A Phase 3 Safety, Immunogenicity, and Lot-Consistency Trial of the VLP-Based Chikungunya Vaccine PXVX0317 in Healthy Adults and Adolescents
Phase: PHASE3
Conditions: Chikungunya Virus
Sponsor: Bavarian Nordic

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 1 of 80 
CLINICAL STUDY PROTOCOL 
A Phase 3 Safety, Immunogenicity, and Lot-Consistency Trial of the 
VLP-Based Chikungunya Vaccine PXVX0317 in Healthy Adults and 
Adolescents 
EBSI-CV-317-004 
Version 5.0 
20 Mar 2023 
ClinicalTrials.gov ID: NCT05072080 
Sponsor: 
Emergent Travel Health Inc. 
CONFIDENTIAL 
This document is a confidential communication of the sponsor. Acceptance of this document 
constitutes an agreement by the recipient that no unpublished information contained within 
will be published or disclosed without prior written approval, except that this document may 
be disclosed to the appropriate Ethics Committee and Regulatory Authority under the 
condition that they keep it confidential.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 2 of 80 
DOCUMENT HISTORY 
Version 
Date 
Description of Change 
Brief Rationale 
1.0 
24Aug2020 
Initial version of protocol 
N/A 
2.0 
06Jul2021 
Added Day 15 Visit 
Added hierarchical testing to 
statistical section 
Inclusion of Day 15 Visit to have a more 
robust immunogenicity assessment 
Hierarchical testing added to control 
type I error for FDA primary endpoints 
and seroresponse secondary endpoint at 
Days 15, 183, and 8 
3.0 
10Nov2021 
Updated MM 
Updated Inclusion Criteria 
Updated labeling section. 
Change in study personnel 
Clarified Inclusion Criteria regarding 
acceptable contraception for adolescents 
and adults in same-sex relationships 
Modified to better align with ICH 
E6(R2) GCP and Emergent’s updated 
protocol template 
4.0 
10Feb2022 
Updated Exclusion Criteria 11 
Added a purpose statement 
Added HCV RNA testing if HCV 
antibody is positive 
Definition of medically attended 
visits was clarified. 
Edited from 30 days prior to Screening 
to Day 1 as it was incorrect in previous 
versions of the protocol 
To align with ICH E6(R2) GCP 
Clarification per memo to Investigators 
sent 10Jan2022 
Clarified that routine scheduled study 
visits were not considered medically 
attended visits. 
5.0 
See effective 
date 
Study objectives and endpoints – 
coprimary objectives and 
immunogenicity endpoints have been 
updated and key secondary endpoints 
with associated success criteria were 
added. 
Added 
EMA definition of seroresponse rate 
as the presumptive seroprotection 
rate. Added success criterion of 
lower bound of the two-sided 95% CI 
on the seroresponse rate difference 
 at Day 15. 
Removed the drug product 
composition table. 
Added the use of paper diaries 
Updated “CHIKV-luc assay anti-
CHIKV SNA NT80” to “human SNA 
assay” 
Simplification for global use of the 
protocol. 
To align with FDA and EMA feedback 
received 26Jul2022 and 25Jan2023, 
respectively. 
To align with company position to refer 
to the IB rather than share product 
composition in the protocol. 
To use as a back-up to the e-diary if the 
e-diary is not available.
Per response to FDA IR dated
17Mar2022 Regarding Assay Validation

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 3 of 80 
Updated “Alhydrogel” to aluminum 
hydroxide” 
Reports and Non-Human Primate 
Passive Transfer Study 
Updated terminology. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 4 of 80 
SPONSOR SIGNATORY 
Signatory: 
See electronic signature at end of document. 
Date (DDMMMYYYY) 
KEY STUDY CONTACT INFORMATION 
Sponsor’s Medical Monitor (MM): 
Immediately Reportable Adverse Events: 
Emergent Global Pharmacovigilance 
For all other contact information refer to study contact list. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 5 of 80 
INVESTIGATOR SIGNATORY 
Compliance Statement: This study is to be conducted in accordance with the ethical 
principles that originate from the Declaration of Helsinki and that are consistent with 
International Council for Harmonization of Technical Requirements for Pharmaceuticals for 
Human Use (ICH) Good Clinical Practice (GCP) guidelines and regulatory requirements, as 
applicable. 
EBSI-CV-317-004, Version 5.0: 
A Phase 3 Safety, Immunogenicity, and Lot-
Consistency Trial of the VLP-Based 
Chikungunya Vaccine PXVX0317 in Healthy 
Adults and Adolescents 
Clinical Site(s): 
Institution Name: 
Institution Address: 
My signature below verifies that I have read and agree to this protocol. I am aware of my 
responsibilities as an investigator under the current ICH GCP guidelines, the Declaration of 
Helsinki, United States of America (US) Food and Drug Administration (FDA) Code of 
Federal Regulations (CFRs) and state and local regulations and applicable laws and 
regulations of the country of the study site for which I am responsible. I agree to conduct the 
study according to these regulations. 
I have read this protocol in its entirety and agree to conduct this study accordingly. Any 
changes in procedure will only be made if necessary, to protect the safety, rights, and welfare 
of study participants. 
I agree to conduct in person and/or to supervise staff assigned to specific study 
responsibilities. I will ensure that all staff who assist me in the conduct of the study have 
access to the protocol and all pertinent information. I will ensure that all assigned staff are 
trained and qualified and are fully informed of their responsibilities regarding the conduct of 
the study. 
I agree to abide by the terms of the confidentiality disclosure agreement and/or contract with 
the sponsor and/or its representatives. 
