEs, AESIs, MAAEs, and AEs leading to discontinuation from IP 
or participation in the study, severe AEs, and deaths will be reported 
by number and percentage of participants reporting ≥ 1 event, and 
number of events. 
Demographic variables (eg, age, height, weight, and BMI) and 
baseline characteristics will be summarized by treatment arm overall 
(regardless of baseline serostatus) and by baseline flavivirus status 
assessed by dengue and West Nile specific serologies and treatment 
arm by descriptive statistics (mean, median, minimum, maximum, 
and standard deviation for continuous variable, and number and 
percentage for categorical variables). 
Further details will be described in the statistical analysis plan (SAP). 
Immunogenicity Analyses: 
Immunogenicity analyses will be conducted on the PP set, reported 
by treatment arm overall and by baseline flavivirus status assessed by 
dengue and West Nile specific serologies, as applicable. If the 
number of participants in the FAS and PP set differ by more than 
10%, supportive immunogenicity analyses may be conducted on the 
FAS. 

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For the primary and secondary immunogenicity endpoints, 
descriptive summary statistics of antibody-mediated immunogenicity 
at each time point will include GMT (for nAbs) median, minimum, 
maximum, 95% CI, and GMFR of post-baseline/baseline nAb titers.  
For GMT calculations, antibody titers reported as below the 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. 
The number and percentage of participants with seroconversion will 
be provided with 2-sided 95% CI using Clopper-Pearson method by 
treatment arm overall and also by the baseline flavivirus serostatus.  
The number and percentage of participants with seroresponse will be 
provided with 2-sided 95% CI using Clopper-Pearson method by 
treatment arm overall and in baseline flavivirus-seronegative 
participants. 
The number and percentage of participants with ≥ 2- or ≥ 4-fold rise 
in ZIKV-specific nAb titers will be provided with 2-sided 95% CI 
using Clopper-Pearson at each post-baseline timepoint. 
Further details will be described in the SAP. 
Study Planned Analyses: 
The following analyses will be conducted on cleaned data:  
1. An interim analysis (IA) of safety and immunogenicity data will 
be performed after all participants have completed Day 57 (28 
days after the last IP injection). The Day 57 IA will be performed 
by a separate team of unblinded programmers and statisticians. 
Pre-identified Sponsor team members will be unblinded to 
review treatment level results, as defined in the study Data 
Blinding Plan. The unblinded statistics team will not be involved 
in either study design or the regular study conduct. The 
participants and study sites will remain blinded until the 
conclusion of the study. The IA will serve as the basis for the 
progression to the ZIKV Phase 3 studies. 
2. The final clinical study report (CSR) will include full unblinded 
analyses of all safety and immunogenicity with individual 
unblinded listings through Day 196 (all data through 
approximately 6 months after the last IP injection).  
3. An addendum to the CSR will include the safety and 
immunogenicity data from Month 8 until EOS for all participants 
enrolled in the Extension Period.  
More details can be found in the SAP. 
In addition, unblinded data presentation or analysis for DSMB review 
will be handled by the unblinded team of statisticians and 
programmers, who are not involved in study design. More details 
regarding DSMB analysis can be found in the DSMB Charter. 

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1.2. 
Schema 
Figure 1: Study Schema 
 
Abbreviations: mRNA = messenger RNA. 
Note: Participants randomly assigned to Treatment Arm C will be administered placebo at Day 1 and mRNA-1893 
 µg at Day 29.
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1.3. 
Schedule of Assessments 
The Schedules of Assessments for the Vaccination Period and the Extension Period are presented in Table 1 and Table 2, respectively. 
If a participant cannot attend a study site visit (scheduled or unscheduled) with the exception of Day 0, Day 1, and Day 29 Visits, a 
home visit is acceptable if performed by appropriately delegated study site staff or a home healthcare service provided by the Sponsor. 
If neither a participant visit to the study site nor a home visit to the participant is possible (with the exception of Day 0, Day 1, and 
Day 29 Visits), a safety telephone call should be performed that includes the assessments scheduled for the safety telephone calls 
scheduled on Days 112 through 168 (Table 1). 
Table 1: Schedule of Assessments for the Vaccination Period and for the Follow-Up Period (Approximately 6 Months) 
Procedure 
Eligibility 
Vaccination Period 
Follow-Up 
Period 
Unscheduled 
Study Day 
D01 
(Eligibility) 
D11 
(Baseline) 
D8 
D29 
D36 
D57 
D85 
D112, 
D140, 
D168 
D196 
 
Visit Number 
0  
1 
2 
3 
4 
5 
6 
7-9 
10  
and 
EOS2 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
C 
C 
C 
SC 
C 
C 
Window Allowance (Days) 
-8 
 
+3 
-3/+7 
+3 
-3/+7 
-3/+7 
 ± 15 
 ± 15 
 
Informed consent, inclusion and 
exclusion criteria, demography, prior 
and concomitant medications, and 
medical history 
X 
 
 
 
 
 
 
 
 
 
Physical examination and vital sign 
measurements3 
X 
X 
(X) 
X 
(X) 
X 
(X) 
 
(X) 
(X) 
Blood sample for baseline flavivirus 
serostatus assessments4, 5 
 
X 
 
 
 
 
 
 
 
 

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Procedure 
Eligibility 
Vaccination Period 
Follow-Up 
Period 
Unscheduled 
Study Day 
D01 
(Eligibility) 
D11 
(Baseline) 
D8 
D29 
D36 
D57 
D85 
D112, 
D140, 
D168 
D196 
 
Visit Number 
0  
1 
2 
3 
4 
5 
6 
7-9 
10  
and 
EOS2 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
C 
C 
C 
SC 
C 
C 
Window Allowance (Days) 
-8 
 
+3 
-3/+7 
+3 
-3/+7 
-3/+7 
 ± 15 
 ± 15 
 
Blood sample for antibody-mediated 
immunogenicity6 
 
X 
X 
X 
X 
X7 
X 
 
X 
 
PBMC collection for cellular 
immunity (subset of participants from 
approximately 4 selected sites) 
 
X 
 
X 
X 
X 
 
 
X 
 
Pregnancy test8 
X 
X 
 
X 
 
 
 
 
 
 
Randomization 
 
X 
 
 
 
 
 
 
 
 
IP injection (including 30-minute 
safety observation period after IP 
injection)9 
 
X 
 
X 
 
 
 
 
 
 
Participant eDiary recording of 
solicited ARs (7 days) 
 
X 
(Days 1-7) 
 
X 
(Days 29-35) 
 
 
 
 
 
 
Participant eDiary recording of 
unresolved solicited ARs (up to 28 
days) 
 
X 
(Days 1-29 and Days 29-57) 
 
 
 
 
Review of eDiary 
 
 
X 
 
X 
 
 
 
 
 
Follow-up safety telephone call10 
 
 
 
 
 
 
 
X 
 
 
Recording of MAAEs 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Recording of SAEs and AESIs 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 

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Procedure 
Eligibility 
Vaccination Period 
Follow-Up 
Period 
Unscheduled 
Study Day 
D01 
(Eligibility) 
D11 
(Baseline) 
D8 
D29 
D36 
D57 
D85 
D112, 
D140, 
D168 
D196 
 
Visit Number 
0  
1 
2 
3 
4 
5 
6 
7-9 
10  
and 
EOS2 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
C 
C 
C 
SC 
C 
C 
Window Allowance (Days) 
-8 
 
+3 
-3/+7 
+3 
-3/+7 
-3/+7 
 ± 15 
 ± 15 
 
Recording of concomitant 
medications and nonstudy 
vaccinations 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Blood sample for asymptomatic 
flavivirus infection detection11 
 
 
 
 
 
 
X 
 
X 
 
Blood sample for symptomatic 
flavivirus infection detection11 
 
 
 
 
 
 
 
 
 
X 
Informed consent to participate in the 
Extension Period 
 
 
 
 
 
 
 
 
X12 
 
Abbreviations: AE = adverse event; AESIs = adverse events of special interest; AR = adverse reaction; C = clinic visit; CMI = cell-mediated immunity; D = day; eDiary = 
electronic diary; EOS = End of Study; IP = investigational product; MAAE = medically attended adverse event; mRNA = messenger RNA; PBMC = peripheral blood mononuclear 
cell; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event; SC = safety (phone) call; US = United States. 
1 
The Eligibility (Day 0) and Baseline (Day 1) Visits may be combined on the same day. 
2 
This visit will be the EOS for all enrolled participants who do not elect to continue into the Extension Period. For participants enrolled in Treatment Arm A (2-dose regimen 
with 
 μg mRNA-1893), Treatment Arm B (2-dose regimen with 
 μg mRNA-1893), Treatment Arm C (1-dose regimen with 
 μg mRNA-1893), and Treatment Arm D 
(placebo) who elect to take part in the Extension Period, return visits will occur approximately every 6 months after the last IP injection (Table 2). 
3 
A full physical examination, including weight, and vital sign measurements will be performed at the eligibility evaluation and Days 1, 29, and 57. Height measurements will 
only be collected at Day 1. Symptom-directed physical examinations may be performed at other scheduled timepoints (X) at the discretion of the investigator. Vital sign 
measurements (body temperature, systolic and diastolic blood pressure, heart rate, and respiratory rate) will be collected before study procedures and at least 30 minutes after 
IP injection, prior to discharge of the participant from the study site. Any clinically significant finding identified during a study visit should be reported as an MAAE. Body 
mass index will be calculated (Section 8.5.3) during the eligibility evaluation. 
4 
Flavivirus serology testing is to determine if a participant is flavivirus seronegative or flavivirus seropositive at baseline. This is not an enrollment criterion. However, this 
flavivirus serology testing needs to be performed on a blood sample collected prior to administration of the first vaccination to confirm that the study distribution among 
subgroups is respected.  
5 
Follicle-stimulating hormone level may be measured to confirm menopausal status at the discretion of the investigator. 
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6 
Blood samples must be collected before injection on vaccination days (Days 1 and 29). 
7 
At Visit 5 (Day 57), an additional blood sample (60 mL) will be collected for exploratory research (Table 9 and Section 11.1.10) from participants enrolled at 1 US site. This 
site will be different from those sites selected for cellular immunity. 
8 
Pregnancy testing at the Eligibility Visit (Day 0) and before each IP injection (or at any time at the discretion of the investigator) will be a point-of-care urine test. 
9 
Participants will be administered the IP (mRNA-1893 or placebo) according to the randomization. Participant will remain at the study site for safety monitoring for at least 
30 minutes after IP injection. 
10 
Trained study personnel will call all participants to collect information relating to any MAAEs, SAEs, AESIs, AEs leading to study discontinuation, concomitant medications 
associated with those events, and any nonstudy vaccinations. 
11 
Blood samples collected from all participants at Visit 6 (Day 85) and Visit 10 (Day 196) will be used for detection of asymptomatic flavivirus infections. In case of signs or 
symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas where the study will be performed), an additional blood sample will be collected to confirm 
the diagnosis via specific serology and RT-PCR, and clinical information will be carefully collected to evaluate the severity of the clinical case. Those symptoms are not 
specific; however, an association of acute fever onset with maculopapular rash, arthralgia, and conjunctivitis during the seasonal circulation of mosquitos must trigger 
samplings. Also, special attention will be paid to the reporting of neurological signs or symptoms evoking Guillain-Barré syndrome.  
12 
At Visit 10 (Day 196), all participants will have the opportunity to provide their consent to participate in the Extension Period (Table 2). 
 

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Table 2: Schedule of Assessments for the Extension Period  
Procedure 
Extension Period 
Study Day 
D364 
D532 
D700 
 
Visit Number 
11 
12 
13 and EOS 
Unscheduled 
Type of Visit 
C 
C 
C 
C 
Window Allowance (Days) 
 ± 15 
± 15 
 ± 30 
 
Physical examination (including weight) and vital sign 
measurements)1 
(X) 
(X) 
(X) 
(X) 
Blood sample for antibody-mediated immunogenicity 
X 
X 
X 
 
PBMC collection for cellular immunity (CMI subset participants 
selected during the Vaccination Period) 
X 
X 
X 
 
Blood sample for asymptomatic flavivirus infection detection2 
X 
X 
X 
 
Blood sample for symptomatic flavivirus infection detection2 
 
 
 
X 
Recording of MAAEs 
X 
X 
X 
X 
Recording of SAEs and AESIs 
X 
X 
X 
X 
Recording of concomitant medications and nonstudy vaccinations 
X 
X 
X 
X 
Study completion 
 
 
X 
 
Abbreviations: AESIs = adverse events of special interest; C = clinic visit; CMI = cell-mediated immunity; D = day; EOS = End of Study; MAAE = medically attended adverse 
event; RT-PCR = reverse transcription polymerase chain reaction; SAE = serious adverse event. 
1 
Symptom-directed physical examinations might be performed at the scheduled timepoints (X) at the discretion of the investigator. Vital sign measurements (body 
temperature, systolic and diastolic blood pressure, heart rate, and respiratory rate) will be collected before study procedures. Any clinically significant finding identified 
during a study visit should be reported as an MAAE. 
2 
Blood samples collected from all participants at Visits 11, 12, and EOS (Days 364, 532, and 700, respectively) will be used for detection of asymptomatic flavivirus 
infections. In case of signs or symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas where the study will be performed), an additional blood sample 
will be taken to confirm the diagnosis via specific serology and RT-PCR, and clinical information will be carefully collected to evaluate the severity of the clinical case. 
Special attention will be paid to collect signs or symptoms possibly related to Guillain-Barré syndrome. 
 

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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 ............................................................................................6 
1.1. 
Synopsis ........................................................................................................................6 
1.2. 
Schema ........................................................................................................................19 
1.3. 
Schedule of Assessments ............................................................................................20 
TABLE OF CONTENTS ...............................................................................................................25 
LIST OF TABLES .........................................................................................................................31 
LIST OF FIGURES .......................................................................................................................31 
LIST OF ABBREVIATIONS ........................................................................................................32 
2. 
INTRODUCTION ......................................................................................................35 
2.1. 
Study Rationale ...........................................................................................................35 
2.2. 
Background and Overview .........................................................................................35 
2.2.1. 
Nonclinical Studies .....................................................................................................36 
2.2.2. 
Clinical Studies ...........................................................................................................38 
2.3. 
Benefit/Risk Assessment ............................................................................................39 
2.3.1. 
Known Potential Benefits ...........................................................................................39 
2.3.2. 
Anticipated Risks ........................................................................................................39 
2.3.3. 
Overall Benefit/Risk Conclusion ................................................................................42 
3. 
OBJECTIVES AND ENDPOINTS ............................................................................43 
3.1. 
Primary Objectives and Endpoints .............................................................................43 
3.2. 
Secondary Objectives and Endpoints .........................................................................44 
3.3. 
Exploratory Objectives and Endpoints .......................................................................45 
4. 
STUDY DESIGN .......................................................................................................48 
4.1. 
General Design ...........................................................................................................48 
4.1.1. 
Eligibility Evaluation ..................................................................................................49 
4.1.2. 
Vaccination Period ......................................................................................................49 
4.1.3. 
Extension Period .........................................................................................................50 

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4.2. 
Scientific Rationale for Study Design ........................................................................50 
4.3. 
Justification for the Choice of Study Population ........................................................51 
4.4. 
Justification for Dose and Schedule ...........................................................................51 
4.5. 
Justification for the Use of Placebo ............................................................................52 
4.6. 
End of Study Definition ..............................................................................................52 
5. 
STUDY POPULATION .............................................................................................53 
5.1. 
Inclusion Criteria ........................................................................................................53 
5.2. 
Exclusion Criteria .......................................................................................................55 
5.3. 
Lifestyle Restrictions ..................................................................................................56 
5.4. 
Screen Failures ............................................................................................................56 
6. 
INVESTIGATIONAL PRODUCT ............................................................................57 
6.1. 
Investigational Products Administered .......................................................................57 
6.2. 
Preparation, Handling, Storage, and Accountability of Investigational 
Products ......................................................................................................................58 
6.2.1. 
Investigational Product Preparation ............................................................................59 
6.2.2. 
Investigational Product Administration ......................................................................59 
6.2.3. 
Investigational Product Packaging and Labeling .......................................................60 
6.2.4. 
Investigational Product Storage ..................................................................................60 
6.2.5. 
Investigational Product Accountability ......................................................................60 
6.2.6. 
Investigational Product Handling and Disposal .........................................................61 
6.3. 
Randomization and Blinding ......................................................................................61 
6.3.1. 
Randomization ............................................................................................................61 
6.3.2. 
Blinding ......................................................................................................................61 
6.3.3. 
Unblinding ..................................................................................................................62 
6.4. 
Investigational Product Compliance ...........................................................................62 
6.5. 
Prior and Concomitant Medications and Therapies ....................................................63 
6.5.1. 
Prior Medications and Therapies .................................................................................63 
6.5.2. 
Concomitant Medications and Therapies ....................................................................63 
6.5.3. 
Concomitant Medications and Vaccines that May Lead to the Elimination of 
a Participant from Per-Protocol Analyses ....................................................................64 
6.6. 
Intervention After the End of the Study .....................................................................64 

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7. 
DELAY OR DISCONTINUATION OF INVESTIGATIONAL PRODUCT 
AND PARTICIPANT WITHDRAWAL FROM THE STUDY ................................65 
7.1. 
Criteria for Delay of Investigational Product Administration and 
Contraindication to Subsequent Administrations .......................................................65 
7.2. 
Discontinuation of Investigational Product ................................................................65 
7.3. 
Participant Withdrawal from the Study ......................................................................66 
7.4. 
Lost to Follow-Up.......................................................................................................67 
7.5. 
Circumstances to Delay or Discontinue the Study Independent of 
Investigational Product and Participant ......................................................................68 
8. 
STUDY ASSESSMENTS AND PROCEDURES ......................................................69 
8.1. 
Demographics and Other Baseline Characteristics .....................................................69 
8.2. 
Clinical Laboratory Assessments ...............................................................................70 
8.2.1. 
Baseline and Safety Laboratory Assessments ............................................................70 
8.3. 
Immunogenicity and Efficacy Assessments ...............................................................70 
8.3.1. 
Immunogenicity Assessments ....................................................................................70 
8.3.2. 
Efficacy Assessments .................................................................................................71 
8.4. 
Total Blood Volume ...................................................................................................71 
8.5. 
Safety Assessments .....................................................................................................73 
8.5.1. 
Electronic Diary Assessments ....................................................................................74 
8.5.2. 
Safety Telephone Calls ...............................................................................................76 
8.5.3. 
Physical Examination .................................................................................................76 
8.5.4. 
Vital Sign Measurements ............................................................................................77 
8.6. 
Adverse Events and Serious Adverse Events .............................................................77 
8.6.1. 
Time Period and Frequency for Collecting AE and SAE Information .......................77 
8.6.2. 
Method of Detecting AEs and SAEs ..........................................................................78 
8.6.3. 
Follow-Up of AEs and SAEs ......................................................................................79 
8.6.4. 
Adverse Events of Special Interest .............................................................................79 
8.6.5. 
Regulatory Reporting Requirements for SAEs ...........................................................79 
8.6.6. 
Pregnancy ...................................................................................................................80 
8.7. 
Treatment of Overdose ...............................................................................................80 
8.8. 
Pharmacokinetics ........................................................................................................80 
8.9. 
Pharmacodynamics .....................................................................................................80 

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8.10. 
Biomarkers ..................................................................................................................81 
8.11. 
Medical Resource Utilization and Health Economics ................................................81 
9. 
STATISTICAL CONSIDERATIONS .......................................................................82 
9.1. 
Statistical Hypotheses .................................................................................................82 
9.2. 
Sample Size Determination ........................................................................................82 
9.3. 
Populations for Analyses ............................................................................................83 
9.3.1. 
Randomized Set ..........................................................................................................83 
9.3.2. 
Solicited Safety Set .....................................................................................................83 
9.3.3. 
Safety Set ....................................................................................................................83 
9.3.4. 
Full Analysis Set .........................................................................................................83 
9.3.5. 
Per-Protocol Set ..........................................................................................................83 
9.4. 
Statistical Analyses .....................................................................................................83 
9.4.1. 
Baseline Descriptive Statistics ....................................................................................84 
9.4.2. 
Efficacy Analyses .......................................................................................................84 
9.4.3. 
Safety Analyses ..........................................................................................................84 
9.4.4. 
Immunogenicity Analyses ..........................................................................................85 
9.5. 
Study Planned Analyses .............................................................................................86 
10. 
REFERENCES ...........................................................................................................88 
11. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS ..................................................................................................91 
11.1. 
APPENDIX 1: Study Governance Considerations .....................................................91 
11.1.1. 
Regulatory and Ethical Considerations ......................................................................91 
11.1.2. 
Study Monitoring ........................................................................................................91 
11.1.3. 
Audits and Inspections ................................................................................................93 
11.1.4. 
Financial Disclosure ...................................................................................................93 
11.1.5. 
Recruitment Procedures ..............................................................................................93 
11.1.6. 
Informed Consent Process ..........................................................................................94 
11.1.7. 
Protocol Amendments ................................................................................................95 
11.1.8. 
Protocol Violations and Deviations ............................................................................95 
11.1.9. 
Data Protection ...........................................................................................................96 
11.1.10. 
Sample Retention and Future Biomedical Research ..................................................97 