Site Principal 
Investigator: 
Principal Investigator Name (print) 
Title (print) 
Principal Investigator Signature 
Date (DDMMMYYYY) 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 6 of 80 
PROTOCOL SYNOPSIS 
Name of Sponsor/Company:  Emergent Travel Health Inc. 
Name of Investigational Product:  PXVX0317 
Name of Active Ingredient(s):  Chikungunya virus virus-like particle (CHIKV VLP) 
Protocol Number: EBSI-CV-317-004 
Title of Study: A Phase 3 Safety, Immunogenicity, and Lot-Consistency Trial of the VLP-
Based Chikungunya Vaccine PXVX0317 in Healthy Adults and Adolescents 
Study Centers: Multicenter, up to 50 sites in the US 
Study Duration for One Participant: 7 months 
Estimated Study Duration: ~12 months  
Phase of Development: 3 
Coprimary Objectives: 
•
To evaluate the safety of PXVX0317 in healthy adult and adolescent participants
12 to <65 years of age.
•
To compare the anti-CHIKV serum neutralizing antibody (SNA) response to
PXVX0317 and placebo at Day 22, as measured by geometric mean titer (GMT)
and clinically relevant difference in seroresponse rate (PXVX0317 minus placebo).
Note: Seroresponse rate (considered the presumptive seroprotection rate) is defined as 
the percentage of participants who achieve an anti-CHIKV SNA 
 See 
Section 6.1 for assay description. 
•
To demonstrate the consistency of the anti-CHIKV SNA response across three
consecutively manufactured lots of PXVX0317 at Day 22 as measured by GMT.
Secondary Objectives: 
•
To compare the anti-CHIKV SNA response to PXVX0317 and placebo at Day 15,
Day 183, and Day 8, as measured by GMT and seroresponse rate.
•
To compare the anti-CHIKV SNA response to PXVX0317 and placebo in
participants 12 to <18 years of age, participants 18 to <46 years of age, and
participants 46 to <65 years of age as measured by GMT and seroresponse rate.
Exploratory Objective: 
•
To evaluate anti-CHIKV SNA response across three consecutively manufactured
lots of PXVX0317 as measured by seroresponse rate for each lot at Day 22 in
participants 18 to <46 years of age.
Methodology/Study Design: 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 7 of 80 
This is a phase 3, randomized, placebo-controlled, double-blind, parallel-group design 
with four treatment groups. Participants will be randomized in a 2:2:2:1 ratio within each 
age stratum (12 to <18, 18 to <46, and 46 to <65) to receive one of three consecutively 
manufactured lots of PXVX0317 or placebo. With 3150 participants enrolled, the 
treatment group totals are estimated as follows: 
•
Group 1- PXVX0317 lot A: n=900
•
Group 2- PXVX0317 lot B: n=900
•
Group 3- PXVX0317 lot C: n=900
•
Group 4- Placebo: n=450
A nested lot consistency substudy will be performed in adult participants 18 to <46 years 
of age in the PXVX0317 treatment groups (lot A, lot B, and lot C). 
Procedures and Assessments: 
Study procedures and assessments will occur at: Screening (Visit 1), to occur no more than 
30 days prior to Day 1 of investigational product (IP) administration; Day 1 (Visit 2, 
baseline, randomization, and administration of IP); Day 8 (Visit 3); Day 15 (Visit 4); Day 
22 (Visit 5); Day 29 (Visit 6, via telephone contact); Day 92 (Visit 7, via telephone 
contact); Day 183 (Visit 8, End of Study) or; Early Discontinuation Visit. The per 
participant estimated total study duration is 212 days.  
Solicited adverse events (AEs collected from IP administration on Day 1 through Day 8) 
will consist of local (injection site pain, redness, and swelling) and systemic (fever, chills, 
fatigue, headache, myalgia, arthralgia, and nausea) reactions. Unsolicited AEs will be 
collected from Day 1 through Day 29. Serious adverse events (SAEs), adverse events of 
special interest (AESI), and medically attended adverse events (MAAE) will be collected 
from Day 1 through to the Day 183 End of Study Visit. An independent Safety Monitoring 
Committee (SMC) will review aggregated, blinded safety data after the 300th enrolled 
participant passes Day 29, and again after the last enrolled participant passes Day 29. 
The induction of the humoral immune response (immunogenicity) by PXVX0317 vaccine, 
specifically anti-CHIKV SNA titers, will be measured by a bioluminescence assay 
developed by the sponsor that uses a modified version of CHIKV containing a reporter 
gene that expresses a luciferase protein (CHIKV-luc) in infected Vero cells in vitro. 
Reduction of luciferase activity (ie, reduced bioluminescence) occurs in infected cultures 
of cells following treatment of CHIKV-luc with test serum containing anti-CHIKV SNA. 
The quantitation of reporter gene expression, a correlate of the level of virus infection of 
cells, is determined by detection of luciferase using a microplate luminometer. The anti-
CHIKV SNA titer 80 (NT80) is the reciprocal of the serum dilution that provides 80% 
protection of Vero cells from CHIKV-luc infection or an 80% reduction of luciferase 
activity compared to virus only control. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 8 of 80 
The levels of anti-CHIKV SNA will be determined for time points up to 182 days after 
dosing (Day 183 End of Study Visit).  
Number of Participants (Planned): At least 3150 
Study Population: Healthy adult and adolescent participants 12 to <65 years of age 
Criteria for Study Participation 
Inclusion Criteria:  
Participants must meet all the following criteria to be enrolled: 
1. Able and willing to provide informed consent (and assent, as applicable)
voluntarily signed by participant (and guardian, as applicable).