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11.1.11. 
Study Safety Oversight by Oversight Safety Team and Data Safety 
Monitoring Board .......................................................................................................98 
11.1.12. 
Dissemination of Clinical Study Data ........................................................................98 
11.1.13. 
Data Quality Assurance and Quality Control .............................................................99 
11.1.14. 
Data Collection and Management ............................................................................100 
11.1.15. 
Source Documents ....................................................................................................100 
11.1.16. 
Retention of Records ................................................................................................101 
11.1.17. 
Study and Site Closure..............................................................................................101 
11.1.18. 
Publication Policy .....................................................................................................102 
11.2. 
APPENDIX 2: Adverse Events: Definitions and Procedures for Recording, 
Evaluating, Follow-Up, and Reporting .....................................................................103 
11.2.1. 
Definition of an AE ..................................................................................................103 
11.2.2. 
Definition of an SAE ................................................................................................103 
11.2.3. 
Definition of Solicited Adverse Reactions ...............................................................105 
11.2.4. 
Definition of Medically Attended Adverse Events ..................................................106 
11.2.5. 
Definition of Adverse Events of Special Interest .....................................................106 
11.2.6. 
Recording and Follow-Up of an AE and/or SAE .....................................................106 
11.2.7. 
Pregnancy .................................................................................................................107 
11.2.8. 
Assessment of Severity .............................................................................................107 
11.2.9. 
Assessment of Causality ...........................................................................................110 
11.2.10. 
Follow-Up of AEs and SAEs ....................................................................................111 
11.2.11. 
Reporting of SAEs ....................................................................................................111 
11.2.12. 
Reporting of AESIs ...................................................................................................113 
11.2.13. 
Adverse Events of Special Interest Terms ................................................................113 
11.3. 
APPENDIX 3: Contraceptive Guidance and Collection of Pregnancy 
Information ...............................................................................................................116 
11.3.1. 
Definitions: Women of Childbearing Potential ........................................................116 
11.3.2. 
Contraception Guidance: ..........................................................................................117 
11.3.3. 
Collection of Pregnancy Information .......................................................................118 
11.4. 
APPENDIX 4: CDC Working Case Definitions of Myocarditis, Pericarditis, 
and Myopericarditis Occurring After Receipt of COVID-19 mRNA 
Vaccines ....................................................................................................................120 
11.5. 
APPENDIX 5: Protocol Amendment History ..........................................................122 

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11.5.1. 
Amendment 2 (27 Oct 2021) ....................................................................................122 
11.5.2. 
Amendment 1 (16 Sep 2021) ....................................................................................122 
 
 

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LIST OF TABLES 
Table 1: 
Schedule of Assessments for the Vaccination Period and for the Follow-Up 
Period (Approximately 6 Months) ..............................................................................20 
Table 2: 
Schedule of Assessments for the Extension Period ....................................................24 
Table 3: 
Primary Objectives and Endpoints .............................................................................43 
Table 4: 
Secondary Objectives and Endpoints .........................................................................44 
Table 5: 
Exploratory Objectives and Endpoints .......................................................................45 
Table 6: 
Treatment Arms ..........................................................................................................48 
Table 7: 
Participant Distribution by Treatment Arm ................................................................53 
Table 8: 
Investigational Products Administered .......................................................................58 
Table 9: 
Total Planned Approximate Blood Volumes for the Vaccination Period ..................72 
Table 10: Total Planned Approximate Blood Volumes for the Extension Period ......................73 
Table 11: 95% Confidence Interval for One Participant with an Adverse Event and the 
Lowest Detectable Incidence Rate at 95% Probability in Each Selected 
Sample Size ................................................................................................................82 
Table 12: Analysis Strategy for Solicited Adverse Reactions and Unsolicited Adverse 
Events Parameters .......................................................................................................85 
Table 13: Toxicity Grading .......................................................................................................108 
Table 14:    Table for Clinical Abnormalities ..............................................................................110 
Table 15:    Adverse Events of Special Interest ...........................................................................113 
Table 16: Highly Effective Methods of Contraception (< 1% Failure Rate) ............................118 
Table 17:    Case Definitions of Probable and Confirmed Myocarditis, Pericarditis, and 
Myopericarditis .........................................................................................................120 
 
LIST OF FIGURES 
Figure 1: 
Study Schema .............................................................................................................19 
 
 

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LIST OF ABBREVIATIONS 
The following abbreviations and specialist terms are used in this study protocol. 
Abbreviation or Specialist Term Definition 
AE 
Adverse event 
AESI 
Adverse event of special interest 
AR 
Adverse reaction 
bAb 
Binding antibody 
BMI 
Body mass index 
BP 
British Pharmacopeia 
CDC 
Centers for Disease Control and Prevention 
CFR 
Code of Federal Regulations 
CI 
Confidence interval 
CMI 
Cell-mediated immunity 
CMV 
Cytomegalovirus 
COVID-19 
Coronavirus disease 2019 
CRA 
Clinical research associate 
CRO 
Contract research organization 
CSR 
Clinical study report 
DSMB 
Data Safety Monitoring Board 
eCRF 
Electronic case report form 
EDC 
Electronic data capture 
eDiary 
Electronic diary 
ELISA 
Enzyme-linked immunosorbent assay 
ELISpot 
Enzyme-linked immunosorbent spot 
EOS 
End of Study 
FAS 
Full Analysis Set 
FDA 
Food and Drug Administration 
FSH 
Follicle-stimulating hormone 

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Abbreviation or Specialist Term Definition 
GCP 
Good Clinical Practice 
GLP 
Good Laboratory Practice 
GMC 
Geometric mean concentration 
GMFR 
Geometric mean fold rise 
GMT 
Geometric mean titer 
hMPV 
Human metapneumovirus 
HRT 
Hormonal replacement therapy 
IA 
Interim analysis 
IB 
Investigator’s Brochure 
ICF 
Informed consent form 
ICH 
International Council for Harmonisation 
IEC 
Independent Ethics Committee 
Ig 
Immunoglobulin 
IgG 
Immunoglobulin G 
IgM 
Immunoglobulin M 
IM 
Intramuscular(ly) 
IP 
Investigational product 
IRB 
Institutional Review Board 
IRT 
Interactive Response Technology  
LLOQ 
Lower limit of quantification 
LNP 
Lipid nanoparticle 
LOD 
Limit of detection 
LTFU 
Lost to follow-up 
MAAE 
Medically attended adverse event 
MN 
Microneutralization 
mRNA 
Messenger RNA 
nAb 
Neutralizing antibody 

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Abbreviation or Specialist Term Definition 
NS1 
Nonstructural protein 1 
OST 
Oversight safety team 
PBMC 
Peripheral blood mononuclear cell 
PIV3 
Parainfluenza virus type 3 
PP  
Per-protocol 
prME 
Pre-membrane and envelope 
PRNT 
Plaque reduction neutralization test 
QA 
Quality assurance 
RT-PCR 
Reverse transcription polymerase chain reaction 
RVP 
Reporter virus particle 
SAE 
Serious adverse event 
SAP 
Statistical analysis plan 
SARS-CoV-2 
Severe acute respiratory syndrome coronavirus 2 
SCR 
Seroconversion rate 
SM-102 
Heptadecan-9-yl 8-((2-hydroxyethyl)(6-oxo-
6(undecyloxy)hexyl)amino)octanoate 
SOA 
Schedule of Assessments 
ULOQ 
Upper limit of quantification 
US 
United States 
USP 
United States Pharmacopeia 
WHO 
World Health Organization 
ZIKV 
Zika virus 
ZPIV 
Zika virus purified inactivated vaccine 
 

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2. 
INTRODUCTION 
2.1. 
Study Rationale 
The purpose of this Phase 2 randomized, observer-blind, placebo-controlled, dose confirmation 
study is to evaluate the safety, tolerability, and immunogenicity of messenger RNA (mRNA)-1893 
in adults aged 18 through 65 years living in endemic and non-endemic flavivirus areas. 
2.2. 
Background and Overview  
Zika virus (ZIKV) is a mosquito-borne and sexually transmitted single-stranded RNA virus of the 
Flaviviridae family, which includes yellow fever, dengue, West Nile, and Japanese encephalitis 
viruses. First discovered in 1947, ZIKV was recognized sporadically as a cause of mild, 
self-limited febrile illness in Africa and Southeast Asia. In 2007, an outbreak occurred on the North 
Pacific island of Yap, subsequently spreading through Oceana to re-emerge in 2013 and 2014 in 
an outbreak in French Polynesia before spreading to the Americas in 2015 (Duffy et al 2009; 
Derraik and Slaney 2015; Campos et al 2015). The outbreaks from 2015 onward have been of 
major public health concern due to their associated clinical complications such as Guillain-Barré 
syndrome in adults and a wide range of birth defects, including microcephaly, intrauterine growth 
restriction, and spontaneous abortion (Brasil et al 2016; Cao-Lormeau et al 2016). 
The devastating consequences of ZIKV infection led the World Health Organization (WHO) to 
declare a public health emergency of international concern on 01 Feb 2016 (Heymann et al 2016) 
and to call on the global research and development communities to prioritize the development of 
preventive and therapeutic solutions (WHO 2016a). Although the WHO declared an end to its 
global health emergency over the spread of ZIKV in November 2016, the long-term need for a 
ZIKV vaccine continues (WHO 2019) as a priority need under the Blueprint plan of action 
(WHO 2016b). 
Currently there is no approved vaccine to protect against ZIKV disease. 
To address the public health need, the Sponsor is developing mRNA-1893, a prophylactic vaccine 
against ZIKV. mRNA-1893 is a novel lipid nanoparticle (LNP)-encapsulated mRNA-based 
vaccine directed against the pre-membrane and envelope (prME) structural proteins of ZIKV. 
Following uptake of the LNP by the cell, the mRNA is translated and processed within the cytosol 
by the host cell, stimulating endogenous production of structurally intact protein antigens in a way 
that mimics wild-type viral infection and is able to induce highly targeted immune responses 
against infectious pathogens. Details on the mechanism of action and a summary of nonclinical 
studies of mRNA-1893 can be found in Section 2.2.1.  

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mRNA-1893 was tested in a Phase 1 clinical study (Study mRNA-1893-P101; NCT04064905) 
evaluating the safety and immunogenicity of 4 dose levels (
 µg) in a liquid 
formulation in approximately 100 healthy flavivirus-seronegative adults and 20 healthy flavivirus-
seropositive adults. The study was performed at 4 sites (3 in the continental United States [US] 
and 1 in Puerto Rico). Additional details on this clinical study and other clinical studies across the 
Sponsor’s infectious disease vaccine platform with mRNA vaccines using the same novel 
heptadecan-9-yl 8-((2-hydroxyethyl)(6-oxo-6(undecyloxy)hexyl)amino)octanoate 
(SM-102)-containing lipid formulation are described in Section 2.2.2. 
The Phase 2 Study mRNA-1893-P201 is intended to confirm the safety and immunogenicity trends 
observed during the Phase 1 study. Two dose levels and 2 dosing schedules of mRNA-1893 will 
be tested in this Phase 2 study for comparison to a placebo control. The 2 dose levels, 
 µg and 
 µg, will be compared for a 2-dose schedule, with doses 28 days apart. One single dose of the 
 µg-dose level will also be tested to explore its safety profile and characterize the intensity and 
persistence of the ZIKV-specific immune response. 
The Phase 2 primary study objectives will be the Day 57 assessment for humoral immunogenicity 
and safety with a planned study end date approximately 6 months after the last investigational 
product (IP) injection (Day 196) for all treatment arms. However, the study will be extended to 
approximately 24 months after the last IP injection for all participants who elect to enroll to assess 
the long-term safety of mRNA-1893, to assess the persistence of the ZIKV-specific immune 
response, and to capture the eventual occurrence of flavivirus infections. 
The Phase 2 study has already started to enroll participants; however, goals and treatment arms 
will not change with the current protocol amendment.  
The Phase 2 study will be conducted under US Investigational New Drug application in accordance 
with the protocol, International Council for Harmonization (ICH) Good Clinical Practice (GCP) 
guidelines, and applicable regulatory requirements. 
2.2.1. 
Nonclinical Studies 
In support of development of mRNA-1893 for prophylaxis against ZIKV infection, nonclinical 
immunogenicity, biodistribution, and safety studies have been completed with mRNA-1893 or 
similar mRNA-based vaccines formulated in SM-102-containing LNPs.  
In a non-Good Laboratory Practice (GLP) in vivo dose-range finding study, immunogenicity 
(binding antibody [bAb] and neutralizing antibody [nAb] titers) to the mRNA-1893 encoded 
protein was evaluated in female C57BL/6 mice at 4 doses 
 µg) following 
intramuscular (IM) injection on Days 1 and 29. mRNA-1893 generated strong nAb and bAb titers 
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at multiple doses. Mice dosed with 
 µg mRNA-1893 generated higher nAb and bAb titers 
than mice dosed with 
 µg mRNA-1893. Mice dosed with 
 µg mRNA-1893 
generated higher bAb titers compared with mice dosed with 
 µg mRNA-1893. 
The immunogenicity and efficacy of mRNA-1893 were evaluated in a non-GLP study in the rhesus 
macaque ZIKV infection model. A total of 40 monkeys were randomly assigned to 1 of 7 groups 
to receive mRNA-1893 
 µg), ZIKV purified inactivated vaccine (ZPIV 
[400 antigenic units]), a formalin-inactivated ZIKV strain PRVABC59 shown to be immunogenic 
in human, or buffer control. Dose administration occurred via IM injection on Day 0 and Day 28. 
Following blood collections on Day 56, animals were challenged by subcutaneous injection with 
a target dose of 1 × 105 plaque-forming units of ZIKV strain PRVABC59. Overall, administration 
of mRNA-1893 by IM injection (2 doses) was clinically well tolerated, with no 
mRNA-1893-related mortality, clinical observations, or changes in body weight. Animals in the 
buffer control group developed viremia that persisted for 3 to 7 days, whereas mRNA-1893- and 
ZPIV-treated animals were either negative for ZIKV RNA at all time points evaluated or had 
sporadic instances of low levels of ZIKV RNA at a single time point after ZIKV challenge. 
Detection of ZIKV RNA was inversely related to detection of ZIKV nAbs prior to ZIKV challenge. 
mRNA-1893– and/or ZPIV-treated animals had detectable nAb titers in the ZIKV 
microneutralization (MN) assay at Days 28 and 56 as well as at the End of Study (EOS) (Day 77, 
21 days after ZIKV challenge), whereas animals in the buffer control group did not have 
ZIKV-neutralizing titers until after ZIKV challenge on Day 77. 
Overall, these results demonstrate that mRNA-1893 generates strong immunogenic response in 
mice and non-human primates and prevents viremia, with either no or low levels of ZIKV RNA 
upon challenge in the rhesus macaque ZIKV infection model. 
To evaluate the generalized tissue distribution and tissue half-life of mRNA-1893, the 
biodistribution of mRNA-1647, a similar mRNA-based vaccine formulated in SM-102-containing 
LNPs, was evaluated in male rats. mRNA-1647 is a novel mRNA-based cytomegalovirus (CMV) 
vaccine formulated in a mixture of the same 4 lipids as mRNA-1893. The biodistribution of 
mRNA-based vaccines formulated in LNPs is predicted to be driven by the LNP characteristics. 
Therefore, mRNAs that are within an LNP of the same composition (eg, mRNA-1893 and 
mRNA-1647) are expected to distribute similarly. Overall, only a relatively small fraction of the 
administered mRNA-1647 dose distributed to distant tissues, and the mRNA constructs did not 
persist past 1 to 3 days in tissues other than the vaccination site, lymph nodes, and spleen.  
The safety and tolerability of 3 dose levels of mRNA-1893 administered by IM injection were 
evaluated in a GLP-compliant, repeat dose (1 month; 3 doses) toxicity study in Sprague Dawley 
rats followed by a 2-week recovery period. Animals were administered mRNA-1893 at doses of 
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 µg/dose or phosphate buffered saline via IM injection on Days 1, 15, and 29. The 
results of this study indicated that administration of mRNA-1893 was clinically tolerated in rats 
up to 
 μg/dose with no mortality or changes in body weight or food consumption. Starting at 
 μg/dose, dose-dependent clinical signs (swelling/firmness/redness/scabs) at the injection site, 
changes in clinical pathology parameters and cytokines concentrations, and an increase in body 
temperature were observed and were consistent with an inflammatory reaction. Dose-dependent 
effects were observed at the vaccination site, spleen, liver, and seminal vesicle of animals given 
mRNA-1893. Additional microscopic findings in the iliac, inguinal, and popliteal lymph nodes or 
their perinodal tissue; perineural tissue of the sciatic nerve; spleen (extramedullary hematopoiesis); 
and bone marrow of animals given mRNA-1893 were considered to be an extension, a secondary 
response, or a reactive response to the vaccination site inflammation. At the end of the 2-week 
recovery period, all changes were partially or fully recovered.  
In GLP-compliant studies, SM-102, the novel lipid component of the LNP formulation, was not 
genotoxic when tested in a bacterial reverse mutation (Ames) test or an in vitro micronucleus test. 
An in vivo micronucleus study in Sprague Dawley rats showed that a similar mRNA-based vaccine 
formulated in SM-102 containing LNPs (mRNA-1706, which encodes the ZIKV prME 
polypeptide [different from the sequence encoded in mRNA-1893]), induced statistically 
significant increases in micronucleated immature erythrocytes in male rats at both 24 and 48 hours 
and in female rats at 48 hours only; however, there was no clear dose response, and the increases 
were generally weak and associated with minimal bone marrow toxicity. These observations 
indicate that the risk to humans after IM administration is low due to minimal systemic exposure.  
A detailed review of nonclinical experience with mRNA-1893 is provided in the Investigator’s 
Brochure (IB). 
2.2.2. 
Clinical Studies 
mRNA-1893 was tested in a Phase 1 clinical study (Study mRNA-1893-P101; NCT04064905) 
evaluating the safety and immunogenicity of 4 dose levels 
 µg) in a liquid 
formulation in approximately a total of 120 participants aged 18 through 49 years (
 per dose 
level with 25 baseline flavivirus-seronegative and 5 flavivirus-seropositive participants). The 
study was performed at 4 sites (3 in the continental US and 1 in Puerto Rico). Group unblinding 
interim analyses performed at Day 57 (ie, 28 days after the second vaccine administration of the 
 µg dose levels) showed a safety profile compatible with a large use of the 
vaccine candidate and a production of ZIKV-specific nAbs, as measured by plaque reduction 
neutralization test (PRNT), at a seroconversion rate (SCR) of 86.4% (65.1% - 97.1%) at 
 µg 
dose level, 95.5% (77.2% - 99.9%) at 
 µg dose level, 100% (85.8% - 100%) at 
 µg dose 
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level, and 95.7% (78.1% - 99.9%) at 
 µg dose level 28 days after the last vaccine 
administration. Clinical study report (CSR) writing corresponding to the safety and 
immunogenicity evaluations performed at Month 6 and Month 13 is under preparation.  
The Sponsor has demonstrated several mRNA vaccines to confer protection against a variety of 
pathogens in addition to Zika virus, including SARS-CoV-2, influenza virus, and chikungunya 
virus, in a variety of animal species such as mice, rats, cotton rats, ferrets, and non-human primates. 
As of February 2021, mRNA vaccines with SM-102-containing lipid formulations are currently 
being evaluated for infectious disease indications including: prophylactic protection against 
coronavirus disease 2019 (COVID-19) caused by the SARS-CoV-2 virus (NCT04470427, 
NCT04649151, NCT04405076, NCT04283461), human CMV (NCT03382405, NCT04232280), 
human 
metapneumovirus/parainfluenza 
virus 
Type 
3 
(hMPV/PIV3; 
NCT04144348, 
NCT03392389), 
respiratory 
syncytial 
virus 
(RSV; 
NCT04528719), 
influenza 
virus 
(NCT04956575), and Zika virus (NCT04064905) infections. The Sponsor’s COVID-19 vaccine 
received authorization in the US for emergency use to prevent COVID-19 infections in adults on 
18 Dec 2020. 
A detailed review of clinical experience with LNPs containing SM-102 (mRNA vaccines and 
placebo) is provided in the IB. 
2.3. 
Benefit/Risk Assessment 
Approximately 600 participants will be exposed to mRNA-1893 in this study; approximately 
200 participants will receive placebo. 
A summary of the potential risks and benefits of mRNA-1893 is provided in the current IB. 
2.3.1. 
Known Potential Benefits 
Participants who receive mRNA-1893 may or may not directly benefit from vaccination as the 
protective efficacy of mRNA-1893 has yet to be established. 
Participants can obtain medical advice about their general health status through the medical 
evaluations/assessments associated with this study. 
Participants will be contributing to the process of developing a new potentially prophylactic 
measure against ZIKV in an area of unmet medical need, should ZIKV epidemics re-emerge. 
2.3.2. 
Anticipated Risks  
As with all injectable vaccines, immediate systemic allergic reactions, including anaphylaxis, to 
vaccination can occur. These reactions are very rare and are estimated to occur once per 450,000 
vaccinations for vaccines that do not contain allergens such as gelatin or egg protein 
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(Zent et al 2002). As a precautionary measure, all participants will remain under observation at the 
study site for safety monitoring for at least 30 minutes after IP injection. Vasovagal syncope 
(fainting) can occur before or after any IP injection, is usually triggered by the pain or anxiety 
caused by the injection, and is not related to the substance injected. Therefore, it is important that 
standard precautions and procedures be followed to avoid injury from fainting. Intramuscular 
vaccination commonly precipitates a transient and self-limiting local inflammatory reaction. This 
typically includes pain, erythema (redness), or swelling/induration (hardness) at the injection site. 
Most systemic adverse events (AEs) observed after IP injection do not exceed mild to moderate 
severity and are of short duration.  
In Study mRNA-1893-P101 that tested dose levels from 
 to 
 µg, interim safety analyses after 
28 days after the last vaccination have been performed. All dose levels were generally well 
tolerated. However, there was a trend towards more observations of local erythema and 
swelling/induration at the injection site with higher dose levels and this was evident at the 
 µg 
dose level, in particular after the second vaccine administration. More solicited systemic ARs were 
noted at the 
 µg dose level in terms of myalgia, fatigue, headache, chills, fever, and nausea 
with higher grade intensity. With the acknowledgment that the sample size of seropositive 
participants was very limited, the baseline flavivirus positive serostatus did not seem to negatively 
affect the safety profile. No serious adverse event (SAE) and no AEs of special interest related to 
mRNA-1893 were reported at any dose levels. 
Regarding the 
 µg and 
 µg dose levels tested in the mRNA-1893-P101 study, ie, the same 
dose levels planned to be tested in the Phase 2 study, the most commonly reported solicited 
systemic adverse reactions (ARs) were: respectively for 
 µg and 
 µg, after the first vaccine 
administration, headache (21.7% and 12.5%), fatigue (21.7% and 12.5%), myalgia (13% and 
4.2%), and nausea (8.7% and 12.5%); and after the second administration, fatigue (45.5% and 
41.7%), headache (36.4% and 37.5%), chills (22.7% and 45.8%), myalgia (18.2% and 41.7%), and 
arthralgia (18.2% and 37.5%). Fever was reported in 4.2% of the participants at the 
 µg dose 
level after the first vaccine administration corresponding to a Grade 1 intensity in 1 participant, 
and in 29.2% of participants (7 cases) after the second vaccine administration; among those 7 
cases, 2 were of Grade 3 intensity. With the 
 µg dose level, no participant reported fever after 
the first vaccine administration and 12.6% (3 cases) reported fever of mild or moderate intensity 
after the second vaccine administration; no fever of Grade 3 was observed. As the dose levels 
selected for Study mRNA-1893-P201 have been already tested with the same liquid formulation 
as those used in mRNA-1893-P101, a similar safety profile as the one observed in the Phase 1 
study is anticipated.  
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Laboratory abnormalities (including increases in liver enzymes and in coagulation parameters) 
following vaccine administrations were observed in clinical studies performed by the Sponsor with 
mRNA-based vaccine candidates. These abnormalities were without clinical symptoms or signs 
associated and returned toward baseline (Day 1) values over time; the clinical significance of these 
observations is unknown. In Study mRNA-1893-P101, inclusion criteria required that all 
participants had Grade 0 laboratory test results at enrollment. Post-vaccination laboratory 
abnormalities were infrequent, mostly Grade 1 or Grade 2, except 1 case of Grade 4 prothrombin 
test increase at Day 29 at the 
 µg dose level, not related to the vaccination, and further attributed 
to a laboratory technical issue. None of those laboratory abnormalities were considered clinically 
relevant. Further details are provided in the current IB.  
There is a theoretical risk that active vaccination to prevent novel viral infection may cause a 
paradoxical increase in the risk of disease. This possibility is based on the rare phenomenon of 
vaccine-associated disease enhancement, which was first seen in the 1960s with 2 vaccines made 
in the same way (formalin-inactivated whole virus) and designed to protect children against 
infection with respiratory syncytial virus (Chin et al 1969) or measles (Fulginiti et al 1967). 
Antibody disease enhancement has also been proposed as a possible explanation for the cases of 
more serious disease associated with dengue vaccination (Thomas and Yoon 2019; WHO 2018); 
this phenomenon was already known in cases of a dengue reinfection caused by a heterologous 
serotype. It is not known if mRNA-1893 will increase the risk of ZIKV-enhanced disease and also 
the risk of dengue-virus–enhanced disease because of the close relationship between dengue virus 
and ZIKV (flavivirus family, geographic location, cross-reactivity). To monitor this risk, the 
Sponsor will perform a careful safety follow-up throughout the entire study duration by 
establishing an Oversight Safety Team (OST) and an independent Data Safety Monitoring Board 
(DSMB). The OST will perform a biweekly review of safety events in a blinded fashion. In 
addition, the DSMB will convene on an approximately quarterly basis until study end and at any 
time if there is an ad-hoc safety concern detected by the OST. The DSMB will review unblinded 
study data to evaluate the safety findings. All AEs, SAEs, and medically attended AEs (MAAEs) 
will be reviewed in terms of frequency and severity by the board and they will be asked to provide 
recommendations and guidance as to management of safety follow-up within the study 
(Section 11.1.1) 
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. The risk is highest in males under the age of 40 years, 
specifically males between 12 through 17 years. Symptoms include chest pain, shortness of breath, 
or palpitations. Study participants should seek medical attention and also notify study site staff if 
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any of these symptoms occur following vaccination. While some cases required intensive care 
support, available data from short-term follow-up suggest that most individuals have had 
resolution of symptoms with conservative management. It is not known whether the risk of 
myocarditis or pericarditis is increased following additional doses of the vaccine. 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 
Appropriate eligibility criteria, as well as clearly defined study procedures, are included in this 
protocol. The risk to participants in this study may be minimized by compliance with the eligibility 
criteria and study procedures. 
All safety findings will be closely monitored biweekly by the OST and reviewed by the 
independent DSMB during periodic meetings to evaluate the safety and treatment status of all 
participants. The composition, roles, responsibilities, and governance of the OST and DSMB will 
be described in separate charters. 
Considering the safety profile observed in Study mRNA-1893-P101 and the measures taken to 
minimize the risk to study participants, the potential risks are balanced by the anticipated benefits 
that may be afforded through vaccination with mRNA-1893.  

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3. 
OBJECTIVES AND ENDPOINTS  
3.1. 
Primary Objectives and Endpoints 
Table 3: Primary Objectives and Endpoints 
Objectives 
Endpoints 
Primary Safety 
 
To evaluate the safety, tolerability, and 
reactogenicity of 2 dose levels of 
mRNA-1893 Zika vaccine, administered in a 
1-dose (
 µg) or 2-dose schedule (
 µg or 
 µg dose level) given 28 days apart, in 
comparison to a placebo control. 
• 
Solicited local and systemic ARs through 7 days after each 
IP injection. 
• 
Unsolicited AEs through 28 days after each IP injection.  
• 
MAAEs throughout the entire study period. 
• 
SAEs and AESIs throughout the entire study period. 
Primary Immunogenicity 
 
To evaluate the immunogenicity of 2 dose 
levels of mRNA-1893 Zika vaccine, 
administered in a 1-dose (
 µg) or 2-dose 
schedule (
 µg or 
 µg dose level) given 
28 days apart, as measured by ZIKV-specific 
neutralization assay (PRNT), in comparison to 
a placebo control at Day 57. 
• 
GMT of ZIKV-specific nAbs at Day 57, as measured by 
PRNT in all participants, in initially 
flavivirus-seronegative, and in initially 
flavivirus-seropositive participants. 
• 
Seroconversion from Day 1 to Day 57. 
Abbreviations: AE = adverse event; AESIs = adverse events of special interest; AR = adverse reaction; GMT = geometric mean 
titer; LLOQ = lower limit of quantification; MAAE = medically attended adverse event; nAb = neutralizing antibody; PRNT = 
plaque reduction neutralization test; SAE = serious adverse event; ZIKV = Zika virus. 
Note: Seroconversion is defined as either an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or 
above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers (as measured 
by PRNT). 
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3.2. 
Secondary Objectives and Endpoints 
Table 4: Secondary Objectives and Endpoints  
Objectives 
Endpoints 
Secondary Immunogenicity 
 
To evaluate the immunogenicity of 2 dose 
levels of mRNA-1893, as measured by 
ZIKV-specific neutralization assay (PRNT 
and MN), in comparison to a placebo control, 
in flavivirus-seronegative participants at 
baseline and in flavivirus-seropositive 
participants at baseline. 
• 
GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, and 57 
(Day 57 only for MN), as measured by PRNT and MN. 
• 
GMT of ZIKV-specific nAbs in initially 
flavivirus-seronegative participants at Days 1, 8, 29, 36, 
and 57 (Day 57 only for MN), as measured by PRNT and 
MN. 
• 
GMT of ZIKV-specific nAbs in initially 
flavivirus-seropositive participants at Days 1, 8, 29, 36 and 
57 (Day 57 only for MN), as measured by PRNT and MN. 
• 
GMFR of ZIKV-specific nAbs in all participants, in 
initially flavivirus-seronegative and in initially flavivirus-
seropositive participants at Days 8, 29, 36, and 57, as 
measured by PRNT and MN. 
• 
Seroconversion from Day 1 (baseline) to Days 8, 29, 36, 
and 57 (Day 57 only for MN), as measured by PRNT and 
MN. 
• 
Seroresponse at Days 8, 29, 36, and 57 (Day 57 only for 
MN) in flavivirus-seronegative participants at baseline. 
• 
Increase from baseline of 2-fold or 4-fold in ZIKV-specific 
nAb titers at Days 8, 29, 36 and 57, as measured by PRNT 
and MN, in flavivirus-seropositive participants at baseline. 
Abbreviations: GMFR = geometric mean fold rise; GMT = geometric mean titer; LLOQ = lower limit of quantification; 
MN = microneutralization; nAb = neutralizing antibody; PRNT = plaque reduction neutralization test; ZIKV = Zika virus. 
Notes: Seroconversion is defined as either an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or 
above LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers (as measured 
by PRNT or MN). 
Seroresponse is defined as an increase in ZIKV-specific nAb titer from below the LLOQ to greater than or equal to the LLOQ (as 
measured by PRNT or MN). 
 

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3.3. 
Exploratory Objectives and Endpoints 
Table 5: Exploratory Objectives and Endpoints 
Objectives 
Endpoints 
Exploratory 
 
To evaluate the duration of the humoral 
immune response of 2 dose levels of 
mRNA-1893 at Days 85, 196, 364, 532, and 
700, as measured by ZIKV-specific 
neutralization assays (PRNT and MN), in 
comparison to a placebo control, in flavivirus-
seronegative participants at baseline and in 
flavivirus-seropositive participants at 
baseline. 
• GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 
700, as measured by PRNT and MN. 
• GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 
700, as measured by PRNT and MN, in 
flavivirus-seronegative participants at baseline.  
• GMT of ZIKV-specific nAbs at Days 85, 196, 364, 532, and 
700, as measured by PRNT and MN, in flavivirus-seropositive 
participants at baseline.  
• GMFR of ZIKV-specific nAbs in all participants, in initially 
flavivirus-seronegative, and in initially flavivirus-seropositive 
participants at Day 85, 196, 364, 532, and 700, as measured 
by PRNT and MN. 
• Seroconversion1 from Day 1 (baseline) to Days 85, 196, 364, 
532, and 700, as measured by PRNT and MN. 
• Seroresponse2 at Days 85, 196, 364, 532, and 700, as 
measured by PRNT and MN, in flavivirus-seronegative 
participants at baseline.  
• Increase from baseline of 2-fold or 4-fold in ZIKV-specific 
nAb titers at Days 85, 196, 364, 532, and 700, as measured by 
PRNT and MN, in flavivirus-seropositive participants at 
baseline.  
• Proportion of all participants, of baseline 
flavivirus-seronegative participants, and of baseline 
flavivirus-seropositive participants with a ZIKV-specific nAb 
titer equal or greater than a nAb titer defined as a protective 
level in an animal model, at baseline, and Days 8, 29, 36, 57, 
85, 196, 364, 532, and 700, as measured by PRNT. 
• Proportion of all participants, of baseline 
flavivirus-seronegative participants, and of baseline 
flavivirus-seropositive participants with a ZIKV-specific nAb 
titer equal or greater than a nAb titer defined as a protective 
level in an animal model, at baseline, and Days 8, 29, 36, 57, 
85, 196, 364, 532, and 700, as measured by MN. 

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Objectives 
Endpoints 
Exploratory 
 
To evaluate the humoral immunogenicity of 
2 dose levels of mRNA-1893, as measured by 
RVP and by ligand binding assay, in 
comparison to a placebo control, in 
flavivirus-seronegative participants at baseline 
and in flavivirus-seropositive participants at 
baseline. 
• GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by RVP.  
• GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by RVP, in 
flavivirus-seronegative participants at baseline.  
• GMT of ZIKV-specific nAbs at Days 1, 8, 29, 36, 57, 85, 196, 
364, 532, and 700, as measured by RVP, in 
flavivirus-seropositive participants at baseline.  
• Seroconversion1 from Day 1 (baseline) to Days 8, 29, 36, 57, 
85, 196, 364, 532, and 700, as measured by RVP. 
• Seroresponse2 at Days 8, 29, 36, 57, 85, 196, 364, 532, and 
700, as measured by RVP, in flavivirus-seronegative 
participants at baseline.  
• Increase from baseline of 2-fold or 4-fold in ZIKV-specific 
nAb titers at Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as 
measured by RVP, in flavivirus-seropositive participants at 
baseline. 
• GMC of ZIKV-specific serum ligand bAbs at Days 1, 8, 29, 
36, 57, 85, 196, 364, 532, and 700, as measured by ligand 
binding assay. 
• GMC of ZIKV-specific bAbs at Days 1, 8, 29, 36, 57, 85, 
196, 364, 532, and 700, as measured by ligand binding assay, 
in flavivirus-seronegative participants at baseline. 
• GMC of ZIKV-specific bAbs at Days 1, 8, 29, 36, 57, 85, 
196, 364, 532, and 700, as measured by ligand binding assay, 
in flavivirus-seropositive participants at baseline. 
• Seroconversion3 from Day 1 (baseline) to Days 8, 29, 36, 57, 
85, 196, 364, 532, and 700, as measured by ligand binding 
assay. 
• Seroresponse4 at Days 8, 29, 36, 57, 85, 196, 364, 532, and 
700, as measured by ligand binding assay, in flavivirus-
seronegative participants at baseline. 
• Increase from baseline 2-fold or 4-fold in bAb concentrations 
at Days 8, 29, 36, 57, 85, 196, 364, 532, and 700, as measured 
by ligand binding assay, in flavivirus-seropositive participants 
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Objectives 
Endpoints 
Exploratory 
 
To evaluate the ZIKV-specific cellular 
immune response of 2 dose levels of 
mRNA-1893 in comparison to a placebo 
control in flavivirus-seronegative participants 
at baseline and in flavivirus-seropositive 
participants at baseline (CMI subset of 
participants). 
• Frequency of ZIKV-specific T cells at Days 1 (baseline), 29, 
36, 57, 196, 364, 532, and 700, as measured by intracellular 
cytokine staining assay and sequencing (CMI subset of 
baseline flavivirus-seronegative and -seropositive 
participants).  
• Frequency of ZIKV-specific B cells at Days 1 (baseline), 29, 
36, 57, 196, 364, 532, and 700, as measured by ELISpot (CMI 
subset of baseline flavivirus-seronegative and -seropositive 
participants). 
• Additional assays to profile the T- and B-cell responses may 
also be included (CMI subset of baseline 
flavivirus-seronegative and -seropositive participants). 
To assess the occurrence of flavivirus 
infections throughout the entire course of 
participation in the study in comparison to a 
placebo control. 
• GMC of NS1-specific serum bAbs at Days 1 (baseline), 85, 
196, 364, 532, and 700, as measured by ELISA.  
• Seroconversion5 (NS1-specific bAbs) from Day 1 (baseline) 
to Days 85, 196, 364, 532, and 700. 
Abbreviations: bAb = binding antibody; CMI = cell-mediated immunity; ELISA = enzyme-linked immunosorbent assay; 
ELISpot = enzyme-linked immunosorbent spot; GMFR = geometric mean fold rise; GMT = geometric mean titer; 
GMC = geometric mean concentration; LLOQ = lower limit of quantification; MN = microneutralization; nAb = neutralizing 
antibody; NS1 = nonstructural protein 1; PRNT = plaque reduction neutralization test; RVP = reporter virus particle; 
ZIKV = Zika virus. 
1 
Seroconversion is defined as either an increase in ZIKV-specific nAb titer from below the LLOQ to a titer equal to or above 
LLOQ, or an increase of at least 4-fold in ZIKV-specific nAb titer in participants with pre-existing nAb titers (as measured 
by PRNT, MN, or RVP). 
2 
Seroresponse is defined as an increase in ZIKV-specific nAb titer from below the LLOQ to greater than or equal to the 
LLOQ (as measured by PRNT, MN, or RVP). 
3 
Seroconversion is defined as either an increase in ZIKV-specific bAb concentration from below the LLOQ to a 
concentration equal to or above LLOQ, or an increase of at least 4-fold in ZIKV-specific bAb concentration in participants 
with pre-existing bAb concentrations (as measured by ligand binding assay). 
4 
Seroresponse is defined as an increase in ZIKV-specific bAb concentration from below the LLOQ to greater than or equal to 
the LLOQ (as measured by ligand binding assay). 
5 
Seroconversion is defined as an increase in NS1-specific bAb concentration from below the LLOQ to a concentration equal 
to or above the LLOQ, or an increase of at least 4-fold in NS1-specific bAb concentration as measured by ELISA. 
 

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4. 
STUDY DESIGN  
4.1. 
General Design 
This is a Phase 2, randomized, observer-blind, placebo-controlled, dose confirmation study.  
All participants will be evaluated for their eligibility (Section 4.1.1) for enrollment in the 
Vaccination Period and will be followed for approximately 6 months (Day 196) after their last IP 
injection (Section 4.1.2). Table 1 displays the Schedule of Assessments (SOA) for all participants 
through Day 196. All participants in all treatment arms will have the opportunity to continue to be 
followed as part of an approximately 24-month Extension Period (through Day 700) after their last 
IP injection (Section 4.1.3). Table 2 displays the SOA for participants who continue into the 
Extension Period through Day 700. The study design is illustrated in Figure 1. 
A total of approximately 800 participants will be randomly assigned to receive either 
 µg or 
 µg mRNA-1893 administered as a 2-dose regimen with at least a 28-day interval between 
vaccinations (Treatment Arm A or Treatment Arm B), or 
 µg mRNA-1893 administered as a 
1-dose regimen (Treatment Arm C), or placebo control administered as a 2-dose regimen with at 
least a 28-day interval between doses (Treatment Arm D) according to a 1:1:1:1 randomization 
ratio (ie, 200 participants per treatment arm with approximately 100 participants per baseline 
flavivirus serostatus in each treatment arm). Randomization was stratified by participants’ baseline 
flavivirus serostatus assessed by a rapid dengue point-of-care test on site in the original protocol 
(dated 21 Feb 2021). Under the current protocol amendment, randomization will be stratified only 
by participants’ region (continental US and Puerto Rico). All treatment arms will be enrolled in 
parallel. In order to maintain the blinding and to have the same study evaluation time point with 
both mRNA-1893 dose regimens relative to the last IP injection, participants randomly assigned 
to Treatment Arm C will be administered placebo at Day 1 and mRNA-1893 at Day 29 (Table 6).  
Table 6: Treatment Arms 
 
Study Day 
Day 1 
Day 29 
Treatment Arm A 
mRNA-1893 
 µg  
First vaccination 
mRNA-1893 
 µg  
Second vaccination 
Treatment Arm B 
mRNA-1893 
 µg  
First vaccination 
mRNA-1893 
 µg  
Second vaccination 
Treatment Arm C 
Placebo 
mRNA-1893 
 µg  
First vaccination 
Treatment Arm D 
Placebo 
Placebo 
 
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All participants will have up to 8 clinic visits (Days 0 [Eligibility Visit], 1 (baseline), 8, 29, 36, 57, 
85, and 196) and 3 safety telephone calls (Days 112, 140, and 168). Participants who continue into 
the Extension Period will have 3 additional clinic visits at Days 364, 532, and 700. 
The EOS is defined in Section 4.6. Participants who withdraw from further IP injection for any 
reason after their first IP injection but do not withdraw consent will complete all study procedures 
through the EOS Visit (Section 7). 
4.1.1. 
Eligibility Evaluation 
Up to 8 days prior to Visit 1 (Day 1), potential participants will be evaluated (interview and 
physical examination) to determine their eligibility to participate in the study according to the 
inclusion and exclusion criteria (Section 5.1 and Section 5.2, respectively). The Eligibility (Day 0) 
and Baseline (Day 1) Visits may be combined on the same day. 
4.1.2. 
Vaccination Period  
All participants will receive IP injections at Visit 1 (Day 1) and Visit 3 (Day 29). Participants will 
be asked to complete an electronic diary (eDiary) to monitor solicited ARs for 6 days after each 
IP injection (Days 1 through 7 and Days 29 through 35) and to monitor unsolicited AEs for 28 
days after each IP injection (Days 1 through 57). Serious AEs, AESIs and MAAEs will be 
monitored from Day 1 for approximately 6 months (Visit 10 [Day 196]) after the last IP injection.  
Blood samples will be collected from all participants at Days 1 (baseline), 8, 29, 36, 57, 85, and 
196 for the assessment of antibody-mediated immunogenicity. Blood samples will be collected 
from a subset of participants (cell-mediated immunity [CMI] subset) at Days 1 (baseline), 29, 36, 
57, and 196 for peripheral blood mononuclear cell (PBMC) collection and assessment of cellular 
immunity. Blood samples collected from all participants at Days 85 and 196 will be used for 
detection of asymptomatic flavivirus infections. 
In case of signs or symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas 
where the study will be performed), an additional blood sample will be collected to confirm the 
diagnosis via specific serology and reverse transcriptase polymerase chain reaction (RT-PCR), and 
clinical information will be carefully collected to evaluate the severity of the clinical case. Those 
symptoms are not specific; however, an association of acute fever onset with maculopapular rash, 
arthralgia, and conjunctivitis during the seasonal circulation of mosquitos must trigger samplings. 
Also, special attention will be paid to the reporting of neurological signs or symptoms evoking 
Guillain-Barré syndrome. 