2. Males or females, 12 to <65 years of age.
3. Generally healthy, in the opinion of the investigator, based on medical history,
physical examination, and screening laboratory assessments.
4. Women who are either:
i.
Not of childbearing potential (CBP): pre-menarche, surgically sterile (at
least six weeks post bilateral tubal ligation, bilateral oophorectomy or
hysterectomy), or postmenopausal (defined as a history of ≥12 consecutive
months without menses prior to randomization in the absence of other
pathologic or physiologic causes, following cessation of exogenous
sex-hormonal treatment).
or: 
ii.
Meeting all the below criteria:
•
Negative serum pregnancy test at Screening Visit
•
Negative urine pregnancy test immediately prior to dosing at Day 1
•
Use one of these acceptable methods of contraception (if women of CBP)
for the duration of participation:
•
Hormonal contraceptives (eg, implants, pills, patches) initiated ≥30 days
prior to dosing
•
Intrauterine device (IUD) inserted ≥30 days prior to dosing
•
Double barrier type of birth control (male condom with female
diaphragm, male condom with cervical cap)
•
Abstinence is acceptable only for adolescents (12 to <18 years old)
who are not sexually active.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 9 of 80 
Note: See Section 3.3.7 for this study’s list of acceptable method of contraception. 
Note: Contraception requirements do not apply for participants in exclusively same-sex 
relationships and these participants should have no plans to become pregnant by any other 
means for the duration of the study. 
Exclusion Criteria:  
Participants who meet any of the following criteria cannot be enrolled: 
1. Currently pregnant, breastfeeding, or planning to become pregnant during the
study.
2. Body Mass Index (BMI) ≥35 kg/m2.
3. Positive laboratory evidence of current infection with human immunodeficiency
virus (HIV-1, HIV-2), hepatitis C virus (HCV) or hepatitis B virus (HBV).
4. History of severe allergic reaction or anaphylaxis to any component of the IP.
5. History of any known congenital or acquired immunodeficiency that could impact
response to vaccination (eg, leukemia, lymphoma, generalized malignancy,
functional or anatomic asplenia, alcoholic cirrhosis).
6. Prior receipt or anticipated use of systemic immunomodulatory or
immunosuppressive medications from six months prior to screening through Day
22. Note: For systemic corticosteroids, use at a dose or equivalent dose of 20 mg of
prednisone daily for 14 days or more within three months of screening through Day
22 is exclusionary. The use of inhaled, intranasal, topical, ocular, or intraocular
steroids is allowed.
7. Receipt or anticipated receipt of blood or blood-derived products from 90 days
prior to screening through Day 22.
8. Acute disease within the last 14 days (participants with an acute mild febrile illness
can be considered for a deferral of vaccination two weeks after the illness has
resolved and treatment has been completed).
9. Clinically significant cardiac, pulmonary, rheumatologic, or other chronic disease,
in the opinion of the investigator. This may include chronic illness requiring
hospitalization in the last 30 days prior to screening.
10. Enrollment in an interventional study and/or receipt of another investigational
product from 30 days prior to screening through the duration of study participation.
11. Receipt or anticipated receipt of any vaccine from 30 days prior to Day 1 through
Day 22.
12. Evidence of substance abuse that, in the opinion of the investigator, could
adversely impact the participant’s participation or the conduct of the study.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 10 of 80 
13. Prior receipt of an investigational CHIKV vaccine/product.
14. Any other medical condition that, in the opinion of the investigator, could
adversely impact the participant’s participation or the conduct of the study.
Investigational Product, Dosage, and Mode of Administration: 
PXVX0317 vaccine is comprised of CHIKV VLP 40 µg, aluminum hydroxide 
(Alhydrogel®) 2% adjuvant, and formulation buffer supplied as a single dose of 0.8 mL in 
a pre-filled syringe administered via intramuscular (IM) injection in the deltoid muscle. 
Reference Therapy, Dosage and Mode of Administration: 
Placebo is comprised of formulation buffer supplied as a single dose of 0.8 mL in a 
pre-filled syringe administered via IM injection in the deltoid muscle. 
Criteria for Evaluation 
Primary Endpoints: 
Safety Endpoints: 
•
Incidence of solicited AEs through Day 8 for PXVX0317 and placebo.
•
Incidence of unsolicited AEs through Day 29 for PXVX0317 and placebo.
•
Incidence of AESI, MAAEs, and SAEs, through Day 183 for PXVX0317 and
placebo.
Coprimary Immunogenicity Endpoints: 
•
Difference in anti-CHIKV SNA seroresponse rate (PXVX0317 minus placebo) and
associated 95% confidence interval (CI) at Day 22.
Note: Seroresponse rate (considered the presumptive seroprotection rate) is defined as 
the percentage of participants who achieve an anti-CHIKV SNA 
 See 
Section 6.1 for assay description. See Section 8.6 for immunogenicity analysis details 
and Section 8.6.2.5 for success criteria and multiplicity controls. 
•
Anti-CHIKV SNA GMT and associated 95% CIs at Day 22 for PXVX0317 and
placebo.
•
Anti-CHIKV SNA GMT ratio between all three pairs of PXVX0317 lots (A:B,
A:C, B:C) (adults 18 to <46 years of age) at Day 22.
Secondary Endpoints: 
•
Key Secondary Endpoints: Difference in anti-CHIKV SNA seroresponse rate
(PXVX0317 minus placebo) with associated 95% CIs at Day 15, Day 183, and Day
8, in that order (see Section 8.6.2.5).