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4.1.3. 
Extension Period 
All participants enrolled who consent to continue into the Extension Period will return to the clinic 
for follow-up visits approximately every 6 months after the last IP injection (Days 364, 532, and 
700). Serious AEs, AESIs, and MAAEs will be monitored throughout the Extension Period. 
Blood samples will be collected at Days 364, 532, and 700 for the assessment of antibody-mediated 
immunogenicity. Blood samples will be collected from the CMI subset participants at Days 364, 
532, and 700 for PBMC collection and assessment of cellular immunity. Blood samples collected 
from all participants at Days 364, 532, and 700 will be used for detection of asymptomatic 
flavivirus infections. Additional blood samples might also be collected during unscheduled visits 
for safety and/or immunogenicity purposes, at the discretion of the investigator. 
As previously described in Section 4.1.2, in case of signs or symptoms suggesting a flavivirus 
infection (mostly dengue and Zika in the areas where the study will be performed) during the 
Extension Period, an additional blood sample will be collected to confirm the diagnosis via specific 
serology and RT-PCR, and clinical information will be carefully collected to evaluate the severity 
of the clinical case. Also, special attention will be paid to collect signs or symptoms possibly 
related to Guillain-Barré syndrome. 
4.2. 
Scientific Rationale for Study Design 
The design and dose levels proposed for this study (Study mRNA-1893-P201) are based on 
accumulated safety and immunogenicity data from the Phase 1 Study mRNA-1893-P101, which 
involved a total of 120 participants. Group unblinding interim analyses performed at Day 57 (ie, 
28 days after the second vaccination) showed a safety profile compatible with a large use of the 
vaccine candidate and a production of ZIKV-specific nAbs at an SCR ranging from 12.5% 
(2.7% - 32.4%) to 75% (53.3% - 90.2%) after 1 vaccine administration and from 86.4% 
(65.1% - 97.1%) to 100% (85.8% - 100%) after the complete 2-dose vaccine administration. 
Study mRNA-1893-P201 is intended to confirm the safety and immunogenicity trends observed 
during the Phase 1 study and aims to select the dose level for the Phase 3 program. Two dose 
levels, 
 µg and 
 µg, have been chosen as they appear to give the optimal response at Day 57 
in terms of geometric mean titers (GMTs) and SCRs with a similar safety profile. The number of 
participants (200 per treatment arm with approximately 100 participants per baseline flavivirus 
serostatus in each treatment arm) planned for enrollment is consistent with a Phase 2 stage clinical 
study. The collection of solicited ARs and unsolicited AEs following vaccination is consistent with 
vaccine evaluation studies. Additionally, the 2-year follow-up will provide long-term safety profile 
information and documentation on the duration of the ZIKV-specific nAb response after a 1- or 2-
dose regimen. It may also give the opportunity to evaluate occurrence of flavivirus infections, 
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mostly ZIKV and dengue, as the excontinental US sites are areas with potential for flavivirus 
circulation. The collection of blood at the given time points and the selection of the assays for the 
assessment of the ZIKV-specific immune response are based on experience from the preclinical 
and previous clinical studies.  
4.3. 
Justification for the Choice of Study Population 
It is anticipated that the specific immune response to a ZIKV vaccine candidate in participants who 
are baseline seronegative may be different from responses in those who are baseline seropositive 
for flavivirus. To explore the potential differences in safety and immunogenicity, this study will 
enroll healthy flavivirus-seronegative and flavivirus-seropositive participants. 
Safety and immunogenicity evaluation in adults who are flavivirus seronegative at baseline and 
the most critical at risk population will confirm appropriateness of the dose selection in a larger 
number of participants.  
As the Phase 1 study was predominantly performed in initially flavivirus-seronegative 
participants, this Phase 2 study will expand the safety data available in flavivirus-seropositive 
participants, in order to have enough confidence to administer mRNA-1893 without flavivirus 
serological knowledge in the large Phase 3 studies.  
This Phase 2 study population will also target the age group in which the majority of cases occurred 
in previous epidemics (18 to 49 years of age) and a slightly older population extending up to 
65 years, to account for the case distribution age for neurological sequalae such as Guillain-Barré 
syndrome that has been described with ZIKV. 
4.4. 
Justification for Dose and Schedule 
The 2 dose levels of mRNA-1893 tested in participants will be 
 μg and 
 μg based on the 
assessment of available safety and immunogenicity data from Study mRNA-1893-P101. The 
2 dose levels will be administered as a 2-dose regimen (Treatment Arm A and B) with at least a 
28-day interval between vaccinations that seems to give the optimal response. In addition, the 
-µg dose will be administered as a single-dose regimen (Treatment Arm C) to generate safety 
and immunogenicity data that could be valuable in emergency situations, in military personnel and 
traveler populations who might need a rapid response, and also in populations living in endemic 
areas and with pre-existing immune response for which 1 vaccine administration might be 
sufficient. 
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4.5. 
Justification for the Use of Placebo 
Because there are currently no licensed ZIKV vaccines available to be used as reference vaccine, 
0.9% sodium chloride solution for injection (United States Pharmacopeia [USP] or British 
Pharmacopeia [BP]) (normal saline) will be used as placebo to maintain the blinding of the study 
and to serve as a control for the safety and immunogenicity assessments.  
Moreover, to have the same study evaluation time point for primary evaluation with both 
mRNA-1893 dose regimens relative to the last IP injection, participants randomly assigned to 
Treatment Arm C will be injected at Day 1 with placebo and will receive mRNA-1893 at Day 29 
(Table 6). 
Those participants who receive saline placebo will have the same safety follow-up as those who 
receive the 1-dose or 2-dose mRNA-1893 regimen (Treatment Arm A and Treatment Arm B). 
4.6. 
End of Study Definition 
The EOS is defined as completion of the last visit of the last participant in the study or last 
scheduled procedure as shown in Table 1 and Table 2 for the last participant in the study globally. 
Participants who do not consent to continue into the Extension Period will be considered to have 
completed the study if they have completed the EOS Visit approximately 6 months (Visit 10 
[Day 196]) after the last IP injection. Participants who consent to continue into the Extension 
Period will be considered to have completed the study if they have completed the EOS Visit 
approximately 24 months (Day 700) after the last IP injection. 

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5. 
STUDY POPULATION 
The study will enroll approximately 800 adult participants aged 18 through 65 years at baseline, 
including approximately 400 flavivirus-seropositive participants and 400 flavivirus-seronegative 
participants, who will receive mRNA-1893 or placebo.  
A dengue rapid point-of-care test initially used to stratify study participants has been discontinued. 
After this protocol amendment, all participants will be stratified based on geographic region, 
assuming most of the baseline seronegatives will come from continental US sites and the baseline 
seropositives from Puerto Rico. The confirmation will be done based on flavivirus serology testing 
(dengue immunoglobulin G [IgG] and immunoglobulin M [IgM], West Nile IgG and IgM) 
performed on a blood sample collected prior to administration of the first vaccination with a goal 
of an approximately equal distribution of participants among seronegative and seropositive 
participants within each treatment group. 
The planned participant distribution is presented by treatment arm in Table 7. 
Table 7: Participant Distribution by Treatment Arm 
Investigational Product 
Baseline 
Flavivirus-Seronegative 
Participants 
Baseline 
Flavivirus-Seropositive 
Participants 
Total 
mRNA-1893 
 µg 
(Treatment Arm A) 
100 
100 
200 
mRNA-1893 
 µg 
(Treatment Arm B) 
100 
100 
200 
mRNA-1893 
 µg  
(Treatment Arm C) 
100 
100 
200 
Placebo 
(Treatment Arm D) 
100 
100 
200 
Total 
400 
400 
800 
 
Upon completion of 
all eligibility evaluations, the 
investigator 
will review the 
inclusion/exclusion criteria for each participant to determine if the participant is eligible for 
enrollment in the study. Participants who meet all eligibility criteria will be enrolled in the study.  
5.1. 
Inclusion Criteria  
Participants are eligible to be included in the study only if all the following criteria apply: 
1. Male or female participant aged 18 through 65 years at the time of consent. 
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2. Understands and agrees to comply with the study procedures and provides written informed 
consent. 
3. According to investigator assessment, is in good general health and can comply with study 
procedures. 
4. Female participants of nonchildbearing potential may be enrolled in the study. 
Nonchildbearing potential is defined as surgically sterile (history of bilateral tubal ligation, 
bilateral oophorectomy, hysterectomy) or postmenopausal (defined as amenorrhea for 
≥ 12 consecutive months prior to the eligibility evaluation without an alternative medical 
cause). The follicle-stimulating hormone (FSH) level may be measured at the discretion of 
the investigator to confirm postmenopausal status. 
5. Female participants of childbearing potential may be enrolled in the study if the participant: 
1) has a negative pregnancy test at the Eligibility Visit and on the day of the first IP 
injection, 2) has practiced adequate contraception or has abstained from all activities that 
could result in pregnancy for at least 28 days prior to the first IP injection, 3) has agreed to 
continue adequate contraception through 3 months following the last IP injection, and 4) is 
not currently breastfeeding.  
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 (Table 16). Examples are as follows: 
• Barrier method (such as condoms, diaphragm, or cervical cap) used in conjunction with 
spermicide. 
• Intrauterine device. 
• Prescription hormonal contraceptive taken or administered via oral (pill), transdermal 
(patch), subdermal, or IM route. 
• Sterilization of a female participant’s monogamous male partner prior to entry into the 
study. 
Note: periodic abstinence (eg, calendar, ovulation, symptothermal, post-ovulation 
methods) and withdrawal are not acceptable methods of contraception.  

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5.2. 
Exclusion Criteria  
Participants are excluded from the study if any of the following criteria apply: 
1. Is acutely ill or febrile (temperature ≥ 38.0℃/100.4°F) on the day of the first or second 
vaccination. Participants meeting either of these criteria may be rescheduled for 
enrollment/randomization if the event resolves within the vaccination window. 
2. Had prior administration of a ZIKV vaccine candidate during a clinical study investigation. 
3. Had prior administration of a marketed dengue vaccine or dengue vaccine candidate under 
clinical study investigation. 
4. Has a body mass index (BMI) from ≤ 18 or ≥ 35 kg/m2. 
5. History of myocarditis, pericarditis, or myopericarditis. 
6. History of a diagnosis or condition that, in the judgement of the investigator, is clinically 
unstable or may affect participant safety, assessment of safety endpoints, assessment of 
immune response, or adherence to study procedures. “Clinically unstable” is defined as a 
diagnosis or condition requiring significant changes in management or medication within 
the 2 months prior to screening and includes ongoing work-up of an undiagnosed illness 
that could lead to a new diagnosis or condition. 
7. Any medical, psychiatric, or occupational condition, including reported history of drug or 
alcohol abuse, that in the opinion of the investigator, might pose a risk due to 
participation in the study or could interfere with the interpretation of study results. 
8. Has a known or suspected autoimmune disease, including hypothyroidism in relation to 
autoimmune thyroiditis.  
9. Has a history of progressive or severe neurologic disorder or a history of 
neuroinflammatory disease such as Guillain-Barré syndrome. 
10. Has a history of anaphylaxis, urticaria, or other significant AR requiring medical 
intervention after receipt of a vaccine, including an mRNA vaccine or any components of 
an mRNA vaccine. 
11. Has a bleeding disorder that is considered a contraindication to IM injection or phlebotomy. 
12. Has been diagnosed with malignancy within the previous 10 years (excluding 
nonmelanoma skin cancer). 
13. Has received or plans to receive a nonstudy vaccine (including authorized or approved 
vaccines for the prevention of COVID-19) ≤ 28 days prior to the first IP injection or within 

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28 days prior to or after any IP injection. Licensed influenza vaccine received within 
14 days prior to the first IP injection or plans to receive a licensed influenza vaccine 
14 days prior to through 14 days following each IP injection are not exclusionary.  
14. Has a known or suspected impairment or alteration of immune function including the 
following: 
a. Chronic use of oral steroids (equivalent to 20 mg/day prednisone ≥ 12 weeks or 
≥ 2 mg/kg body weight/day prednisone ≥ 2 weeks) within 60 days prior to Day 1 (use 
of inhaled, intranasal, or topical corticosteroids is allowed). 
b. Receipt of parenteral steroids (equivalent to 20 mg/day prednisone ≥ 12 weeks or 
≥ 2 mg/kg body weight/day prednisone ≥ 2 weeks) within 60 days prior to Day 1. 
c. Receipt of immunosuppressive therapy within 3 months prior to Day 1 or planned 
during the 7-month period following study enrollment.  
d. Receipt of immunostimulants within 60 days prior to Day 1. 
e. Receipt of parenteral, epidural, or intra-articular immunoglobulin preparation, blood 
products, and/or plasma derivatives within 3 months prior to Day 1 or planned during 
the 7-month period following study enrollment. 
f. HIV infection or HIV-related disease. 
g. Genetic immunodeficiency. 
15. Has received systemic immunoglobulins or blood products within 3 months prior to the 
day of enrollment. 
16. Has donated ≥ 450 mL of blood products within 28 days of the Day 1 Visit. 
17. Has participated in an interventional clinical study within 28 days prior to the day of 
enrollment or plans to do so while enrolled in this study. 
18. Is an immediate family member or household member of study personnel. 
 
5.3. 
Lifestyle Restrictions 
Not applicable. 
5.4. 
Screen Failures 
Screen failures are defined as participants who consent to participate in the study but are not 
subsequently randomly assigned to study intervention. A minimal set of screen failure information 
is required to ensure transparent reporting of screen failure participants. Minimal information 
includes screen failure details, eligibility criteria, and any SAEs. 

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6. 
INVESTIGATIONAL PRODUCT 
6.1. 
Investigational Products Administered 
mRNA-1893 consists of an mRNA sequence that encodes the full prME structural polyprotein of 
ZIKV in a liposomal formulation. 
The LNP formulation includes 4 lipid excipients: SM-102, a proprietary ionizable amino lipid, and 
the commercially available lipids: cholesterol; 1,2-distearoyl-sn-glycero-3-phosphocholine; and 
1,2-dimyristoyl-sn-glycerol, methoxypolyethyleneglycol (Mui et al 2013). In addition, the 
undiluted (0.20 mg/mL) Drug Product contains 
 
.  
The placebo is 0.9% sodium chloride solution for injection, USP or BP. 
The characteristics of the IPs are presented in Table 8. 
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Table 8: Investigational Products Administered 
 
Treatment Arm A 
Treatment Arm B 
Treatment Arm C 
(2nd 
Administration) 
Treatment Arm C  
(1st administration) and 
Treatment Arm D  
(1st and 2nd 
administrations) 
Investigational 
Product Name: 
mRNA-1893 
mRNA-1893 
mRNA-1893 
Placebo 
Type: 
Vaccine 
Vaccine 
Vaccine 
Normal saline 
Unit Dose 
Strengths: 
0.20 mg/mL 
0.20 mg/mL 
0.20 mg/mL 
0.9% sodium chloride 
solution for injection 
(USP or BP) 
Dosage Levels: 
 µg in 0.5 mL 
(Days 1 and 29) 
 µg in 0.5 mL 
(Days 1 and 29) 
 µg in 0.5 mL 
(Day 29) 
Treatment Arm C: 0.5 mL 
(Day 1) 
Treatment Arm D: 0.5 mL 
(Days 1 and 29) 
Route of 
Administration: 
IM injection 
IM injection 
IM injection 
IM injection 
Source: 
Provided centrally 
by the Sponsor or 
designee 
Provided centrally 
by the Sponsor or 
designee 
Provided centrally 
by the Sponsor or 
designee 
Provided by the Sponsor 
or designee for use as 
both a placebo and a 
diluent to mRNA-1893 
Packaging and 
Labeling: 
mRNA-1893 will 
be provided as a 
0.20 mg/mL 
dispersion in 2R 
glass vials labeled 
as required per 
country 
requirement. 
mRNA-1893 will 
be provided as a 
0.20 mg/mL 
dispersion in 2R 
glass vials labeled 
as required per 
country 
requirement. 
mRNA-1893 will 
be provided as a 
0.20 mg/mL 
dispersion in 2R 
glass vials labeled 
as required per 
country 
requirement. 
The 0.9% sodium 
chloride will bear a 
commercial label and any 
country-specific 
requirements. 
Abbreviations: BP = British Pharmacopeia; IM = intramuscular; USP = United States Pharmacopeia. 
 
6.2. 
Preparation, Handling, Storage, and Accountability of 
Investigational Products 
The Sponsor or designee is responsible for the following: 
• Supplying the IPs. 
• Confirming the appropriate labeling of IP, such that it complies with the legal requirements 
of each country where the study is to be performed. 
The investigator is responsible for acknowledging the receipt of the IPs by a designated staff 
member at the site, including the following: 
• Confirming appropriate temperature conditions have been maintained during transit for all 
IP received and any discrepancies are reported and resolved before use of the IP. 
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• Ensuring that only participants enrolled in the study will receive mRNA-1893 and only 
authorized unblinded site staff will supply or administer the IP. All IPs must be stored in a 
secure, environmentally controlled, and monitored (manual or automated) area in 
accordance with the labeled storage conditions with access limited to the authorized 
unblinded site staff. 
• Ensuring the appropriate dose level of mRNA-1893 is prepared using aseptic techniques 
(vaccine diluted with 0.9% sodium chloride solution for injection [USP or BP] to a 
concentration for delivery of the specified dose level in a volume of 0.5 mL). 
• Maintaining IP records (ie, receipt, accountability, reconciliation, and final disposition 
records) using the Drug Accountability Log. These logs must be available for inspection at 
any time. 
As the appearance of mRNA-1893 and placebo differs, only designated unblinded personnel 
qualified to prepare and/or administer vaccine will be aware of the treatment assignment 
(Section 6.3.2). 
Further description of the IPs and instructions for the receipt, storage, preparation, administration, 
accountability, and destruction of the IPs is provided in the Study mRNA-1893-P201 Pharmacy 
Manual. 
6.2.1. 
Investigational Product Preparation  
mRNA-1893 will be provided as a 0.20 mg/mL dispersion in 2R glass vials labeled as required per 
country requirement. The vaccine will be diluted to a concentration for delivery of the specified 
dose level in a volume of 0.5 mL. 
6.2.2. 
Investigational Product Administration 
The IP will be administered as an IM injection into the deltoid muscle, and each dose will have a 
volume of 0.5 mL. Preferably, the first dose should be injected into the nondominant arm and the 
second dose should be injected into the same arm as the first dose.  
The IP will be prepared for injection as a single 0.5-mL dose for each participant based on the 
treatment arm and randomization assignment, as detailed in the Study mRNA-1893-P201 
Pharmacy Manual. Unblinded pharmacy personnel, who will not participate in any other aspect of 
the study, will perform IP accountability, dose preparation, and administration. The investigator 
will designate an unblinded clinical team member to provide oversight to the vaccination so that 
it proceeds according to the procedures stipulated in this study protocol and the Study 
mRNA-1893-P201 Pharmacy Manual. Study-specific training will be provided.  

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At each visit when IP is administered, participants will be monitored for a minimum of 30 minutes 
after IP injection. Assessments will include vital sign measurements and monitoring for immediate 
local or systemic reactions (Table 1).  
Eligibility for subsequent IP injection is determined by following the criteria outlined in 
Section 7.1.  
The study site will be appropriately staffed, and staff will be trained and experienced in delivering 
emergency resuscitation and will have stocked rescue medications (such as epinephrine, steroids, 
antihistamines, and intravenous fluids) should any severe AR (eg, anaphylaxis or urticaria) occur 
that requires immediate intervention.  
Further instructions for the preparation and administration of mRNA-1893 are described in the 
Study mRNA-1893-P201 Pharmacy Manual. 
6.2.3. 
Investigational Product Packaging and Labeling 
All IPs used in this study will be prepared, packaged, and labeled in accordance with the standard 
operating procedures of the Sponsor or those of its designee, US Title 21 Code of Federal 
Regulations (CFR), Good Manufacturing Practice guidelines, ICH GCP guidelines, guidelines for 
Quality System Regulations, and applicable regulations. 
A 0.9% sodium chloride solution for injection (USP or BP) (normal saline) for use as placebo and 
mRNA-1893 preparation will contain a commercial label and country requirements as necessary. 
6.2.4. 
Investigational Product Storage 
mRNA-1893 must be stored at -25ºC to -15°C (-13ºF to 5ºF). mRNA-1893 must be received by 
designated unblinded personnel at the study site, handled and stored safely and properly, kept in a 
secured location with restricted access (unblinded pharmacy staff only), and protected from 
moisture and light until it is prepared for administration.  
The 0.9% sodium chloride solution for injection (USP or BP) must be stored at 20ºC to 25ºC (68ºF 
to 77ºF) in a restricted access area (unblinded pharmacy staff only). 
6.2.5. 
Investigational Product Accountability 
The unblinded designee must maintain an accurate record of the shipment receipt, the inventory at 
the site, dispensing of study treatment, and the return to the Sponsor or alternative disposition of 
used/unused products in a drug accountability log. Drug accountability will be noted by the 
unblinded clinical research associate (CRA) during site visits and at the completion of the study. 
For further direction, refer to the Study mRNA-1893-P201 Pharmacy Manual. 

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6.2.6. 
Investigational Product Handling and Disposal 
The designated unblinded CRA will reconcile the IP at the interim monitoring visit and at the end 
of the study for compliance. Once fully reconciled at the site, the IP can be destroyed at the 
investigational site or by a Sponsor-selected third party, as appropriate. 
The IP may be destroyed at the study site only if permitted by local regulations and authorized by 
the Sponsor. A Certificate of Destruction must be obtained and sent to the Sponsor or designee. 
For further direction refer to mRNA-1893-201 Pharmacy Manual. 
6.3. 
Randomization and Blinding 
6.3.1. 
Randomization 
The randomization will be in a blinded manner using a centralized Interactive Response 
Technology (IRT), in accordance with pre-generated randomization schedules. Approximately 
800 participants will be randomized in parallel according to a 1:1:1:1 randomization ratio to the 
4 treatment arms. Randomization was stratified by participants’ baseline flavivirus serostatus 
under the original protocol. Under this protocol amendment, randomization will be stratified only 
by participants’ region (continental US and Puerto Rico). Only the unblinded pharmacy personnel 
(Section 6.3.2) will have controlled access to which arm the participant is randomly assigned. 
6.3.2. 
Blinding 
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 electronic data 
capture (EDC) is locked and CSR has been written, with the following exceptions:  
• Unblinded pharmacy personnel (of limited number) will be assigned to IP accountability 
procedures and will prepare and administer mRNA-1893 or placebo to all participants. 
These pharmacy 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 (Section 6.3.3). 
• Unblinded site monitors, not involved in other aspects of monitoring, will be assigned as 
the IP accountability monitors. They will have responsibilities to ensure that sites are 
following all proper IP accountability, preparation, and administration procedures. 
• An unblinded statistical and programming team will perform the preplanned Day 57 
interim analysis (IA) (Section 9.5). A limited number of Sponsor team members will be 

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pre-specified to be unblinded to the IA results and will not communicate the results of 
interim analyses to the blinded investigators, study site staff, clinical monitors, or 
participants.  
The IP 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. Only delegated unblinded 
site staff will conduct the vaccination procedure. Once each vaccination 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.  
Study site blinded staff will remain blinded to individual treatment assignments until the end of 
the study. 
6.3.3. 
Unblinding 
Except in the case of medical necessity, a participant’s treatment assignment should not be 
unblinded without the approval of the Sponsor. If a participant becomes seriously ill or pregnant 
during the study, the blind will be broken only if knowledge of the treatment assignment will affect 
that participant’s clinical management. In the event of a medical emergency requiring 
identification of individual treatment assignment, the investigator will make every attempt to 
contact the Sponsor medical lead or designee to explain the need for unblinding within 24 hours 
of opening the code. The investigator will be responsible for documenting the time, date, reason 
for unblinding, and the names of the personnel involved. The investigator (or designee) will have 
access to unblind participants within IRT. All unblindings will be tracked via an audit trail in IRT 
and documented in the final study report. 
If unblinding should occur (by either accidental unblinding or emergency unblinding) before 
completion of the study, the investigator must promptly contact the Sponsor and document the 
circumstances on the appropriate forms. 
The Sponsor will remain blinded to IP assignment throughout the treatment phase for each 
individual treatment arm of the study up until each specified time point for interim analyses, as 
outlined in Section 9.5. 
6.4. 
Investigational Product Compliance 
All doses of IP will be administered at the study site under direct observation of unblinded 
pharmacy personnel and appropriately recorded (date and time) in the electronic case report forms 
(eCRFs). Unblinded pharmacy personnel will confirm that the participant has received the entire 
dose of IP. If a participant does not receive IP or does not receive all of the planned doses, the 
reason for the missed dose will be recorded.  