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 11 of 80 
•
Anti-CHIKV SNA GMTs by study arm with associated 95% CIs at Day 8, Day 15,
and Day 183.
•
Geometric mean fold increase (GMFI) from Day 1 to subsequent collection time
points.
•
Number and percentage of participants with an anti-CHIKV SNA titer ≥15 and
4-fold rise over baseline.
Exploratory Endpoints: 
•
Anti-CHIKV SNA seroresponse rate difference with associated 95% CIs for each
pair of PXVX0317 lots (A minus B, A minus C, B minus C) (adults 18 to <46
years of age) at Day 22.
Statistical Methods 
Sample Size Considerations: 
The primary statistical comparison between the PXVX0317 and placebo treatment groups 
is based on difference between treatment groups in seroresponse rate (proportion of 
participants with CHIKV-luc assay anti-CHIKV SNA NT80 [human SNA assay] 
 at 
Day 22.  
Based on the data from the phase 2 study (protocol PXVX-CV-317-001), the seroresponse 
rate for PXVX0317 vaccine is expected to be approximately 
 vs <5% for the placebo 
participants. With an assumed 10% rate of non-evaluable participants, the power to show 
superiority over placebo with 2430 PXVX0317 vaccine and 405 placebo evaluable 
participants is >99.9% for the combined age groups. The power is 99% for each of the 
smaller 12 to <18 and 46 to <65 age groups with samples sizes of 210 vs 35 evaluable 
participants (PXVX0317: placebo).  
The difference in seroresponse rate between PXVX0317 and placebo groups that is 
considered clinically relevant is 
. With 2430 PXVX0317-treated participants and a 
target seroresponse rate of 
 vs a rate of 0% for placebo, the width of a two-sided 95% 
CI would be ±1.2%. The difference in seroresponse rate must be above 
 for the lower 
bound of the 95% CI for the difference to be 
. 
The second consideration for sizing the study is ensuring adequate power for the lot 
consistency equivalence intervals testing immunogenicity at Day 22, as measured by 
human SNA assay GMT ratios between all three pairs of consecutively manufactured 
PXVX0317 lots (A:B, A:C, B:C) in the 18 to <46 years of age stratum for the 
immunogenicity evaluable population (IEP). For all three pairwise GMT ratios, the two-
sided 95% CI must fall within [0.667, 1.5] for the lots to be considered equivalent.  
On the log10 scale, two one-sided equivalence tests have 95% power to reject the null 
hypothesis that the difference in mean titers between lots is below -0.176 or above 0.176 in 
favor of an alternative hypothesis of equivalence when the expected difference in log10 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 12 of 80 
means is 0, the common standard deviation (SD) is 0.455, each test is at the 2.5% level and 
the sample size in each lot is 207. The SD estimate is based on the upper bound of an 80% 
CI on the SD on the log10 scale observed in the human SNA assay on samples collected 4 
weeks after participants were treated with a single dose of PXVX0317. To be conservative, 
at least 1050 evaluable participants (300 participants administered PXVX0317 from each 
lot and 150 participants administered placebos) need to be enrolled into the 18 to <46 age 
group to provide adequate power for the lot consistency objective.   
The final consideration for the sample size of the study is the size of the prelicensure 
safety database. With 2700 participants receiving any lot of PXVX0317, this study is 
93.3% likely to detect at least one AE with a true frequency of ≥0.1% (ie, “uncommon”). 
Analysis 
Safety: 
All safety analyses will be based on the safety population. The three PXVX0317 lots will 
be combined in the tabulations and each of the safety analyses will be summarized across 
all ages and repeated for three (12 to <18, 18 to <46, and 46 to <65) participant age 
groups. Incidences of local (ie, injection site pain, redness, and swelling) and systemic 
reactions (ie, fever, chills, fatigue, headache, myalgia, arthralgia, and nausea) occurring 
from IP administration on Day 1 through Day 8 will be summarized by maximum severity 
and by treatment group. Unsolicited AEs will also be summarized by maximum severity 
and treatment group according to Medical Dictionary of Regulatory Activities (MedDRA) 
by system organ class (SOC) and preferred terms (PT). 
Superiority to Placebo at Day 22: 
The proportion of participants in each treatment group (PXVX0317 and placebo) with 
seroresponse at titer 
 will be computed, along with the two-sided 95% CI. This 
analysis will be primarily based the IEP and repeated for the modified intent-to-treat 
(mITT) population as a measure of the robustness of the findings. The significance of the 
treatment group difference will be assessed using a chi-square test, based on the response 
across all age groups combined, with an alpha=0.05. The significance of the difference in 
seroresponse rates between treatment groups for each age cohort will also be determined. 
The difference in seroresponse rates between the two groups will be calculated, along with 
the 95% CI for the difference based on the Newcombe hybrid score method. The lower 
bound of the two-sided 95% CI on the difference in seroresponse rates between 
PXVX0317 and placebo must be 
 to satisfy the primary objective to demonstrate a 
clinically relevant seroresponse. Differences in seroresponse rates between the two groups 
will be tested similarly at Days 15, 183, and 8, in that order (see Section 8.6.2.5). 
Day 22 GMTs will be compared between PXVX0317 and placebo treatment groups and 
will be analyzed via a linear model based on a two-sided alpha=0.05. The primary model is 
an analysis of variance (ANOVA), with logarithmically transformed anti-CHIKV SNA 
titers (log10) as the dependent variable and treatment group and study site as the fixed 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 13 of 80 
effects in the model. The adjusted least square means and their 95% CIs calculated based 
on the ANOVA will be back transformed and reported as the group GMT values.  