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Participants who miss the second vaccination due to noncompliance with the visit schedule will 
still be required to follow the original visit and testing schedule as described in the protocol. Unless 
consent is withdrawn, a participant who withdraws or is withheld from receiving the second dose 
of IP will remain in the study and complete all safety and immunogenicity assessments required 
through the scheduled EOS.  
The study site is responsible for ensuring participants comply with the study windows allowed. If 
a participant misses a visit, every effort should be made to contact the participant and complete a 
visit within the defined time window (Table 1 and Table 2). 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 (eg, eDiary review for reactogenicity, immune 
testing, as applicable).  
6.5. 
Prior and Concomitant Medications and Therapies 
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. 
6.5.2. 
Concomitant Medications and Therapies 
At each study visit the following concomitant medications and vaccines must be recorded in the 
eCRF: 
• All concomitant medications administered from the Eligibility Visit through 28 days after 
the last IP injection. 
• Any nonstudy vaccines administered during the period starting 28 days before the first IP 
injection and ending at the last study visit. 
• Any concomitant medications and vaccines listed in Section 6.5.3. 
• Any concomitant medications and vaccines relevant to an SAE/AESI or administered from 
the signing of the informed consent form (ICF) through the last study visit for the treatment 
of an SAE/AESI. 
• Any antipyretic or analgesic to treat or prevent fever or pain within 7 days after IP injection, 
including day of injection.  

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• Participants will be asked to record in the eDiary any antipyretic or analgesic taken to treat 
or prevent fever or pain within 7 days (including the day of injection) after IP injection. 
Reported antipyretic or analgesic medications should be recorded in the source document 
by the site staff during the post-IP injection study visits or via other participant interactions 
(eg, telephone calls). 
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 nonstudy vaccines will not require 
withdrawal of the participant from the study but may determine a participant’s evaluability in the 
Per-Protocol (PP) analyses. Analysis sets are described in Section 9.3. 
• 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 Vaccination Period or 60 days after the first IP injection. 
For corticosteroids, this will mean that prednisone ≥ 20 mg/day or the equivalent is not 
permitted. Inhaled and topical steroids are allowed. 
• Long-acting immune-modifying drugs administered at any time during the Vaccination 
Period or 60 days after the first IP injection (eg, infliximab). 
• A nonstudy vaccine not foreseen by the study protocol administered during the Vaccination 
Period through 28 days after each IP injection. 
• Immunoglobulins and/or any blood products administered up to Day 57. 
6.6. 
Intervention After the End of the Study 
Any SAE/AESI and unexpected AEs occurring after the end of the study and considered to be 
caused by the IP must be reported to the Sponsor. 

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7. 
DELAY OR DISCONTINUATION OF INVESTIGATIONAL 
PRODUCT AND PARTICIPANT WITHDRAWAL FROM THE 
STUDY 
7.1. 
Criteria for Delay of Investigational Product Administration and 
Contraindication to Subsequent Administrations 
Prior to receiving a second vaccination, participants will be reassessed to ensure that they continue 
to meet eligibility requirements as outlined below.  
The following events in a participant constitute absolute contraindications to any further 
administration of the IP to that participant. If any of these events occur during the study, the 
participant must not receive additional doses of IP but will be encouraged to continue study 
participation for safety through approximately 6 months following the vaccination (Section 7.2):  
• Anaphylaxis or systemic hypersensitivity reaction following the administration of IP.  
• Any SAE or AESI judged by investigator or Sponsor to be related to IP. 
• Pregnancy. 
• Any clinically significant change in vital sign measurements or general condition that, in 
the opinion of the investigator, poses an additional risk to the participant if he/she continues 
to participate in the study. 
The following events constitute contraindications to administration of IP at certain points in time, 
and if any of these events occur at the time scheduled for injection, the participant may be injected 
at a later date, within the time window specified in Table 1, or the participant may be withdrawn 
from dosing at the discretion of the investigator (Section 7.3):  
• Acute moderate or severe infection with or without fever at the time of injection. 
• Fever defined as body temperature ≥ 38.0°C (100.4°F) at the time of injection. 
Participants with a minor illness without fever, as assessed by the investigator, can be administered 
IP. Participants with a fever of 38.0°C (100.4°F), or higher will be contacted within the time 
window acceptable for participation and re-evaluated for eligibility. 
7.2. 
Discontinuation of Investigational Product 
A “withdrawal” from the IP refers to any participant who does not receive the vaccination 
series. The investigator should make all efforts to ensure that the participants remain in the study 
to ensure a proper safety follow-up and medical care if needed, and document reason for 
participant withdrawal from study injection. 

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Information relative to premature discontinuation of the IP will be documented in the eCRF. The 
investigator will document which of the following reasons was responsible for withdrawal: 
• SAE. 
• AESI. 
• AE (non-SAE). 
• Dosing error. 
• Other (specify). 
Participants who withdraw from further study injection for any reason after their first dose but do 
not withdraw consent will complete all study procedures through EOS, as outlined in Table 1. 
7.3. 
Participant Withdrawal from the Study 
Participants can withdraw consent and discontinue from the study at any time, for any reason, 
without prejudice to further treatment the participant may need to receive.  
Participants who are withdrawn will not be replaced. 
From an analysis perspective, a “withdrawal” from the study refers to a situation wherein a 
participant does not return for the final visit foreseen in the protocol. 
All data collected until the date of withdrawal or last contact of the participant will be used for the 
analysis, including collected specimens. 
A participant is considered a “withdrawal” from the study when no study procedure has occurred, 
no follow-up has been performed, and no further information has been collected for that participant 
from the date of withdrawal or last contact. 
Investigators will attempt (eg, 3 documented telephone calls) to contact those participants who do 
not return for scheduled visits or follow-up. 
Information relative 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). 
• Death. 
• Lost to follow-up (LTFU). 

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• Physician decision (specify). 
• Pregnancy. 
• Protocol violation. 
• Study terminated by Sponsor. 
• Withdrawal of consent by participant (specify). 
• Other (specify). 
Participants who are withdrawn from the study because of SAEs/AESIs/AEs must be clearly 
distinguished from participants who are withdrawn for other reasons. Investigators will follow-up 
with participants who are withdrawn from the study as a result of an SAE, AESI or AE until 
resolution of the event. 
Participants who withdraw 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 participants withdraw consent for disclosure of future information, the Sponsor may retain and 
continue to use any data collected before such a withdrawal of consent. 
The Sponsor will continue to retain and use all research results that have already been collected 
for the study evaluation. 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/she repeatedly fails to return for scheduled visits 
without stating an intention to withdraw consent and is unable to be contacted by the study site. 
The following actions must be taken if a participant fails to return to the clinic for a required study 
visit: 
• The site must attempt to contact the participant and reschedule the missed visit as soon as 
possible, counsel the participant on the importance of maintaining the assigned visit 
schedule, and ascertain whether the participant wishes to and/or should continue in the 
study. 
• Before a participant is deemed LTFU, the investigator or designee must make every effort 
to regain contact with the participant (where possible, 3 documented 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. 

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• Should the participant continue to be unreachable, they will be considered to have 
withdrawn from the study.  
• A participant should not be considered LTFU until due diligence has been completed. The 
date of withdrawal/LTFU should be the date of last contact with the participant where 
safety status of the participant was assessed (eg, clinic visit, telephone call). 
7.5. 
Circumstances to Delay or Discontinue the Study Independent of 
Investigational Product and Participant 
There are instances such as public health emergencies or natural disasters that may directly affect 
the initial plan for the study conduct. Those circumstances may correspond but are not limited to 
new emerging infectious diseases such as the current COVID-19 pandemic. Cognizant of the 
challenges that may arise from those situations, an operational plan will be elaborated in a separate 
document describing potential repercussions, approaches to protect study participants, and factors 
to consider for decision to suspend or continue the ongoing study. This document follows FDA 
Guidance on Conduct of Clinical Trials of Medical Products During COVID-19 Public Health 
Emergency updated on 03 Jun 2020 (DHHS 2020). Refer also to Section 8. 

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8. 
STUDY ASSESSMENTS AND PROCEDURES  
Study procedures and time points are summarized in the SOAs (Table 1 and Table 2). Protocol 
waivers or exemptions are not allowed. Adherence to the study design requirements, including 
those specified in Table 1 and Table 2, is essential and required for study conduct.  
Before performing any study procedures, all potential participants will sign an ICF 
(Section 11.1.6). Potential participants will be evaluated (interview and physical examination) to 
determine their eligibility to participate in the study according to the inclusion and exclusion 
criteria (Section 5.1 and Section 5.2, respectively). All eligibility evaluations must be completed 
and reviewed to confirm that potential participants meet all eligibility criteria. If a participant is 
not enrolled in the study, the reason for eligibility failure must be recorded. The investigator will 
maintain a log to record details of all participants evaluated and to confirm eligibility or record 
reasons for failure, as applicable.  
A participant can also be seen for an unscheduled visit at any time during the study. An 
unscheduled visit may be prompted by reactogenicity issues, new or ongoing AEs, or a suspicion 
of a flavivirus infection. 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 to 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 updated on 03 Jun 2020 (DHHS 2020), investigators may 
convert study site visits to telemedicine visits with the approval of the Sponsor. If a participant 
cannot attend a study site visit (scheduled or unscheduled) with the exception of Day 0, Day 1, and 
Day 29 Visits, a home visit is acceptable if performed by appropriately delegated study site staff 
or a home healthcare service provided by the Sponsor. If neither a participant visit to the study site 
nor a home visit to the participant is possible (with the exception of Day 0, Day 1, and Day 29 
Visits), a safety telephone call should be performed that includes the assessments scheduled for 
the safety telephone calls scheduled on Days 112 through 168 (Table 1). Such action should be 
taken to protect the safety and well-being of study participants and clinical site staff or to comply 
with state or municipal mandates. 
8.1. 
Demographics and Other Baseline Characteristics 
Demographic information (eg, sex, age, race, and ethnicity) and other baseline characteristics (eg, 
weight and height) will be recorded on the appropriate eCRF page during the eligibility evaluation.  

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The medical history of each participant will be obtained by interviewing the participant or by 
reviewing the participant’s medical records. Any pre-existing conditions or signs and/or symptoms 
present prior to the signature of the ICF must be included on the Medical History page of the eCRF. 
8.2. 
Clinical Laboratory Assessments  
8.2.1. 
Baseline and Safety Laboratory Assessments 
There are no screening criteria based on the flavivirus serostatus, meaning all participants are 
enrolled regardless of serostatus. However, this baseline flavivirus status will be confirmed by 
serology testings (dengue IgG and IgM, West Nile IgG and IgM) performed on a blood sample 
collected prior to administration of the first vaccination in order to eventually ensure that an 
approximate equal distribution of participants among subgroups is respected for the statistical 
analysis. 
A point-of-care urine pregnancy test will be performed at the Eligibility Visit and before each IP 
injection (or at any time at the discretion of the investigator) for all female participants of 
childbearing potential. 
The FSH level may be measured at the discretion of the investigator to confirm menopausal status. 
There are no screening safety laboratory tests at the time of the eligibility evaluation of the 
participant. However, additional tests may be performed for safety reasons at any time during the 
study if determined necessary by the investigator or required by local regulations. Specifically, if 
the participant presents with signs or symptoms evoking a flavivirus infection, standard-of-care 
tests and treatment will apply, and results will be reported in the source documents and in the AE 
section of the eCRF. 
8.3. 
Immunogenicity and Efficacy Assessments 
8.3.1. 
Immunogenicity Assessments 
Blood samples for analysis of the immunogenicity will be collected as described in Table 1 and 
Table 2. On Days 1 and 29, blood samples for immunogenicity assessment will be collected 
before vaccination.  
The approximate blood volumes to be collected from each participant during the study are 
presented in Section 8.4.  
The following antibody-mediated immunogenicity assessments will be performed:  
• Serum ZIKV-specific nAb titers, as measured by PRNT assay, MN assay, and RVP assay. 
• Serum ZIKV-specific bAb concentrations, as measured by ligand binding assay. 

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The following CMI assessments will be performed with the additional blood samples collected for 
PBMC isolation from the CMI subset participants (Table 1 and Table 2): 
• Frequency of ZIKV-specific T cells, as measured by ICS assay and sequencing. 
• Frequency of ZIKV-specific B cells, as measured by ELISpot.  
• Other techniques that may be relevant to assesses the profile characteristics of the 
ZIKV-specific T- and B-cell responses may be also included. 
Sample aliquots will be designed to ensure that backup samples are available and that adequate 
vial volumes may allow further 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 Laboratory Manual. 
Testing will be performed in laboratories designated by the Sponsor. 
8.3.2. 
Efficacy Assessments 
Blood samples for detection of asymptomatic flavivirus infection will be collected as described in 
Table 1 and Table 2. Asymptomatic flavivirus infections will be assessed through quantification 
of nonstructural protein 1-specific bAbs, as measured by enzyme-linked immunosorbent assay 
(ELISA).  
In case of signs or symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas 
where the study will be performed), an additional blood sample will be collected to confirm the 
diagnosis via specific serology (IgM antibody capture ELISA and virus neutralization assay) and 
RT-PCR. 
8.4. 
Total Blood Volume 
All samples (blood, serum, or PBMCs) must be collected in accordance with acceptable laboratory 
procedures and will be processed, labeled, and stored in accordance with the instructions in the 
Laboratory Manual. 
The approximate blood volumes to be collected from each participant during the Vaccination 
Period and Extension Period are provided in Table 9 and Table 10, respectively. 

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Table 9: Total Planned Approximate Blood Volumes for the Vaccination Period  
Assessment 
Approximate 
Blood Volume 
per Sample 
Scheduled Number 
of Collections1 
Total 
Approximate 
Amount of 
Scheduled 
Blood Volume 
Flavivirus status baseline level by 
ELISA2 
8 mL 
1 
8 mL 
Serum neutralizing antibodies against 
ZIKV by neutralization assays 
12 mL 
7 
84 mL 
Serum binding antibodies against 
ZIKV by ELISA 
Antibodies against envelope- and 
NS1-based antigens by ELISA (for 
asymptomatic ZIKV case detection) 
Quantification and qualification of 
ZIKV-specific T cells and ZIKV-
specific B cells (CMI subset of 
participants)3 
88 mL (for PBMC 
collection) 
5 
440 mL 
Participant Approximate Maximum Total4 
532 mL 
Exploratory research6 
60 mL  
1 
60 mL 
Only in Case of Signs or Symptoms Suggesting a Flavivirus Infection5 
Dengue by serology and RT-PCR 
2 mL 
– 
2 mL 
Zika by serology and RT-PCR 
6 mL 
– 
6 mL 
Abbreviations: CMI = cell-mediated immunity; ELISA = enzyme-linked immunosorbent assay; IgG = immunoglobulin G; IgM = 
immunoglobulin M; NS1 = nonstructural protein 1; PBMC = peripheral blood mononuclear cell; RT-PCR = reverse transcription 
polymerase chain reaction; ZIKV = Zika virus. 
1 
Additional blood collections may be required at the discretion of the investigator to follow-up on abnormal results. 
2 
Flavivirus testing by ELISA at baseline will include testing for dengue and West Nile IgG and IgM measurements. 
3 
Peripheral blood mononuclear cells will be isolated from blood samples collected from the CMI subset participants, which is 
a subset of participants selected from approximately 4 sites that have experience in human cell collection. 
4 
The approximate blood volume of 532 mL includes the volume collected for the PBMC collection and other assays in the 
CMI subset participants over a period of 6 months. 
5 
In case of signs or symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas where the study will be 
performed), an additional blood sample will be collected to confirm the diagnosis via specific serology and RT-PCR. 
6 
On Day 57, an additional blood sample (60 mL) will be collected from participants enrolled at 1 US site for exploratory 
research, in particular for animal challenge studies (Section 11.1.10). 
 

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Table 10: Total Planned Approximate Blood Volumes for the Extension Period 
Assessment 
Approximate 
Blood Volume per 
Sample 
Scheduled Number 
of Collections1 
Total 
Approximate 
Amount of 
Scheduled 
Blood Volume 
Serum neutralizing antibodies against 
ZIKV by neutralization assays 
12 mL 
3 
36 mL 
Serum binding antibodies against 
ZIKV by ELISA 
Antibodies against envelope- and 
NS1-based antigens by ELISA (for 
asymptomatic ZIKV case detection) 
Quantification and qualification of 
ZIKV-specific T cells and ZIKV-
specific B cells (CMI subset of 
participants)2 
88 mL 
3 
264 mL 
Participant Approximate Maximum Total3 
300 mL 
Only in Case of Signs or Symptoms Suggesting a Flavivirus Infection4 
Dengue by serology and RT-PCR 
2 mL 
– 
2 mL 
Zika by serology and RT-PCR 
6 mL 
– 
6 mL 
Abbreviations: CMI = cell-mediated immunity; ELISA = enzyme-linked immunosorbent assay; NS1 = nonstructural protein 1; 
PBMC = peripheral blood mononuclear cell; RT-PCR = reverse transcription polymerase chain reaction; ZIKV = Zika virus. 
1 
Additional blood collections may be required at the discretion of the investigator to follow-up on abnormal results. 
2 
Peripheral blood mononuclear cells will be isolated from blood samples collected from the CMI subset participants, which is 
a subset of participants selected from approximately 4 sites that have experience in human cell collection. 
3 
The approximate blood volume of 300 mL includes the volume collected for the PBMC collection and the other assays in 
the CMI subset participants over a period of 18 months with a 6-month periodicity; for the other participants, the blood 
volume collected is approximately 36 mL. 
4 
In case of signs or symptoms suggesting a flavivirus infection (mostly dengue and Zika in the areas where the study will be 
performed), an additional blood sample will be collected to confirm the diagnosis via specific serology and RT-PCR. 
 
8.5. 
Safety Assessments 
The planned time points for all safety assessments are provided in Table 1 and Table 2. 
Safety assessments will include monitoring and recording of the following for each participant: 
• Solicited local and systemic ARs (Section 11.2.3; Appendix 2) that occur during the 7 days 
following each IP injection (ie, the day of injection and 6 subsequent days). Solicited ARs 
will be recorded daily using eDiaries (Section 8.5.1). 

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• Unsolicited AEs observed or reported during the 28 days following each IP injection (ie, 
the day of injection and 27 subsequent days). Unsolicited AEs are AEs that are not included 
in the protocol-defined solicited ARs (Section 11.2.3; Appendix 2). Unsolicited AEs will 
be captured during safety telephone calls or at site visits and recorded on the participant’s 
AE CRF. 
• AEs leading to discontinuation from IP and/or study participation throughout the entire 
study duration (up to Day 700).  
• MAAEs (Section 11.2.4; Appendix 2) from Day 1 throughout the entire study duration (up 
to Day 700). 
• SAEs and AESIs (Section 11.2.2; Appendix 2) from Day 1 throughout the entire study 
duration (up to Day 700). 
• Physical examination findings (Section 8.5.3). 
• Vital sign measurements (Section 8.5.4). 
8.5.1. 
Electronic Diary Assessments 
At the time of consent, participants must confirm they are willing to complete an eDiary using 
either an application downloaded to their smartphone or using a device that is provided at the time 
of enrollment. This study will utilize the Medidata Patient Cloud Application as the eDiary. This 
application allows for real-time data collection on a fully audited and 21 CFR Part 11-compliant 
system directly from participants, ensuring that data are attributable, legible, contemporaneous, 
original, and accurate at all critical collection points. As the key diary data capture is unsupervised 
in participants’ own homes, through the use of programmed data entry windows and time stamps, 
the Patient Cloud application ensures the data are collected as per the trial design. By leveraging 
electronic data collection, Medidata’s Patient Cloud Application enables participants an easier way 
to collect data - seamlessly integrated into their daily routines - while similarly allowing site staff, 
contract research organizations (CROs), and sponsors immediate access to critical data actions. 
Before enrollment on Day 1, the participant will be instructed to download the eDiary application 
or will be provided an eDiary device to record solicited ARs (Section 11.2.3; Appendix 2) on 
Day 1. 
At each vaccination visit, participants will be instructed (Day 1) or reminded (Day 29) on 
thermometer usage to measure body temperature and ruler usage to measure injection site 
erythema and swelling/induration (hardness). Oral temperature is the preferred route of 
measurement. 

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At each vaccination visit, participants will record data into the eDiary starting at least 30 minutes 
after IP injection under supervision of the study site staff to ensure successful entry of assessments. 
The site staff will perform any retraining as necessary. Study participants will continue to record 
data in the eDiary after they leave the clinic, preferably in the evening and at the same time each 
day, on the day of injection, and for 6 days following each injection. 
Participants will record the following data in the eDiary:  
• Solicited local and systemic ARs (Section 11.2.3; Appendix 2) that occur on the day of 
each dose and during the 7 days after injection (ie, the day of injection and 6 subsequent 
days). Any solicited AR that is ongoing beyond Day 7 will be recorded until it is no longer 
reported, not to exceed 28 days after each injection. Solicited ARs recorded in eDiaries 
beyond Day 7 should be reviewed by study site staff either during the next scheduled 
telephone call or at the next study site visit (Table 1 and Table 2).  
• 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. 
• Measurements, as applicable, for solicited local ARs (injection site erythema and 
swelling/induration); the size measurements will be performed using the ruler provided by 
the study site. 
• All medications taken on the day of each dose and during the 28 days after injection (ie, 
the day of injection and 27 subsequent days). Participants will be queried by the eDiary 
whether any medications were taken to treat or prevent pain or fever on a day of injection 
or for the 6 subsequent days.  
The eDiaries will be the main source documents allowed for solicited local or systemic ARs 
(including body temperature measurements). Participants will be instructed to complete eDiary 
entries daily. If assessments are not recorded for a given day, the participant will have a limited 
time window on the following day to complete qualitative assessments for the previous day, 
excluding measurements of body temperature and of any injection site erythema or 
swelling/induration. Any new safety information reported during safety telephone calls or at site 
visits (including a solicited AR) not already captured in the eDiary will be described in the source 
documents as a verbally reported event. Any solicited AR reported in this manner must be entered 
on the Reactogenicity page of the eCRF. 

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Procedures for transferring eDiary data to the eCRF are presented in the Study mRNA-1893-P201 
Study Manual. Study site staff will review eDiary data with participants at the Day 8 and Day 36 
Visits. 
8.5.2. 
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. The 
participant will be interviewed according to the script, and information will be collected about the 
occurrence of any MAAEs, SAEs, AESIs, or AEs leading to study withdrawal, concomitant 
medications associated with those events, and any nonstudy vaccinations.  
The timing of the safety telephone calls is provided in Table 1.  
All safety information described by the participant must be documented in source documents and 
not documented on the script used for the safety telephone contact. 
8.5.3. 
Physical Examination 
A full physical examination will include, at a minimum, assessments of the cardiovascular, 
respiratory, gastrointestinal, and neurological systems according to standard medical practice. 
Weight and height will be recorded and BMI will be calculated (body weight [kg] ÷ height [m]2) 
during the eligibility evaluation. 
A symptom-directed physical examination will be performed at the discretion of the investigator 
each time the participant is in the clinic when a full physical examination is not otherwise specified. 
Symptom-directed physical examinations will include, at a minimum, inspection of the general 
status of the participant, according to standard medical practice. Additional elements of the 
physical examination should be added on the basis of symptoms described during the interview of 
the participant. Prior to IP injection and at follow-up visits, female participants should also be 
queried for new onset of menarche.  
Investigators should pay special attention to clinical signs related to previous serious illnesses. 
Treatment of any abnormality observed during physical examination should be performed 
according to local medical practice outside the study or by referral to an appropriate healthcare 
provider at the discretion of the investigator. Any clinically significant finding identified during a 
study visit should be reported as an MAAE. 
Significant new findings that begin or worsen after informed consent must be recorded on the AE 
page of the eCRF. 

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8.5.4. 
Vital Sign Measurements 
Vital sign measurements will include body temperature (preferred route is oral), systolic and 
diastolic blood pressure, heart rate, and respiratory rate. The participant will be seated for at least 
5 minutes before all measurements are taken. Vital signs will be collected prior to study procedures 
and at least 30 minutes after IP injection, prior to discharge of the participant from the study site.  
Febrile participants at Day 1 and Day 29 Visits (fever is defined as a body temperature 
≥ 38.0°C/100.4°F) may be rescheduled within the relevant window periods. 
When procedures overlap and are scheduled to occur at the same time point, the order of 
procedures should be vital sign measurements and then the blood collection. 
If any of the vital sign measurements meet the toxicity grading criteria for clinical abnormalities 
(Table 13) of Grade 3 or greater, the abnormal value and grade will be documented on the AE page 
of the eCRF (unless there is another known cause of the abnormality that would result in an AE 
classification). The investigator will continue to monitor the participant with additional 
assessments until the vital sign value has reached the reference range, returns to the vital sign value 
at baseline, is considered stable, or until the investigator determines that follow-up is no longer 
medically necessary. 
8.6. 
Adverse Events and Serious Adverse Events 
The definitions and procedures for the recording, evaluation, follow-up, and reporting of AEs 
(solicited ARs, unsolicited AEs, and MAAEs) and SAEs are presented in Appendix 2. 
Adverse events will be reported by the participant. The investigator and any qualified designees 
are responsible for detecting, documenting, and recording events that meet the definition of an AE 
or SAE and remain responsible for following up on AEs that are serious, considered related to the 
administration of IP or study procedures, or that caused the participant to discontinue the study. 
8.6.1. 
Time Period and Frequency for Collecting AE and SAE Information 
Medical occurrences that begin before the first vaccination with mRNA-1893 but after obtaining 
informed consent will be recorded in the Medical History/Current Medical Conditions section of 
the eCRF, 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. 
The time periods for collection, recording, and reporting of solicited ARs, unsolicited AEs, and 
SAEs are found in Appendix 2. 
Adverse events may be collected as follows: 
• Observing the participant. 

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• Receiving an unsolicited complaint from the participant. 
• Questioning the participant in an unbiased and nonleading manner. 
Solicited ARs will be collected from the day of injection through 6 days after each IP injection 
(Days 1 through 7 and Days 29 through 35). Other (unsolicited) AEs will be collected from the 
day of injection through 28 days after each IP injection (Days 1 through 29 and Days 29 through 
57). 
Serious AEs will be collected from the first IP injection until the last follow-up visit after the last 
IP injection at the time points specified in the SOAs (Table 1 and Table 2).  
All SAEs will be recorded and reported to the Sponsor or designee immediately, and under no 
circumstance should this exceed 24 hours, as indicated in Section 11.2.11. The investigator will 
submit any updated SAE data to the Sponsor within 24 hours of it being available. 
An abnormal value or result from a clinical or laboratory evaluation (eg, a radiograph, an 
ultrasound, or an electrocardiogram) can also indicate an AE if it is determined by the investigator 
to be clinically significant (eg, leads to dose modification or study drug discontinuation or meets 
any serious criteria). If this is the case, it must be recorded in the source document and as an AE 
on the appropriate AE page of the eCRF. 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 conclusion of the study 
participation. However, if the investigator learns of any SAE, including a death, at any time after 
a participant has been discharged from the study, and he/she considers the event to be reasonably 
related to the IP or study participation, the investigator must promptly notify the Sponsor. 
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 and Canada): 
 
• SAE Fax line (USA and Canada): 
 
8.6.2. 
Method of Detecting AEs and SAEs 
The method of recording, evaluating, and assessing causality of AE and SAE and the procedures 
for completing and transmitting SAE reports are provided in Appendix 2. 
PPD
PPD
PPD

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Electronic diaries have specifically been designed for this study by the Sponsor. The diaries will 
include pre-listed AEs (solicited ARs) and intensity scales. In addition to the eDiaries, delegated 
site staff will interview the participant to assess the occurrence of any unsolicited AEs, SAEs, and 
medications taken. The investigator or designated site staff will transcribe the collected 
information into the eCRF. 
The investigator is responsible for the documentation of AEs regardless of treatment 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 requiring immediate notification to the Sponsor or its 
designated representative. 
Care will be taken not to introduce bias when detecting AEs and/or SAEs. Open-ended and 
nonleading verbal questioning of the participant is the preferred method to inquire about 
AE occurrences. 
8.6.3. 
Follow-Up of AEs and SAEs 
After the initial AE/SAE report, the investigator is required to proactively follow each participant 
at subsequent visits/contacts.  
All AEs and SAEs (as defined in Appendix 2) 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). Further information on follow-up procedures is given in Appendix 2. 
8.6.4. 
Adverse Events of Special Interest 
The definition of AESIs and reporting of AESIs is presented in Section 11.2.5 and Section 11.2.12 
(Appendix 2), respectively. Adverse events of special interest for this protocol, including 
myocarditis/pericarditis and anaphylaxis, among others, are listed in Section 11.2.13 
(Appendix 2). For Centers for Disease Control and Prevention (CDC) working case definitions of 
myocarditis, pericarditis, and myopericarditis occurring after receipt of COVID-19 mRNA 
vaccines, refer to Section 11.4 (Appendix 4).  
8.6.5. 
Regulatory Reporting Requirements for SAEs 
• Prompt notification by the investigator to the Sponsor of an SAE is essential so that legal 
obligations and ethical responsibilities towards the safety of participants and the safety of 
an IP 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 an IP under clinical investigation. The 

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Sponsor will comply with country-specific regulatory requirements relating to safety 
reporting to the regulatory authority, Institutional Review Boards (IRBs)/Independent 
Ethics Committees (IECs), and investigators. 
• Investigator safety reports must be prepared for suspected unexpected serious adverse 
reactions 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/AESI or 
other specific safety information (eg, summary or listing of SAEs/AESIs) from the Sponsor 
will review and then file it along with the IB and will notify the IRB/IEC, if appropriate, 
according to local requirements. 
8.6.6. 
Pregnancy 
Details of all pregnancies occurring in female participants after the administration of IP must be 
reported to the Sponsor or designee within 72 hours of learning of the pregnancy following the 
procedures outlined in Appendix 2. Abnormal pregnancy outcomes (eg, spontaneous abortion, 
fetal death, stillbirth, congenital anomalies, ectopic pregnancy) are considered SAEs. 
Further information on the collection of pregnancy information is given in Appendix 2. 
8.7. 
Treatment of Overdose 
In the event of an overdose, the investigator should do the following: 
1. Contact the Medical Monitor SAE hotline immediately. 
2. Closely monitor the participant for any AE/SAE and laboratory abnormalities until the last 
safety follow-up visit.  
3. Report any signs or symptoms associated with the overdose as an AE and record details in 
the relevant AE/SAE sections in the eCRF. 
4. Document the quantity of the excess dose in the eCRF. 
8.8. 
Pharmacokinetics 
Pharmacokinetic parameters are not evaluated in this study.  
8.9. 
Pharmacodynamics  
Pharmacodynamic parameters are not evaluated in this study.  

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8.10. 
Biomarkers 
Analysis of biomarkers for biological activity will include the evaluation of the ZIKV-specific 
antibody response, such as nAbs and bAbs, and additionally relevant immunological variables 
(Section 8.3), which may correlate with vaccine efficacy.  
8.11. 
Medical Resource Utilization and Health Economics 
Medical Resource Utilization and Health Economics parameters are not evaluated in this study. 

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9. 
STATISTICAL CONSIDERATIONS 
9.1. 
Statistical Hypotheses 
The study objectives are presented in Section 3. 
There is no hypothesis testing in this study.  
9.2. 
Sample Size Determination 
The sample size for this study is not driven by statistical assumptions for formal hypothesis testing. 
This sample size is regarded as sufficient to provide an understanding of the safety profile of 
mRNA-1893 and to confirm the dose selection to advance development into future studies.  
Approximately 800 participants will be randomly assigned in a 1:1:1:1 ratio to receive 2 doses of 
 µg mRNA-1893 separated by 28 days (Treatment Arm A), 2 doses of 
 µg mRNA-1893 
separated by 28 days (Treatment Arm B), a single dose of 
 µg mRNA-1893 on Day 29 
following a single dose of placebo on Day 1 (Treatment Arm C), or 2 doses of placebo separated 
by 28 days (Treatment Arm D). A total of 600 participants will receive mRNA-1893, 
200 participants in each dosing arm, with approximately 100 participants in each flavivirus 
serostatus cohort and dosing arm; approximately 200 participants will receive placebo. Table 11 
presents the 95% confidence interval (CI) for 1 participant with an AE and the lowest AE rate 
detectable with at least 95% probability for each selected sample size. The 2-sided 95% CI was 
calculated using the Clopper-Pearson method for one proportion in SAS 9.4 software. A sample 
size of 200 (or 400) has at least a 95% probability to observe at least 1 participant with an AE at a 
true 1.49% (or 0.75%) AE rate. 
Table 11: 95% Confidence Interval for One Participant with an Adverse Event and the 
Lowest Detectable Incidence Rate at 95% Probability in Each Selected Sample Size 
Sample Size 
Receiving 
mRNA-1893 
Rate and 95% CI (%) at One Participant with AE 
Lowest Detectable Rate (%) 
with ≥ 95% Probability 
AE Rate 
Lower CI 
Upper CI 
100 
1.00 
0.03 
5.45 
2.95 
200 
0.50 
0.01 
2.75 
1.49 
400 
0.25 
0.01 
1.38 
0.75 
600 
0.17 
0.00 
0.93 
0.5 
Abbreviations: AE = adverse event; CI = confidence interval. 
  
For the comparison of immunogenicity, the sample size will provide adequate statistical power 
(approximately 90%) to detect a large effect size (4-fold or above in ZIKV-specific nAb titers, as 
measured by PRNT50 at Day 57) under reasonable assumptions. 
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9.3. 
Populations for Analyses 
9.3.1. 
Randomized Set 
The Randomized Set consists of all participants who are randomized in the study, regardless of the 
participant’s treatment status in the study. Participants will be included in the treatment arm to 
which they are randomized. 
9.3.2. 
Solicited Safety Set 
The Solicited Safety Set consists of all participants who are randomly assigned and received any 
IP and contribute any solicited AR data. The Solicited Safety Set will be used for the analyses of 
solicited ARs and participants will be included in the treatment arm corresponding to the IP they 
actually received. 
9.3.3. 
Safety Set 
The Safety Set consists of all participants who are randomly assigned and received any IP. The 
Safety Set will be used for analysis of safety except for the solicited ARs. Participants will be 
included in the treatment arm corresponding to the IP they actually received for the analysis of 
safety data using the Safety Set. 
9.3.4. 
Full Analysis Set 
The Full Analysis Set (FAS) consists of all participants who are randomly assigned and a) received 
any IP, b) have baseline (Day 1) data available for those analyses that require baseline data, and 
c) have at least 1 post-IP injection assessment for the analysis endpoints as specified in b). 
Participants will be included in the treatment arm to which they are randomly assigned. 
9.3.5. 
Per-Protocol Set 
The PP set consists of all FAS participants who a) comply with the vaccination schedule, 
b) comply with the timings of immunogenicity blood sampling to have post-IP injection results 
available for at least 1 assay component corresponding to the immunogenicity analysis objective, 
and c) have no major protocol deviations that impact immune response during the period 
corresponding to the immunogenicity analysis objective.  
The PP set will serve as the primary population for the analysis of immunogenicity data in this 
study. Participants will be included in the treatment arm to which they are randomly assigned. 
9.4. 
Statistical Analyses 
The statistical analysis plan (SAP) will be developed and finalized before database lock and 
treatment unblinding and will describe the analysis populations to be included in the analyses along 

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with missing handling. Analysis of exploratory endpoints will also be described in the SAP as 
appropriate. This section is a summary of the planned statistical analyses of the primary and 
secondary endpoints. 
9.4.1. 
Baseline Descriptive Statistics 
Demographic variables (eg, age, height, weight, and BMI) and baseline characteristics will be 
summarized by treatment arm overall (regardless of baseline serostatus) and by baseline flavivirus 
status assessed by dengue and West Nile specific serologies and treatment arm using descriptive 
statistics (mean, median, minimum, maximum, and standard deviation for continuous variable, 
and number and percentage for categorical variables). 
The treatment arms are: 
• mRNA-1893: 2 doses of 
 μg, separated by 28 days. 
• mRNA-1893: 2 doses 
 μg, separated by 28 days. 
• mRNA-1893: 
 μg, 1 dose on Day 29 (1 dose of placebo on Day 1). 
• Placebo: 2 doses of placebo, separated by 28 days. 
9.4.2. 
Efficacy Analyses 
Not applicable.  
9.4.3. 
Safety Analyses 
Safety analyses will include solicited ARs (local and systemic), unsolicited AEs, SAEs, AESIs, 
MAAEs, and AEs leading to vaccine/study withdrawal, and vital sign measurements. 
The intensity of solicited ARs, unsolicited AEs, and vital sign measurements will be graded as 
described in Section 11.2.8 (Appendix 2).  
All safety analyses will be based on the Safety Set, except analyses of solicited ARs which will be 
based on the Solicited Safety Set. All safety analyses will be provided by treatment arm overall 
(regardless of serostatus) and by baseline flavivirus status assessed by dengue and West Nile 
specific serologies, and vaccination (first, second), unless otherwise specified.  
Solicited local and systemic ARs during the 7-day follow-up period after each IP injection will be 
tabulated by number and percentage of participants reporting ≥ 1 event. The number and 
percentage of participants with any solicited local AR, with any solicited systemic AR, and with 
any solicited AR during the 7-day follow-up period after each IP injection will be provided with a 
2-sided 95% exact CI using the Clopper-Pearson method. 
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Unsolicited AEs will be coded according to the Medical Dictionary for Regulatory Activities 
(Dictionary for Adverse Reaction Terminology version). Unsolicited AEs, treatment-related AEs, 
SAEs, AESIs, MAAEs, and AEs leading to discontinuation from IP or participation in the study, 
severe AEs, and deaths will be reported by number and percentage of participants reporting ≥ 1 
event, and number of events. Table 12 summarizes analysis strategy for solicited AR and 
unsolicited AE parameters. 
Table 12: Analysis Strategy for Solicited Adverse Reactions and Unsolicited Adverse 
Events Parameters  
Safety Endpoint 
Descriptive Statistics 
(Number and Percentage of 
Participants)1 
95% CI2 
Any solicited AR 
X 
X 
Any unsolicited AE 
X 
 
Any unsolicited treatment-related AE 
X 
 
Any SAE 
X 
 
Any AESI 
X 
 
Any treatment-related SAE 
X 
 
Any unsolicited MAAE 
X 
 
Any unsolicited treatment-related MAAE 
X 
 
Any unsolicited AE leading to discontinuation from IP 
X 
 
Any unsolicited AE leading to discontinuation from 
participation in the study 
X 
 
Any severe unsolicited AE  
X 
 
Any severe unsolicited treatment-related AE  
X 
 
Any fatal AE 
X 
 
Abbreviations: AE = adverse event; AESI = adverse event of special interest; AR = adverse reaction; CI = confidence interval; 
IP = investigational product; MAAE = medically attended adverse event; SAE = serious adverse event. 
1 
X = results will be provided. 
2 
95% CI using the Clopper-Pearson method. 
For all other safety parameters, descriptive summary statistics will be provided. 
Further details will be described in the SAP. 
9.4.4. 
Immunogenicity Analyses 
Immunogenicity analyses will be conducted on the PP set, reported by treatment arm overall and 
by baseline flavivirus status assessed by dengue and West Nile specific serologies as applicable. 

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If the number of participants in the FAS and PP set differ by more than 10%, supportive 
immunogenicity analyses may be conducted on the FAS. 
For the primary and secondary immunogenicity endpoints, descriptive summary statistics of 
antibody-mediated immunogenicity at each time point will include GMT (for nAbs), median, 
minimum, maximum, 95% CI, and geometric mean fold rise of post-baseline/baseline nAb titers 
with corresponding 95% CI. 
For GMT calculations, 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. 
The number and percentage of participants with seroconversion will be provided with 2-sided 
95% CI using Clopper-Pearson method by treatment arm overall and by baseline flavivirus 
serostatus.  
The number and percentage of participants with seroresponse will be provided with 2-sided 
95% CI using Clopper-Pearson method by treatment arm in baseline flavivirus-seronegative 
participants. 
The number and percentage of participants with ≥ 2 or ≥ 4-fold rise in ZIKV-specific nAb titers 
will be provided with 2-sided 95% CI using the Clopper-Pearson method at each post-baseline 
timepoint. 
Seroconversion is defined as either an increase in ZIKV-specific nAb titer from below the LLOQ 
to a titer equal to or above LLOQ, or an increase of at least 4 fold in ZIKV-specific nAb titer in 
participants with pre-existing nAb titers, as measured by a specific assay/methodology. 
Seroresponse is defined as an increase in ZIKV-specific nAb titer from below the LLOQ to greater 
than or equal to the LLOQ, as measured by a specific assay/methodology. 
Further details will be described in the SAP. 
9.5. 
Study Planned Analyses  
The following analyses will be conducted on cleaned data:  
1. An IA of safety and immunogenicity data will be performed after all participants have 
completed Day 57 (28 days after the IP injection). The Day 57 IA will be performed by a 
separate team of unblinded programmers and statisticians. Pre-identified Sponsor team 
members will be unblinded to review treatment level results, as defined in the study Data 
Blinding Plan. The unblinded statistics team will not be involved in either study design or 
the regular study conduct. The participants and study sites will remain blinded until the 

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conclusion of the study. The IA will serve as the basis for the progression to the ZIKV 
Phase 3 studies. 
2. The final CSR will include full unblinded analyses of all safety and immunogenicity with 
individual unblinded listings through Day 196 (all data through approximately 6 months 
after the last IP injection).  
3. An addendum to the CSR will include the safety and immunogenicity data from Month 8 
until EOS for all participants enrolled in the Extension Period.  
More details can be found in the SAP. 
In addition, unblinded data presentation or analysis for DSMB review will be handled by the 
unblinded team of statisticians and programmers, who are not involved in study design. More 
details regarding DSMB analysis can be found in the DSMB Charter.  

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10. 
REFERENCES 
Anderson EJ, Rouphael NG, Widge AT, Jackson LA, Roberts PC, Makhene M, et al; mRNA-1273 
Study Group. Safety and immunogenicity of SARS-CoV-2 mRNA-1273 vaccine in older adults. 
N Engl J Med. 2020;383(25):2427-38. 
Aretz HT, Billingham ME, Edwards WD, Factor SM, Fallon JT, Fenoglio JJ Jr, et al. Myocarditis. 
A histopathologic definition and classification. Am J Cardiovasc Pathol. 1987;1:3-14. 
Baden LR, El Sahly HM, Essink B, Kotloff K, Frey S, Novak R, et al; COVE Study Group. 
Efficacy and safety of the mRNA-1273 SARS-CoV-2 vaccine. N Engl J Med. 2021;384(5):403-16. 
Brasil P, Pereira JP Jr, Moreira ME, Ribeiro Nogueira RM, Damasceno L, Wakimoto M, et al. 
Zika virus infection in pregnant women in Rio de Janeiro. N Engl J Med. 2016;375(24):2321-34. 
Cao-Lormeau VM, Blake A, Mons S, Lastère S, Roche C, Vanhomwegen J, et al. Guillain-Barré 
Syndrome outbreak associated with Zika virus infection in French Polynesia: a case-control study. 
Lancet. 2016;387(10027):1531-39. 
Campos GS, Bandeira AC, Sardi SI. Zika virus outbreak, Bahia, Brazil. Emerg Infect Dis. 
2015;21(10):1885-6. 
Chin J, Magoffin RL, Shearer LA, Schieble JH, Lennette EH. Field evaluation of a respiratory 
syncytial virus vaccine and a trivalent parainfluenza virus vaccine in a pediatric population. Am 
J Epidemiol 1969;89(4):449-63. 
Department of Health and Human Services (DHHS), Food and Drug Administration, Center for 
Biologics Evaluation and Research (US). Guidance for industry: Toxicity grading scale for 
healthy adult and adolescent volunteers enrolled in preventive vaccine clinical trials. 
September 2007. [cited 2019 Apr 10]. Available from: 
https://www.fda.gov/media/73679/download. 
Department of Health and Human Services (DHHS), Food and Drug Administration, Center for 
Biologics Evaluation and Research (US). Guidance document: FDA guidance on conduct of 
clinical trials of medical products during COVID-19 public health emergency. Guidance for 
industry, investigators, and institutional review boards. March 2020. Updated on June 03, 2020. 
[cited 2020 Jun 16]. Available from: https://www.fda.gov/media/136238/download. 
Department of Health and Human Services (DHHS), National Institutes of Health, National 
Institute of Allergy and Infectious Diseases, Division of AIDS (DAIDS). Table for grading the 
severity of adult and pediatric adverse events. Version 2.0. November 2014. [cited 2019 April 13]. 
Available from: https://rsc.niaid.nih.gov/sites/default/files/daids-ae-grading-table-v2-nov2014-
highlighted-changes.pdf. 