Lot Consistency: 
For all three pairs of lots (A:B, A:C, and B:C), the two-sided 95% CI for the ratio of anti-
CHIKV SNA GMTs at Day 22 in PXVX0317-treated participants ages 18 to <46 will be 
computed. The 95% CI must be contained within the [0.667; 1.5] interval for the lots to be 
considered equivalent. This analysis will be based on the IEP. The analyses will also be 
run for the mITT population as a measure of the robustness of the results.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 14 of 80 
SCHEDULE OF EVENTS 
Screening 
Visit 1 
Day 1 
Visit 2 
Day 8 
Visit 3 
Day 15 
Visit 4 
Day 22 
Visit 5 
Day 29 
Visit 6 
(Phone) 
Day 92 
Visit 7 
(Phone) 
Day 18313 
Visit 8 
Window (days) 
Within 30 days 
of Day 1 
-1/+3
-1/+3
-1/+3
±1 
±3 
-14/+7
Informed Consent/Assent 
X 
Eligibility Criteria 
X 
*X
Medical History 
X1 
*X2
Demography 
X 
Physical Exam 
X3 
*X4
X4 
X4 
X4 
X4 
Viral Marker testing (HIV-1/2, anti-HCV5, 
HBsAg) 
X 
Urine Toxicology6 
X 
Vital Signs7 
X 
*X8
Pregnancy Test (female of CBP) 
X9 
*X10
FSH Levels (post-menopausal female) 
X 
Randomization 
*X
Administration of Investigational Product 
X 
Acute Observation 
X 
Solicited AEs 
X
X 
Unsolicited AEs 
X 
X 
X 
X 
X 
SAEs 
X 
X 
X 
X 
X 
X 
X 
AESI 
X 
X 
X 
X 
X 
X 
X 
MAAE 
X 
X 
X 
X 
X 
X 
X 
Concomitant Medications 
X 
X 
X 
X 
X 
X 
X11 
X11 
Anti-CHIKV SNA Sample 
*X
X 
X 
X 
X 
e-Diary Training and Distribution of Devices12
X 
e-Diary Collection and Review
X 
*To be done prior to IP administration.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 15 of 80 
FSH = follicle stimulating hormone 
1To include presence of joint pain. 
2To be updated if necessary. 
3Complete physical exam. 
4Directed physical exam, as needed. 
5If HCV antibody is positive HCV ribonucleic acid (RNA) testing can be performed.
6Urine toxicology, per investigator’s discretion. 
7To include height and body weight (for BMI calculation). 
8To be taken before and after IP administration. 
9Serum pregnancy test. 
10Urine pregnancy test. 
11Concomitant medications associated with SAE/AESI/MAAE only. 
12Smart phone (e-diary), digital thermometer, and ruler. 
13Early Discontinuation/Withdrawal Visit occurring within 7 days postvaccination, from 7 to 21 days postvaccination, or ≥22 days postvaccination the Visit 3, Visit 5, 
or Visit 8 schedule will be followed respectively.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 16 of 80 
TABLE OF CONTENTS 
1 
BACKGROUND INFORMATION ............................................................................23 
1.1 
Name and Description of Investigational Product ............................................23 
1.2 
Chikungunya Virus and Disease Background ..................................................23 
1.3 
Justification for Use of Investigational PXVX0317 Vaccine ............................24 
1.3.1 
Summary of Animal Studies ...............................................................................25 
1.3.2 
Summary of Findings from Clinical Studies ......................................................26 
1.3.3 
Seroresponse Rate ...............................................................................................28 
1.3.4 
Rationale for Dosage and Route of Administration ............................................28 
1.4 
Justification for Inclusion of Adolescents 12 to <18 Years of Age ..................28 
2 
STUDY OBJECTIVES AND PURPOSE ...................................................................29 
2.1 
Purpose..................................................................................................................29 
2.2 
Coprimary Objectives .........................................................................................29 
2.3 
Secondary Objectives...........................................................................................30 
2.4 
Exploratory Objective .........................................................................................30 
3 
STUDY DESIGN ...........................................................................................................30 
3.1 
Study Description .................................................................................................30 
3.1.1 
Study Centers ......................................................................................................30 
3.1.2 
Number of Participants (Planned) .......................................................................31 
3.1.3 
Estimated Study Duration ...................................................................................31 
3.2 
Schematic Diagram of Study Design ..................................................................32 
3.3 
Description of Study Assessments ......................................................................33 
3.3.1 
Review of Eligibility Criteria..............................................................................33 
3.3.2 
Medical History and Demography ......................................................................33 
3.3.3 
Physical Examination..........................................................................................33 
3.3.4 
Vital Signs ...........................................................................................................33 
3.3.5 
Laboratory Tests .................................................................................................34 
3.3.6 
Immunogenicity Sample .....................................................................................34 
3.3.7 
Pregnancy Testing and Contraception ................................................................34 
3.3.8 
Investigational Product Administration ..............................................................35 
3.3.9 
Acute Observation After Investigational Product Administration......................35 
3.3.10 Solicited Adverse Events ....................................................................................35 
3.3.11 Unsolicited Adverse Events ................................................................................36 
3.3.12 Serious Adverse Events and Adverse Events of Special Interest .......................36 
3.4 
Measures Taken to Minimize/Avoid Bias ..........................................................36 
3.4.1 
Treatment Assignment/Randomization ..............................................................36 
3.4.2 
Masking/Blinding Procedures .............................................................................37 
3.5 
End of Study .........................................................................................................37 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 17 of 80 
4 
SELECTION AND WITHDRAWAL OF PARTICIPANTS ...................................38 
4.1 
Inclusion Criteria .................................................................................................38 
4.2 
Exclusion Criteria ................................................................................................39 
4.3 
Withdrawal of Participants .................................................................................40 
4.3.1 
Participant Consent Withdrawal .........................................................................40 
4.3.2 
Investigator-Based Participant Withdrawal ........................................................40 
4.3.3 