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Derraik JG, Slaney D. Notes on Zika virus – an emerging pathogen now present in the South 
Pacific. Aust N Z J Public Health. 2015;39(1):5-7. 
Duffy MR, Chen TH, Hancock WT, Powers AM, Kool JL, Lanciotti RS, et al. Zika virus outbreak 
on Yap Island, Federated States of Micronesia. N Engl J Med. 2009;360(24):2536-43. 
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. 
Fulginiti VA, Eller JJ, Downie AW, Kempe CH. Altered reactivity to measles virus: atypical 
measles in children previously immunized with inactivated measles virus vaccines. JAMA. 
1967;202(12):1075-80. 
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. 
Heymann DL, Hodgson A, Sall AA, Freedman DO, Staples JE, Althabe F, et al. Zika virus and 
microcephaly: why is this situation a PHEIC? Lancet. 2016;387(10020):719-21. 
Jackson LA, Anderson EJ, Rouphael NG, Roberts PC, Makhene M, Coler RN, et al and 
mRNA-1273 Study Group. An mRNA Vaccine against SARS-CoV-2 — Preliminary Report. 
N Engl J Med. 2020; 383(20):1920-1931. 
Mui BL, Tam YK, Jayaraman M, Ansell SM, Du X, Tam YY, et al. Influence of polyethylene 
glycol lipid desorption rates on pharmacokinetics and pharmacodynamics of siRNA lipid 
nanoparticles. Mol Ther Nucleic Acids. 2013;2(12):e139. 
Rüggeberg JU, Gold MS, Bayas JM, Blum MD, Bonhoeffer J, Friedlander S, et al; Brighton 
Collaboration Anaphylaxis Working Group. Anaphylaxis: case definition and guidelines for data 
collection, analysis, and presentation of immunization safety data. Vaccine. 2007;25(31):5675-84. 
Thomas SJ, Yoon IK. A review of Dengvaxia®: development to deployment. Hum Vaccin 
Immunother. 2019;15(10):2295-314. 
WHO: newsroom/detail [Internet]. Geneva, Switzerland: World Health Organization; 2020. WHO 
and experts prioritize vaccines, diagnostics and innovative vector control tools for Zika R&D; 
2016a [cited 2019 Apr 12]; [1 screen]. Available from: https://www.who.int/news-room/detail/09-
03-2016-who-and-experts-prioritize-vaccines-diagnostics-and-innovative-vector-control-tools-
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WHO. Dengue vaccine: WHO position paper, September 2018 – recommendations. Vaccine. 
2019;37(35):4848-9. 
WHO: publications/overview [Internet]. Geneva, Switzerland: World Health Organization; 2020. 
An R&D blueprint for action to prevent epidemics: plan of action; May 2016b [cited 
2019 Apr 12]; [48 screens]. Available from: https://www.who.int/publications/m/item/an-r-d-
blueprint-for-action-to-prevent-epidemics  
WHO: global/regions [Internet]. Geneva, Switzerland: World Health Organization; 2020. Zika 
virus disease; c2017-2019 [cited 2019 Apr 12]; [3 screens]. Available from: https://www.who.int
/emergencies/diseases/zika/en/ 
Zent O, Arras-Reiter C, Broeker M, Hennig R. Immediate allergic reactions after vaccinations – a 
post-marketing surveillance review. Eur J Pediatr. 2002;161(1):21-5. 

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11. 
SUPPORTING DOCUMENTATION AND OPERATIONAL 
CONSIDERATIONS 
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/IEC by the investigator and reviewed and 
approved by the IRB/IEC before the study is initiated. 
• Any amendments to the protocol will require IRB/IEC approval before implementation of 
changes made to the study design, except for changes necessary to eliminate an immediate 
hazard to study participants. 
• The investigator will be responsible for the following: 
− Providing written summaries of the status of the study to the IRB/IEC annually or 
more frequently in accordance with the requirements, policies, and procedures 
established by the IRB/IEC. 
− Notifying the IRB/IEC of SAEs or other significant safety findings as required by 
IRB/IEC procedures. 
− Providing oversight of the conduct of the study at the site and adherence to 
requirements of 21 CFR, ICH guidelines, the IRB/IEC, European Union regulation 
536/2014 for clinical studies (if applicable), and all other applicable local 
regulations. 
11.1.2. 
Study Monitoring  
Before an investigational site can enter a participant into the study, a representative of the Sponsor 
or its representatives will visit the investigational study site to: 
• Determine the adequacy of the facilities. 

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• 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, designated 
CRO, and the investigator. 
According to ICH GCP guideline, the Sponsor of the study is responsible for ensuring the proper 
conduct of the study with regard to protocol adherence and validity of data recorded in 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/IEC 
review, and inspection by providing direct access to the source data/documents. In addition, the 
study monitor will explain to and interpret for the investigator all regulations applicable to the 
clinical evaluation of an IP as documented in ICH guidelines. 
It is the study monitor’s responsibility to inspect the eCRFs and source documentation throughout 
the study to protect the rights of the participants; to verify adherence to the protocol; to verify 
completeness, accuracy, and consistency of the data; and to confirm adherence of study conduct 
to any local regulations. Details will be outlined in the Clinical Monitoring Plan. During the study, 
a monitor from the Sponsor or a representative will have regular contacts with the investigational 
site, for the following: 
• Provide information and support to the investigator(s). 
• Confirm that facilities remain acceptable. 
• Confirm that the investigational team is adhering to the protocol, that data are being 
accurately recorded in the eCRFs, and that IP accountability checks are being performed. 
• Perform source data verification. This includes a comparison of the data in the eCRFs with 
the participant’s medical records at the hospital or practice, and other records relevant to 
the study. This will require direct access to all original records for each participant (eg, 
clinical charts or electronic medical record system). 
• Record and report any protocol deviations not previously sent. 
• Confirm AEs and SAEs/AESIs have been properly documented in eCRFs and confirm any 
SAEs/AESIs have been forwarded to the SAE Hotline, and those SAEs/AESIs that met 
criteria for reporting have been forwarded to the IRB/IEC. 
The monitor will be available between visits if the investigator(s) or other staff needs information 
or advice. 

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11.1.3. 
Audits and Inspections  
The Sponsor, their designee(s), the IRB/IEC, or regulatory authorities will be allowed to conduct 
site visits to the investigational facilities for the purpose of monitoring or inspecting any aspect of 
the study. The investigator agrees to allow the Sponsor, their designee(s), the IRB/IEC, or 
regulatory authorities to inspect the IP storage area, IP stocks, IP records, participant charts and 
study source documents, and other records relative to study conduct.  
Authorized representatives of the Sponsor, a regulatory authority, and any IRB/IEC may visit the 
site to perform audits or inspections, including source data verification. The purpose of a Sponsor 
audit or inspection is to systematically and independently examine all study-related activities and 
documents to determine whether these activities were conducted, and data were recorded, 
analyzed, and accurately reported according to the protocol, ICH GCP E6(R2), and any applicable 
regulatory requirements. The investigator should contact the Sponsor immediately if contacted by 
a regulatory agency about an inspection. 
The Principal Investigator must obtain IRB approval for the investigation. Initial IRB approval, 
and all materials approved by the IRB for this study including the participant consent form and 
recruitment materials must be maintained by the investigator and made available for inspection. 
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 eligibility evaluation. 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.  

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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/IEC or study center. All consent documents will be approved by the 
appropriate IRB/IEC. The actual ICF used at each center may differ, depending on local 
regulations and IEC/IRB requirements. However, all versions must contain the standard 
information found in the sample ICF provided by the Sponsor. Any change to the content of the 
ICF must be approved by the Sponsor and the IEC/IRB prior to the form being used.  
If new information becomes available that may be relevant to the participant’s willingness to 
continue participation in the study, this will be communicated to him/her in a timely manner. Such 
information will be provided via a revised ICF or an addendum to the original ICF. 
The investigator or his/her representative will explain the nature of the study to the participant and 
answer all questions regarding the study. 
The investigator is responsible for ensuring that the participant fully understands the nature and 
purpose of the study. Information should be given in both oral and written form whenever possible.  
No participant should be obliged to participate in the study. Participants 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.  
Participants must be allowed sufficient time to decide whether they wish to participate.  
The participant must be made aware of and give consent to direct access to his/her source medical 
records by study monitors, auditors, the IRB/IEC, and regulatory authorities. The participant 
should be informed that such access will not violate participant confidentiality or any applicable 
regulations. The participant should also be informed that he/she is authorizing such access by 
signing the ICF.  
A copy of the ICF(s) must be provided to the participant or the participant’s legally authorized 
representative. 
The ICF will contain a separate section that addresses the use of remaining mandatory samples for 
optional exploratory research. The investigator or authorized designee will explain to each 
participant the objectives of the exploratory research. Participants will be told that they are free to 
refuse to participate and may withdraw their consent at any time and for any reason during the 
storage period. A separate signature will be required to document a participant's agreement to allow 

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any remaining specimens to be used for exploratory research. Participants who decline to 
participate in this optional research will not provide this separate signature. 
At Visit 10 (Day 196), all participants will have the opportunity to provide their consent to 
participate in the Extension Period (through Day 700). 
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. 
Institutional review board approval is required prior to the implementation of an amendment, 
unless overriding safety reasons warrant immediate action, in which case the IRB(s)/IEC(s) will 
be promptly notified. 
Any modifications to the protocol or the ICF, which may impact the conduct of the study, potential 
benefit of the study, or may affect participant safety, including changes of study objectives, study 
design, participant population, sample sizes, study procedures, or significant administrative 
aspects will require a formal amendment to the protocol. Such amendment will be released by the 
Sponsor, agreed by the investigator(s), and approved by the relevant IRB(s)/IEC(s) prior to 
implementation. A signed and dated statement that the protocol, any subsequent relevant amended 
documents and the ICF have been approved by relevant IRB(s)/IEC(s) must be provided to the 
Sponsor before the study is initiated. 
Administrative changes of the protocol are minor corrections and/or clarifications that have no 
effect on the way the study is to be conducted. These administrative changes will be released by 
the Sponsor, agreed by the investigator(s), and notified to the IRB(s)/IEC(s). 
11.1.8. 
Protocol Violations and Deviations  
The investigator or designee must document and explain in the participant’s source documentation 
any deviation from the approved protocol. The investigator may implement a deviation from, or a 
change to, the protocol to eliminate an immediate hazard to study participants without prior IRB 
approval. As soon as possible after such an occurrence, the implemented deviation or change, the 
reasons for it, and any proposed protocol amendments should be submitted to the IRB for review 
and approval, to the Sponsor for agreement, and to the regulatory authorities, if required.  
A deviation from the protocol is an unintended or unanticipated departure from the procedures or 
processes approved by the Sponsor and the IRB and agreed to by the investigator. Deviations 
usually have an impact on individual participants or a small group of participants and do not 

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involve inclusion/exclusion or primary endpoint criteria. A protocol violation occurs when the 
participant or investigator does not adhere to the protocol, resulting in a significant additional risk 
to the participant. Protocol violations can include nonadherence to inclusion or exclusion criteria, 
enrollment of the participant without prior Sponsor approval, or nonadherence to FDA regulations 
or ICH E6(R2) guidelines.  
Protocol violations and deviations will be documented by the clinical monitor throughout the 
course of monitoring visits. The investigator will be notified in writing by the monitor of violations 
and deviations. The IRB should be notified of all protocol violations and deviations, if appropriate, 
in a timely manner. 
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 which would make the participant identifiable will not be transferred. 
The participant must be informed that his/her personal study-related data will be used by the 
Sponsor in accordance with local data protection law. The level of disclosure must also be 
explained to the participant. 
The participant must be informed that his/her medical records may be examined by Clinical 
Quality Assurance auditors or other authorized personnel appointed by the Sponsor, by appropriate 
IRB/IEC members, and by inspectors from regulatory authorities. 
Individual participant medical information obtained as a result of this study is considered 
confidential, and disclosure to third parties is prohibited. Information will be accessible to 
authorized parties or personnel only. Medical information may be given to the participant’s 
physician or to other appropriate medical personnel responsible for the participant’s well-being. 
Each participant will be asked to complete a form allowing the investigator to notify the 
participant’s primary healthcare provider of his/her participation in this study.  
All laboratory specimens, evaluation forms, reports, and other records will be identified in a 
manner designed to maintain participant confidentiality. All records will be kept in a secure 
storage area with limited access. Clinical information will not be released without the written 
permission of the participant, except as necessary for monitoring and auditing by the Sponsor, 
its designee, relevant regulatory authority, or the IRB. 
The investigator and all employees and coworkers involved with this study may not disclose or use 
for any purpose other than performance of the study, any data, record, or other unpublished, 
confidential information disclosed to those individuals for the purpose of the study. Prior written 

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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 
Samples may be used for purposes related to ZIKV research, in particular assay development, 
assay validation, and animal challenge studies. There will be no human genetic testing (whole 
genome sequencing or creation of cell lines) performed on these samples. The DNA of the CMI 
subset participants may be used to further characterize the immune response to mRNA-1893 
vaccine, but only epitopes relevant to the ZIKV-specific immune response will be investigated. 
The samples may be stored for 20 years or until the study team has determined that specimens are 
no longer needed, per local requirements. In addition, identifiable samples can be destroyed at any 
time at the request of the participant. 

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11.1.11. 
Study Safety Oversight by Oversight Safety Team and Data Safety Monitoring 
Board  
Study safety will be monitored by an OST that will include the investigators participating in the 
study and the protocol team, which will include the CRO Medical Monitor and the Sponsor 
Clinical Development Physician and may include additional representatives from the Sponsor 
Project Team. The CRO Medical Monitor will be responsible for performing a review of the 
enrollment and study-related safety data with oversight by the Sponsor Clinical Development 
Physician. During the Vaccination Period, a formal biweekly meeting/teleconference will be 
scheduled among the CRO Medical Monitor, the Sponsor Clinical Development Physician, and 
the Lead Investigator (or alternate investigator) to review safety events in a blinded fashion. Once 
all participants in all treatment arms enter the Follow-Up Period, the interval of these meetings 
may be extended to monthly. This decision will be confirmed by the protocol team.  
In addition, an independent DSMB will be established for Study mRNA-1893-P201. It will be 
composed of experts with experience in clinical development and vaccines and with expertise in 
flaviviruses. Members of the DSMB will be independent from the study conduct and free of 
conflict of interest. The DSMB will convene on an approximately quarterly basis until study end. 
Additionally, the DSMB may convene at any time if there is an ad-hoc safety concern detected by 
the protocol team. This independent board will be informed of the progress and conduct of the 
study; their primary responsibility will be to review unblinded study data to evaluate the safety 
findings. All AEs, SAEs, AESIs, and MAAEs will be reviewed by the board, and they will be 
asked to provide recommendations and guidance as to management of safety follow-up within the 
study. In addition, should immunogenicity findings request further opinion, the DSMB would be 
asked to review unblinded available immunogenicity data and provide guidance.  
Details regarding the composition, responsibilities, and procedures of the OST and the DSMB will 
be presented in the OST and DSMB charters, respectively. 
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), etc., as well as some 
national registries. 

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In addition, results from clinical studies are required to be submitted to peer-reviewed journals 
following internal company review for accuracy, fair balance, and intellectual property. For those 
journals that request sharing of the analyzable data sets that are reported in the publication, 
interested researchers are directed to submit their request to clinicalstudydatarequest.com. 
Individual participant data and supporting clinical documents are available for request at 
clinicalstudydatarequest.com. While making information available the privacy of participants in 
clinical studies sponsored by the Sponsor is assured. Details on data sharing criteria and process 
for requesting access can be found at this web address: clinicalstudydatarequest.com. 
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/IEC review, and 
regulatory agency inspections and provide direct access to source data documents. 
• Monitoring details describing strategy (eg, risk-based initiatives in operations and quality 
such as Risk Management and Mitigation Strategies and Analytical Risk-Based 
Monitoring), methods, responsibilities and requirements, including handling of 
noncompliance issues and monitoring techniques (central, remote, or on-site monitoring) 
are provided in the 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 

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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 2 years after study completion unless local regulations 
or institutional policies require a longer retention period. No records may be destroyed 
during the retention period without the written approval of the Sponsor. No records may 
be transferred to another location or party without written notification to the Sponsor. 
Quality assurance (QA) includes all the planned and systematic actions that are established to 
ensure that the clinical study is performed and the data are generated, documented (recorded), and 
reported according to ICH GCP and local/regional regulatory standards. 
A QA representative from the Sponsor or its qualified designee, who is independent of and 
separated from routine monitoring, may periodically arrange inspections/audits of the clinical 
study by reviewing the data obtained and procedural aspects. These inspections may include 
on-site inspections/audits and source data checks. Direct access to source documents is required 
for the purpose of these periodic inspections/audits.  
11.1.14. 
Data Collection and Management  
This study will be conducted in compliance with the ICH document “Guidance for Industry-
E6 (R2) Good Clinical Practice: Consolidated Guidance,” dated November 2016. This study will 
also be conducted in accordance with the most recent version of the Declaration of Helsinki.  
This study will use electronic data collection to collect data directly from the investigational site 
using eCRFs. The investigator is responsible for ensuring that all sections of each eCRF are 
completed promptly and correctly and that entries can be verified against any source data.  
Study monitors will perform source document verification to identify inconsistencies between the 
eCRFs and source documents. Discrepancies will be resolved in accordance with the principles of 
GCP. Detailed study monitoring procedures are provided in the Clinical Monitoring Plan.  
Adverse events will be coded according to the Medical Dictionary for Regulatory Activities. 
Concomitant medications will be coded using the WHO – Drug Reference List.  
11.1.15. 
Source Documents 
Source documents are original documents or certified copies, and include, but are not limited to, 
diary cards, 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. 

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Data reported on the paper case report form or entered into 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, 
clinic, 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. 
11.1.17. 
Study and Site Closure 
If the study is prematurely terminated or suspended, the Sponsor shall promptly inform the 
investigators, the IECs/IRBs, the regulatory authorities, and any CRO(s) used in the study of the 
reason for termination or suspension, as specified by the applicable regulatory requirements. The 
investigator shall promptly inform the participant and should assure appropriate participant therapy 
and/or follow-up. 
The Sponsor or designee reserves the right to close the study site or terminate the study at any time 
for any reason at the sole discretion of the Sponsor.  
The investigator may initiate study site closure at any time, provided there is reasonable cause and 
sufficient notice is given in advance of the intended termination.  
Reasons for the early closure of a study site by the Sponsor or investigator may include but are not 
limited to: 

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• Continuation of the study represents a significant medical risk to participants. 
• Failure of the investigator to comply with the protocol, the requirements of the IRB/IEC or 
local health authorities, the Sponsor's procedures, or GCP guidelines. 
• Inadequate recruitment of participants by the investigator. 
• Discontinuation of further mRNA-1893 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: Adverse Events: Definitions and Procedures for 
Recording, Evaluating, Follow-Up, and Reporting 
11.2.1. 
Definition of an AE 
AE Definition 
• 
An AE is any untoward medical occurrence associated with the use of a drug in humans, 
regardless of whether it is considered drug related. 
• 
A treatment-emergent AE is defined as any event not present before exposure to the IP or any 
event already present that worsens in intensity or frequency after exposure to the IP. 
An AR is any AE for which there is a reasonable possibility that the IP caused the AE (Section 11.2.3). 
For the purposes of investigational new drug safety reporting, “reasonable possibility” means that there 
is evidence to suggest a causal relationship between the IP and the AE.  
An unsolicited AE is any AE reported by the participant that is not specified as a solicited AR in the 
protocol or is specified as a solicited AR in the protocol but starts outside the protocol-defined 
post-injection period for reporting solicited ARs (ie, for the 7 days after each IP injection). 
 
Events Meeting the AE Definition 
• 
Exacerbation of a chronic or intermittent pre-existing condition including either an increase in 
frequency and/or intensity of the condition. 
• 
New conditions detected or diagnosed after the first dose of IP even though they may have 
been present before the start of the study. 
 
Events NOT Meeting the AE Definition 
• 
Medical or surgical procedure (eg, endoscopy, appendectomy): the condition that leads to the 
procedure should be the AE. 
• 
Situations in which an untoward medical occurrence did not occur (social and/or convenience 
admission to a hospital). 
 
11.2.2. 
Definition of an SAE 
If an event is not an AE per definition above, then it cannot be an SAE even if serious conditions 
are met (eg, hospitalization for signs/symptoms of the disease under study, death due to 
progression of disease). 
An AE is considered “serious” if, in the view of either the investigator or the Sponsor, it results in 
any of the following outcomes (21 CFR 312.32(a)): 
 

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An SAE is defined as any untoward medical occurrence that, at any dose: 
a. 
Results in 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, regardless of whether it is 
considered IP related. 
b. 
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 might have 
caused death if it had occurred in a more severe form. 
c. 
Requires inpatient hospitalization or prolongation of existing hospitalization 
In general, hospitalization indicates that the participant was admitted to the hospital or emergency ward 
for at least one overnight stay for observation and/or treatment that would not have been appropriate in 
the physician’s office or outpatient setting. The hospital or emergency ward admission should be 
considered an SAE regardless of whether opinions differ as to the necessity of the admission. 
Complications that occur during hospitalization will be recorded as AEs; however, if a 
complication/AE prolongs hospitalization or otherwise fulfills the SAE criteria, the complication/AE 
will be recorded as a separate SAE.  
d. 
Results in significant incapacity disability/incapacity 
• 
The term disability means a substantial disruption of a person’s 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. 
e. 
Is a congenital anomaly/birth defect 
f. 
Is a 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 may require medical 
or surgical intervention to prevent one of the other outcomes listed in the above definition. 
These events should usually be considered serious. 
Examples of such events include allergic bronchospasm requiring intensive treatment in an 
emergency room or at home, blood dyscrasias or convulsions that do not result in 
hospitalization, or development of drug dependency or drug abuse. 
 