Follow-up for Withdrawn Participants ...............................................................40 
4.3.4 
Documentation of Withdrawal/Discontinuation .................................................41 
4.3.5 
Participant Replacement .....................................................................................41 
5 
TREATMENT OF PARTICIPANTS .........................................................................41 
5.1 
Investigational Products ......................................................................................41 
5.1.1 
PXVX0317 Vaccine............................................................................................41 
5.1.2 
Placebo Pre-filled Syringe ..................................................................................42 
5.1.3 
Labeling ..............................................................................................................42 
5.1.4 
Investigational Product Shipment .......................................................................42 
5.1.5 
Storage Conditions ..............................................................................................43 
5.1.6 
Preparation ..........................................................................................................43 
5.1.7 
Drug Accountability............................................................................................43 
5.2 
Study Procedures and Assessments by Visit .....................................................43 
5.2.1 
Screening (Visit 1, within 30 days of Day 1)......................................................43 
5.2.2 
Day 1 (Baseline, Randomization, and Administration of IP) Visit 2 .................45 
5.2.3 
Day 8 (-1/+3) Visit 3 ...........................................................................................45 
5.2.4 
Day 15 (-1/+3) Visit 4 .........................................................................................46 
5.2.5 
Day 22 (-1/+3) Visit 5 .........................................................................................46 
5.2.6 
Day 29 (±1) Telephone Contact for Visit 6 ........................................................46 
5.2.7 
Day 92 (±3) Telephone Contact for Visit 7 ........................................................46 
5.2.8 
Day 183 (-14/+7) Visit 8 End of Study ...............................................................46 
5.2.9 
Early Discontinuation/Withdrawal Visit.............................................................46 
5.2.10 Unscheduled Visits .............................................................................................47 
5.3 
Prior and Concomitant Medications ..................................................................47 
5.3.1 
Required Concomitant Medications ...................................................................47 
5.4 
Procedures for Monitoring Participant Compliance ........................................47 
6 
IMMUNOGENICITY ASSESSMENT .......................................................................47 
6.1 
Immunogenicity Analysis ....................................................................................47 
7 
SAFETY ASSESSMENTS AND REPORTING ........................................................48 
7.1 
Definitions .............................................................................................................48 
7.1.1 
Adverse Event .....................................................................................................48 
7.1.2 
Solicited Adverse Event ......................................................................................48 
7.1.3 
Unsolicited Adverse Event .................................................................................49 
7.1.4 
Adverse Event of Special Interest .......................................................................49 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 18 of 80 
7.1.5 
Serious Adverse Event ........................................................................................49 
7.1.6 
Suspected Unexpected Serious Adverse Reaction ..............................................50 
7.1.7 
Severity of Adverse Events .................................................................................50 
7.1.8 
Causality of Adverse Events ...............................................................................50 
7.2 
Eliciting Adverse Events......................................................................................51 
7.3 
Reporting Requirements for Immediately Reportable Events ........................51 
7.3.1 
Principal Investigator’s Reporting Requirements ...............................................51 
7.3.2 
Sponsor’s Reporting Requirements ....................................................................52 
7.4 
Reporting of Other Information - Unanticipated Problems ............................52 
7.5 
Follow-up of Adverse Events ..............................................................................53 
7.5.1 
Follow-up of Nonserious Adverse Events ..........................................................53 
7.5.2 
Follow-up of Serious Adverse Events or Adverse Events of Special 
Interest.................................................................................................................54 
7.6 
Safety Data Monitoring .......................................................................................54 
7.7 
Breaking the Blind for Individual Participants ................................................54 
8 
STATISTICAL CONSIDERATIONS ........................................................................55 
8.1 
Sample Size Rationale..........................................................................................55 
8.1.1 
Sample Size and Power for Immunogenicity ......................................................55 
8.1.2 
Sample Size and Power for Lot Consistency ......................................................56 
8.1.3 
Sample Size and Power for Adverse Events .......................................................56 
8.2 
Analysis Populations ............................................................................................56 
8.3 
Study Endpoints ...................................................................................................57 
8.3.1 
Primary Endpoints ..............................................................................................57 
8.3.2 
Secondary Endpoints ..........................................................................................58 
8.3.3 
Exploratory Endpoint ..........................................................................................58 
8.4 
Handling Missing Data ........................................................................................58 
8.5 
Analysis of Disposition, Demographic and Baseline Characteristics ..............58 
8.6 
Immunogenicity Analysis ....................................................................................59 
8.6.1 
Coprimary Immunogenicity Analysis .................................................................59 
8.6.2 
Secondary Immunogenicity Analysis .................................................................61 
8.7 
Safety Analysis .....................................................................................................62 
8.7.1 