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If an event meets any of the above definitions, regardless of the severity or relationship of the event 
to the study product, the event must be reported to the Sponsor as described in Section 8.6. 
11.2.3. 
Definition of Solicited Adverse Reactions 
The occurrence and intensity of selected signs and symptoms is actively solicited from the 
participant during a specified post-IP injection period (day of injection and 6 subsequent days), 
using a pre-defined checklist in the eDiary (ie, solicited ARs; Section 8.5.1). 
The following local (injection site) ARs will be solicited: pain, erythema (redness), 
swelling/induration (hardness).  
The following systemic ARs will be solicited: headache, fatigue, myalgia (muscle aches all over 
the body), arthralgia (aching in several joints), nausea/vomiting, body temperature (potentially 
fever), and chills. 
The study site staff will contact the participant within 24 hours of becoming aware of the event in 
case a severe (Grade 3) local or systemic AR occurs within 7 days after IP injection. 
The investigator will review, confirm, and grade reactogenicity according to the grading scales 
presented in Table 13 (Section 11.2.8), Toxicity Grading Scale for Healthy Adult and Adolescent 
Volunteers Enrolled in Preventive Vaccine Clinical Trials (DHHS 2007). 
If a solicited local or systemic AR continues beyond 7 days after an injection, the participant will 
be prompted to capture the solicited local or systemic AR in the eDiary until it is no longer 
reported, not to exceed 28 days after each injection (Section 8.5.1). Solicited adverse reactions 
recorded in eDiaries beyond Day 7 should be reviewed either via telephone call (Section 8.5.2) or 
at the following study visit.  
All solicited local ARs will be considered causally related to vaccination.  
Note: Any solicited AR that meets any of the following criteria must be entered into the 
participants’ source document and must also be recorded by the study site on the Reactogenicity 
page of the participant’s eCRF: 
• Solicited local or systemic AR that results in a visit to a healthcare practitioner (MAAE; 
Section 11.2.4). 
• Solicited local or systemic AR that leads 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 an injection. 

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• Solicited local or systemic AR that leads to participant withdrawal from IP. 
• Solicited local or systemic AR that otherwise meets the definition of an SAE 
(Section 11.2.2). 
• Solicited AR with a toxicity score of Grade 3 or greater. 
11.2.4. 
Definition of Medically Attended Adverse Events 
An MAAE is an AE that leads to an unscheduled visit to a healthcare practitioner. This would 
include visits to study site for unscheduled assessments and visits to healthcare practitioners 
external to the study site (eg, urgent care, primary care physician). Investigators will review 
unsolicited AEs for the occurrence of any MAAEs. Unsolicited AEs (ie, MAAEs) will be captured 
on the AE page of the eCRF.  
11.2.5. 
Definition of 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 
Section 11.2.13 (Appendix 2). 
11.2.6. 
Recording and Follow-Up of an AE and/or SAE 
The participants will be instructed to contact the investigator immediately should they develop any 
untoward signs or symptoms or any medical condition that leads to hospitalization or an 
emergency room visit. In addition, the study site staff will contact the participant within 24 hours 
of becoming aware of the event if any of the following is reported via eDiary within 7 days after 
IP injection: severe (Grade 3) local or systemic ARs (Table 13). 
When an AE/SAE occurs, it is the responsibility of the investigator to review all documentation 
(eg, hospital progress notes, laboratory reports, and diagnostics reports) related to the event. 
The investigator will then record all relevant AE/SAE information in the eCRF in standard medical 
terminology, along with the date and time of onset and the date and time of resolution. 
It is not acceptable for the investigator to send photocopies of the participant’s medical records to 
the Sponsor or designee in lieu of completion of the AE/SAE page of the eCRF. 
There may be instances when copies of medical records for certain cases are requested by the 
Sponsor or designee. In this case, all participant identifiers, with the exception of the participant 

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number, will be redacted on the copies of the medical records before submission to the Sponsor or 
designee. 
The investigator will attempt to establish a single diagnosis of the event based on signs, symptoms, 
and/or other clinical information. Whenever possible, the diagnosis (not the individual 
signs/symptoms) will be documented as the AE/SAE. Each AE is to be evaluated for duration, 
severity, seriousness, and relatedness to mRNA-1893. 
11.2.7. 
Pregnancy 
Pregnancies occurring in participants after enrollment must be reported to Sponsor or designee 
within 72 hours of the site learning of its occurrence (Section 11.3.3). 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 the 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 
(Section 11.2.11). 
11.2.8. 
Assessment of Severity 
The severity (or intensity) of an AE refers to the extent to which it affects the participant’s daily 
activities. The Toxicity Grading Scale for Healthy Adult and Adolescent Volunteers Enrolled in 
Preventive Vaccine Clinical Trials (DHHS 2007), presented in Table 13 will be used to record the 
intensity of solicited ARs and vital sign measurements observed during this study. 
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.  
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 

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AE that fluctuates in severity during the course of the event is reported once in the eCRF at the 
highest severity observed. 
Table 13: Toxicity Grading  
Local Reaction to 
Injectable Product 
 
None 
(Grade 0) 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially 
Life-threatening 
(Grade 4a) 
Pain at injection site 
 
 
None 
Does not 
interfere with 
activity 
Repeated use 
of over-the-
counter pain 
reliever > 24 
hours or 
interferes with 
activity 
Any use of 
prescription 
pain reliever 
or prevents 
daily activity 
ER visit or 
hospitalization 
Injection site 
Erythema/Redness* 
 
<2.5 cm 
2.5 – 5 cm 
5.1 – 10 cm 
> 10 cm 
Necrosis or 
exfoliative 
dermatitis 
Injection site 
Induration/Swelling** 
 
<2.5 cm 
2.5 – 5 cm and 
does not 
interfere with 
activity 
5.1 – 10 cm or 
interferes with 
activity 
> 10 cm or 
prevents daily 
activity 
Necrosis 
a Grading for Grade 4 events per investigator assessment (with the exception of fever). 
Abbreviation: AE = adverse event; eCRF = electronic case report form; ER = emergency room. 
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. 
*  
In addition to grading the measured local reaction at the greatest single diameter, the measurement should be recorded as a 
continuous variable.  
** Induration/swelling should be evaluated and graded using the functional scale as well as the actual measurement. 
Source: Guidance for Industry – Toxicity Grading Scale for Heathy Adult and Adolescent Volunteers Enrolled in Preventive 
Vaccine Clinical Trials; Tables for Clinical Abnormalities (DHHS 2007). 

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Systemic (General) 
 
None 
(Grade 0) 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially 
Life-threatening 
(Grade 4a) 
Fever (°C)* 
(°F)* 
< 38.0°C 
< 100.4°F 
38.0 – 38.4 
100.4 – 101.1 
38.5 – 38.9 
101.2 – 102.0 
39.0 – 40 
102.1 – 104 
> 40 
> 104 
Nausea/Vomiting  
 
None 
No 
interference 
with activity or 
1 to 
2 episodes/ 
24 hours 
Some 
interference 
with activity or 
> 2 episodes/ 
24 hours 
Prevents 
daily 
activity, 
requires 
outpatient IV 
hydration 
ER visit or 
hospitalization 
for hypotensive 
shock 
Chills 
 
 
None 
No 
interference 
with activity 
Some 
interference 
with activity 
not requiring 
medical 
attention 
Prevents 
daily activity 
and requires 
medical 
intervention 
ER visit or 
hospitalization 
Headache  
 
 
 
None 
 
No 
interference 
with activity 
Repeated use 
of over-the-
counter pain 
reliever 
> 24 hours or 
some 
interference 
with activity 
Significant; 
any use of 
prescription 
pain reliever 
or prevents 
daily activity 
ER visit or 
hospitalization 
Fatigue 
 
None 
No 
interference 
with activity 
Some 
interference 
with activity 
Significant; 
prevents 
daily activity 
ER visit or 
hospitalization 
Myalgia (muscle aches 
all over body)  
 
None 
No 
interference 
with activity 
Some 
interference 
with activity 
Significant; 
prevents 
daily activity 
ER visit or 
hospitalization 
Arthralgia (joint aches 
in several joints)  
 
 
None 
No 
interference 
with activity 
Some 
interference 
with activity 
not requiring 
medical 
intervention 
Prevents 
daily activity 
and requires 
medical 
intervention 
ER visit or 
hospitalization 
a. 
Grading for Grade 4 events per investigator assessment (with exception of fever). 
Abbreviations: AE = adverse event; eCRF = electronic case report form; ER = emergency room; IV = intravenous. 
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. 
* Oral temperature; no recent hot or cold beverages or smoking. 
Sources: Guidance for Industry – Toxicity Grading scale for Heathy Adult and Adolescent Volunteers Enrolled in Preventive 
Vaccine Clinical Trials; Tables for Clinical Abnormalities (DHHS 2007). Division of AIDS Grading the Severity of Adult and 
Pediatric Adverse Events (DHHS 2014). 
 
 
 

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Table 14:    Table for Clinical Abnormalities 
 
Vital Sign* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially 
Life-threatening 
(Grade 4) 
Tachycardia (beats per 
minute) 
101 – 115 
116 – 130 
> 130 
ER visit or 
hospitalization 
for arrhythmia 
Bradycardia (beats per 
minute)** 
50 – 54 
45 – 49 
< 45 
ER visit or 
hospitalization 
for arrhythmia 
Hypertension (systolic) 
(mm Hg) 
141 – 150 
151 – 155 
> 155 
ER visit or 
hospitalization 
for malignant 
hypertension 
Hypertension (diastolic) 
(mm Hg) 
91 – 95 
96 – 100 
> 100 
ER visit or 
hospitalization 
for malignant 
hypertension 
Hypotension (systolic) 
(mm Hg)  
85 – 89 
80 – 84 
< 80 
ER visit or 
hospitalization 
for hypotensive 
shock 
Respiratory rate (breaths 
per minute) 
17 – 20 
21 – 25 
> 25 
Intubation 
Abbreviation: ER = emergency room. 
Note that fever is classified under systemic reactions for grading purposes. 
* Participant should be at rest for all vital sign measurements.  
** When resting heart rate is between 60 – 100 beats per minute. Use clinical judgment when characterizing bradycardia 
among some healthy participant populations, for example, conditioned athletes. 
Source: Guidance for Industry – Toxicity Grading Scale for Heathy Adult and Adolescent Volunteers Enrolled in Preventive 
Vaccine Clinical Trials; Tables for Clinical Abnormalities (DHHS 2007). 
11.2.9. 
Assessment of Causality 
Assessment of Causality 
All solicited injection site ARs are considered to be related to IP. 
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. The causality assessment 
between the solicited systemic ARs/unsolicited AEs and mRNA-1893 exposure is one of the criteria 
used when determining regulatory reporting requirements. For each solicited systemic 
AR/unsolicited AE, the investigator will assess causality (ie, whether there is a reasonable 
possibility that the IP caused the event) according to the categories below:  

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Not Related: There is not a reasonable possibility of a relationship to the IP. Participant did not 
receive the IP, or temporal sequence of the AE onset relative to administration of the IP is not 
reasonable, or the AE is more likely explained by another cause than the IP. 
Related: There is 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. 
Assessment of Expectedness 
• 
An AE or solicited AR is considered “unexpected” if it is not listed in the IB or is not listed at 
the specificity or severity that has been observed with the vaccine being tested or, if an IB is not 
required or available, it is not consistent with the risk information described in the general 
investigational plan or elsewhere in the current application. For example, under this definition, 
hepatic necrosis would be unexpected (by virtue of greater severity) if the IB referred only to 
elevated hepatic enzymes or hepatitis. Similarly, cerebral thromboembolism and cerebral 
vasculitis would be unexpected (by virtue of greater specificity) if the IB listed only cerebral 
vascular accidents. “Unexpected,” as used in this definition, also refers to AEs or suspected ARs 
that are mentioned in the IB as occurring with a class of drugs or as anticipated from the 
pharmacological properties of the drug but are not specifically mentioned as occurring with the 
particular drug under investigation. 
11.2.10. 
Follow-Up of AEs and SAEs 
Follow-Up of AEs and SAEs 
• 
All AEs, SAEs, and MAAEs must be reported in detail on the appropriate page of the eCRF 
and followed until the event is resolved or stable or judged by the investigator to be not 
clinically significant. 
11.2.11. 
Reporting of SAEs 
Any AE considered serious by the investigator or that meets SAE criteria (Section 11.2.2) must be 
reported to the Sponsor immediately (within 24 hours of becoming aware of the SAE). The 
investigator will assess whether there is a reasonable possibility that the IP caused the SAE. The 
Sponsor will be responsible for notifying the relevant regulatory authorities of any SAE as outlined 
in the 21 CFR Parts 312 and 320. The investigator is responsible for notifying the IRB directly.  
 

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SAE Reporting to the Sponsor or Designee via an Electronic Data Collection Tool 
• 
The primary mechanism for reporting an SAE to designee will be the electronic data collection 
tool. 
• 
If the electronic system is unavailable, then the site will use the paper SAE data collection tool 
(see next section) in order to report the event within 24 hours of becoming aware of the event. 
• 
The site will enter the SAE data into the electronic system as soon as it becomes available. 
• 
After the study is completed at a given site, the electronic data collection tool will be taken 
off-line to prevent the entry of new data or changes to existing data. 
• 
If a site receives a report of a new SAE from a study participant or receives updated data on a 
previously reported SAE after the electronic data collection tool has been taken off-line, then 
the site can report this information on a paper SAE form (see next section) or using the 
following contact information: 
 
o SAE Mailbox: 
 
o SAE Hotline (USA and Canada): 
 
 
SAE Reporting to the Sponsor or Designee via Paper Case Report Form 
• 
A backup plan is used (using a paper SAE form) when the eCRF system does not work and 
should be faxed to the Sponsor at:  
o SAE Fax line (USA and Canada): 
 
• 
In rare circumstances and in the absence of facsimile equipment, notification by telephone is 
acceptable with a copy of the SAE data collection tool sent by overnight mail or courier 
service. 
• 
Initial notification via telephone does not replace the need for the investigator to complete and 
sign the SAE case report form pages within the designated reporting time frames. 
 
 
 
 
 
 
 
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11.2.12. 
Reporting of AESIs 
The process for reporting an AESI ensures compliance with 21 CFR 312 and ICH GCP guidelines. 
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 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. 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. If the AESI meets the criteria 
for an SAE, the SAE reporting procedure should be followed. 
11.2.13. 
Adverse Events of Special Interest Terms 
Investigators should report all events that fall into the categories presented in Table 15 as an AESI 
per the reporting processes in Section 11.2.12. These AESIs are medical concepts that are generally 
of interest in vaccine safety surveillance as per the Brighton Collaboration and Safety Platform for 
Emergency Vaccines. 
Table 15:    Adverse Events of Special Interest 
Medical Concept 
Additional Notes 
Thrombocytopenia 
• Platelet counts < 150 × 109  
• Including but not limited to immune 
thrombocytopenia, platelet production decreased, 
thrombocytopenia, thrombocytopenic purpura, 
thrombotic thrombocytopenic purpura, or 
hemolysis, elevated liver enzymes, and low platelet 
count (HELLP) syndrome 
New onset of or worsening of the 
following neurologic diseases: 
• Guillain-Barré Syndrome 
• Acute disseminated encephalomyelitis (ADEM) 
• Idiopathic peripheral facial nerve palsy (Bell’s 
palsy) 
• Seizures including but not limited to febrile 
seizures and/or generalized seizures/convulsions 

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Medical Concept 
Additional Notes 
Anaphylaxis 
• Anaphylaxis as defined per Section 11.2.13.2 
• Follow reporting procedures in Section 11.2.12 
Myocarditis/Pericarditis 
• Myocarditis 
• Pericarditis 
• Myopericarditis 
• Refer to Section 11.2.13.1 for details. 
 
11.2.13.1. 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 
should also be reported as an SAE if it meets seriousness criteria (Section 11.2.2). The CDC case 
definition is provided in Section 11.4 (Appendix 4) as guidance. 
11.2.13.2. Anaphylaxis 
All suspected cases of anaphylaxis should be recorded as an AESI 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 11.2.11. The Investigator will submit any updated anaphylaxis case 
data to the Sponsor within 24 hours of it being available. For reporting purposes, a participant who 
displays signs or symptoms consistent with anaphylaxis (as 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: 

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− 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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11.3. 
APPENDIX 3: Contraceptive Guidance and Collection of Pregnancy 
Information 
11.3.1. 
Definitions: Women of Childbearing Potential 
Females of childbearing potential are those who are considered fertile following menarche and 
until becoming postmenopausal unless permanently sterile (see below). If fertility is unclear (eg, 
amenorrhea in adolescents or athletes) and a menstrual cycle cannot be confirmed before first dose 
of mRNA-1893, additional evaluation should be considered. 
Women in the following categories are not considered women of childbearing potential: 
1. Premenarchal. 
2. Premenopausal, surgically sterile female with one of the following: 
a. Documented complete hysterectomy. 
b. Documented bilateral salpingectomy. 
c. Documented bilateral oophorectomy. 
For individuals with permanent infertility due to an alternate medical cause other than the above, 
(eg, müllerian agenesis, androgen insensitivity), investigator discretion should be applied to 
determining study entry. 
Note: Documentation can come from the site personnel’s review of the participant’s medical 
records, medical examination, or medical history interview. 
3. Postmenopausal female. 
• A postmenopausal state is defined as no menses for 12 months without an alternative 
medical cause. The following age-specific requirements apply:  
o Women < 50 years of age would be considered postmenopausal if they have been 
amenorrheic for 12 months or more following cessation of exogenous hormonal 
treatments and if they have luteinizing hormone and FSH levels in the 
postmenopausal range for the institution. 
o Women ≥ 50 years of age would be considered postmenopausal if they have been 
amenorrheic for 12 months or more following cessation of all exogenous 
hormonal treatments, had radiation-induced menopause with last menses > 1 year 
ago, had chemotherapy-induced menopause with last menses > 1 year ago. 
• A high FSH level in the postmenopausal range may be used to confirm a 
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replacement therapy (HRT). However, in the absence of 12 months of amenorrhea, 
confirmation with more than one FSH measurement is required.  
• Females on HRT and whose menopausal status is in doubt will be required to use one 
of the non-estrogen hormonal highly effective contraception methods if they wish to 
continue their HRT during the study. Otherwise, they must discontinue HRT to allow 
confirmation of postmenopausal status before study enrollment. 
11.3.2. 
Contraception Guidance: 
Female participants must be nonpregnant and nonlactating and meet one of the following 
criteria:  
a. Postmenopausal (defined as amenorrhea for 12 consecutive months without an 
alternative medical cause or documented serum FSH level in the postmenopausal 
range);  
b. Surgically sterile (hysterectomy, bilateral tubal ligation, or bilateral oophorectomy).  
NOTE: Procedures and laboratory results must be confirmed in the medical record, by 
physical examination, or by official written confirmation of a procedure; or  
c. If of childbearing potential, has practiced adequate contraception or has abstained from 
all activities that could result in pregnancy for at least 28 days prior to the first 
vaccination (Day 1) and agrees to consistently use a highly effective (ie, < 1% failure 
rate per year) method of contraception (Table 16) through 3 months after the last IP 
injection. Female participants should also refrain from breastfeeding throughout this 
period. 

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Table 16: Highly Effective Methods of Contraception (< 1% Failure Rate) 
Barrier/Intrauterine Methods 
Hormonal Methods 
Copper T intrauterine device 
Levonorgestrel-releasing intrauterine system (eg, 
Mirena®)1 
 
Implants: Etonogestrel-releasing implants (eg, 
Implanon®) or levonorgestrel-releasing implant (eg, 
Norplant®) 
Intravaginal Devices: Ethinylestradiol/etonogestrel-
releasing intravaginal devices: eg, NuvaRing®  
Injection: Medroxyprogesterone injection: eg, Depo-
Provera®  
Combined Pill: Normal and low dose combined oral 
contraceptive pill 
Patch: Norelgestromin/ethinylestradiol-releasing 
transdermal system: eg, Ortho Evra® 
Mini pill: Progesterone-based oral contraceptive pill 
using desogestrel: Cerazette® is currently the only 
highly effective progesterone-based pill 
1 
This is also considered a hormonal method. 
 
11.3.3. 
Collection of Pregnancy Information 
Pregnancies occurring in participants after enrollment must be reported to Sponsor or designee 
within 24 hours of the site learning of its occurrence. 
Female Participants Who Become Pregnant 
• The investigator will collect pregnancy information on any female participant who 
becomes pregnant while participating in this study. Information will be recorded on the 
appropriate form and submitted to the Sponsor within 72 hours of learning of a participant's 
pregnancy.  
• The participant will be followed to determine the outcome of the pregnancy (including 
spontaneous miscarriage, elective termination, normal birth, or congenital abnormality). 
The investigator will collect follow-up information on the participant and the child, even 
if the participant is discontinued from the study, and the information will be forwarded to 
the Sponsor. Generally, follow-up will not be required for longer than 6 to 8 weeks beyond 
the estimated delivery date. Any termination of pregnancy will be reported, regardless of 
fetal status (presence or absence of anomalies) or indication for the procedure. 
• While pregnancy itself is not considered to be an AE or SAE, any pregnancy complication 
or elective termination of a pregnancy will be reported as an AE or SAE. Spontaneous 
miscarriages, congenital anomaly, and/or birth defect abortion should be reported as SAEs.  

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• Any post-study, pregnancy-related SAE considered reasonably related to the mRNA-1893 
by the investigator will be reported to the Sponsor as described in Section 7.1. While the 
investigator is not obligated to actively seek this information in former study participants, 
he or she may learn of an SAE through spontaneous reporting. 
Any female participant who becomes pregnant while participating in the study will discontinue 
mRNA-1893 or be withdrawn from the study. 

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

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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 
11.5.1. 
Amendment 2 (27 Oct 2021) 
11.5.2. 
Amendment 1 (16 Sep 2021) 
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CCI

Signature Page for VV-CLIN-003500 v4.0
Signature Page for VV-CLIN-003500 v4.0
Approval
10-Dec-2021 19:45:47 GMT+0000
PPD