Exposure .............................................................................................................63 
8.7.2 
Adverse Events ...................................................................................................63 
8.7.3 
Clinical Laboratory Data.....................................................................................65 
8.7.4 
Physical Examinations ........................................................................................65 
8.7.5 
Vital Signs ...........................................................................................................65 
8.7.6 
Prior and Concomitant Medications ...................................................................65 
8.7.7 
Other Safety Variables ........................................................................................65 
8.7.8 
Subgroup Analysis ..............................................................................................65 
8.7.9 
Interim Analysis ..................................................................................................65 
9 
DATA HANDLING AND RECORD KEEPING .......................................................65 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 19 of 80 
9.1 
Source Documents and Access ............................................................................65 
9.2 
Data Management ................................................................................................66 
9.3 
Data Collection and Discrepancy Management ................................................66 
9.4 
Laboratory Data...................................................................................................67 
9.5 
File Management at the Investigational Site .....................................................67 
9.6 
Records Retention at the Investigational Site ...................................................67 
9.7 
Deviations from the Protocol ..............................................................................67 
10 
QUALITY CONTROL AND ASSURANCE..............................................................68 
10.1 
Monitoring ............................................................................................................68 
10.2 
Auditing ................................................................................................................68 
11 
ETHICS AND RESPONSIBILITY .............................................................................69 
11.1 
Informed Consent/Assent ....................................................................................69 
11.2 
Institutional Review Board .................................................................................69 
11.3 
Compensation for Injury .....................................................................................70 
11.4 
Participant Confidentiality .................................................................................70 
11.5 
Future Use of Stored Samples .............................................................................70 
12 
ADMINISTRATIVE AND LEGAL REQUIREMENTS ..........................................71 
12.1 
Sponsorship ..........................................................................................................71 
12.2 
Protocol Amendments .........................................................................................71 
12.3 
Clinical Study Registration .................................................................................71 
12.4 
Publication Policy.................................................................................................71 
12.5 
Terminating the Study .........................................................................................72 
12.6 
Terminating the Study at an Individual Site .....................................................72 
13 
REFERENCES ..............................................................................................................72 
APPENDIX 
APPENDIX I 
TOXICITY GRADING SCALE TABLES .........................................76 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 20 of 80 
LIST OF TABLES 
Table 1 
Needle Length of Intramuscular Injections for Children (by Age) and Adults 
Aged ≥19 Years (By Sex and Weight) ...............................................................35 
LIST OF FIGURES 
Figure 1 
Chikungunya Virus Global Burden ....................................................................24 
Figure 2 
EBSI-CV-317-004 Schematic Diagram of Study Design...................................32 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 21 of 80 
LIST OF ABBREVIATIONS 
ACIP 
Advisory Committee on Immunization Practices 
AE 
Adverse Event  
AESI 
Adverse Event of Special Interest 
ANOVA 
Analysis of Variance  
BMI 
Body Mass Index 
C 
Capsid 
CBP 
Childbearing Potential 
CDC 
US Centers for Disease Control and Prevention 
CFR 
Code of Federal Regulations 
CHIKV 
Chikungunya Virus  
CI 
Confidence Interval  
DMP 
Data Management Plan  
E 
Envelope  
eCRF 
Electronic Case Report Form  
EDC 
Electronic Data Capture  
EMA 
European Medicines Agency 
FDA 
US Food and Drug Administration  
FSH 
Follicle Stimulating Hormone 
GCP 
Good Clinical Practice  
GMFI 
Geometric Mean Fold Increase 
GMT 
Geometric Mean Titer  
HBV 
Hepatitis B Virus  
HCV 
Hepatitis C Virus  
HEK 
Human Embryonic Kidney 
HIV 
Human Immunodeficiency Virus  
IB 
Investigator’s Brochure 
IC 
Inhibitory Concentration 
ICF 
Informed Consent Form  
ICH 
International Council on Harmonization  
IEP 
Immunogenicity Evaluable Population 
IgG 
Immunoglobulin G 
IM 
Intramuscular  
IND 
Investigational New Drug  
IP 
Investigational Product 
IRB 
Institutional Review Board  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 22 of 80 
IUD 
Intrauterine Device 
LLOQ 
Lower Limit of Quantitation 
MAAE 
Medically Attended Adverse Event 
MedDRA 
Medical Dictionary of Regulatory Activities  
mITT 
Modified Intent-to-Treat Population 
MM 
Medical Monitor 
NHP 
Nonhuman primate 
NIH 
National Institutes of Health 
nsP 
Nonstructural Proteins 
NT 
Neutralization Titer  
PFU 
Plaque Forming Unit 
PT 
Preferred Term 
PV 
Pharmacovigilance 
RNA 
Ribonucleic Acid 
RT-qPCR 
Reverse Transcriptase Quantitative Polymerase Chain Reaction 
RTSM 
Randomization and Trial Supply Management 
SAE 
Serious Adverse Event  
SAP 
Statistical Analysis Plan  
SARS-CoV-2 
Severe Acute Respiratory Syndrome Coronavirus 2 (COVID-19) 
SD 
Standard Deviation 
SMC 
Safety Monitoring Committee 
SNA 
Serum Neutralizing Antibody 
SOC 
System Organ Class 
SR 
Seroresponse Rate 
SUSAR 
Serious and Unexpected Suspected Adverse Reactions 
VLP 
Virus-Like Particle  
VRC 
Vaccine Research Center 
US 
United States of America 
WHO 
World Health Organization  
w/w 
Weight per weight 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 23 of 80 
1 
BACKGROUND INFORMATION 
1.1 
Name and Description of Investigational Product 
PXVX0317 is a CHIKV VLP vaccine. The vaccine is comprised of CHIKV VLP adsorbed 
on aluminum hydroxide 2% adjuvant (2% (w/w) aqueous suspension of aluminum 
hydroxide) and stabilized with formulation buffer, supplied as a single dose of 0.8 mL in a 
pre-filled syringe to be administered IM in the deltoid. For additional product information, 
see Section 5.1 and the PXVX0317 Investigator’s Brochure (IB).  
The target indication for PXVX0317 vaccine is for active immunization to prevent disease 
caused by chikungunya virus. 
1.2 
Chikungunya Virus and Disease Background 
Chikungunya virus is an arthropod-borne alphavirus of the family Togaviridae. The CHIKV 
virion contains a positive-sense single-strand RNA genome with a long open reading frame 
coding for capsid (C) and envelope (E1, E2, E3, and 6K) structural proteins, together with 
four nonstructural proteins (nsP1, nsP2, nsP3, and nsP4) required for replication of the virus. 
Since the first case reports of CHIKV in a 1952-1953 outbreak in Tanzania (1), this disease 
has been endemic in Africa and parts of Asia with transmission to humans occurring through 
Aedes aegypti and more recently via Aedes albopictus mosquitoes (2). Beginning in 2014, 
CHIKV disease cases were reported among US travelers returning from affected areas in the 
Americas and local transmission was identified in Florida, Puerto Rico, and the US Virgin 
Islands. According to the US Centers for Disease Control and Prevention (CDC), 
approximately 117 countries or territories have documented cases of CHIKV infection 
excluding those countries where only imported cases have been documented (Figure 1 
adapted from (3)). Although mosquitoes are the primary mode of transmission of CHIKV, 
blood-borne transmission via needle stick is possible. Maternal-fetal transmission has been 
documented during pregnancy (4).  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 24 of 80 
Figure 1 
Chikungunya Virus Global Burden 
Following an incubation period of two to 12 days, acute clinical manifestations include high 
fever, rash, gastrointestinal complications, headache, muscle pain, nausea, fatigue, myalgia, 
and joint pain (5-7). The most classic symptom of CHIKV is a debilitating polyarthralgia that 
is present in greater than 90% of cases (8). This acute phase resolves within several weeks, 
but joint pain and arthritis may persist for months or years in over 25% to 40% of infected 
individuals (9). 
There are currently no approved vaccines to prevent CHIKV infection or disease. However, 
protection against subsequent infection has been shown to correlate with the presence of 
CHIKV serum antibodies that neutralize the virus in vitro (10, 11). 
1.3 
Justification for Use of Investigational PXVX0317 Vaccine 
The National Institutes of Health (NIH) Vaccine Research Center (VRC) initiated the 
development of the CHIKV VLP vaccine, designated VRC-CHKVLP059-00-VP. The VRC 
completed phase 1 (VRC 311) (12, 13) and phase 2 (VRC 704) (14, 15) clinical studies (14, 
15). PaxVax Inc. then manufactured the vaccine as PXVX0317, conducted a mouse 
immunogenicity study showing comparability to the VRC-CHKVLP059-00-VP vaccine, and 
proceeded to a phase 2 study (PXVX-CV-317-001) (16). PaxVax Inc. was acquired by 
Emergent BioSolutions, Inc. in October 2018, and has been renamed Emergent Travel Health 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 25 of 80 
Inc. (Emergent) as the sponsor of two phase 2 studies (PXVX-CV-317-001 (16), 
EBSI-CV-317-002 (17), and this phase 3 study (EBSI-CV-317-004).  
1.3.1 Summary of Animal Studies 
 
 
 
 
 
 
 
 
 
 
 
 
 
   
 
 
 
 
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 26 of 80 
1.3.2 Summary of Findings from Clinical Studies 
VRC 311 (NIH) 
The safety and immunogenicity of VRC-CHKVLP059-00-VP were evaluated under BB-IND 
14907 in VRC 311, a phase 1 open-label, dose-escalation study (12, 13). Healthy adult 
participants 18 to 50 years of age were assigned to sequential dose level groups to receive IM 
injections of 10 µg, 20 µg, or 40 µg (without adjuvant) on Weeks 0, 4, and 20, with 
follow-up for 44 weeks after enrollment. The primary endpoints were safety and tolerability 
of the vaccine. Secondary endpoints were CHIKV-specific immune responses assessed by 
neutralizing antibody assay and enzyme-linked immunosorbent assay (12, 13). 
All injections were well tolerated, with no SAEs reported. The most common local reaction 
was mild injection site pain (36%) and the most common systemic reaction was mild malaise 
(24%). No moderate or severe reactogenicity was observed (12, 13). 
Neutralizing antibodies were detected in all dose groups after the second vaccination. The 
GMT of the half maximum inhibitory concentration (IC50) was 2688 in the 10 µg group, 
1775 in the 20 µg group, and 7246 in the 40 µg group, and a significant boost occurred after 
the third vaccination in all dose groups (10 µg group p=0.0197, 20 µg group p<0.0001, and 
40 µg group p<0.0001). Four weeks after the third vaccination, the GMT of the IC50 was 
8745 for the 10 µg group, 4525 for the 20 µg group, and 5390 for the 40 µg group (12, 13). 
These findings were confirmed by both a plaque reduction assay and the sponsor’s 
luciferase-based assay (human SNA assay) (18), confirming both the immunogenicity of the 
VLP and the suitability of human SNA assay for future studies (see Section 6.1 for assay 
details).  
VRC 704 (NIH) 
The NIH’s VRC 704 was a phase 2 study conducted at multiple CHIKV-endemic sites in the 
Caribbean (14, 15). The study was a double-blind, placebo-controlled study with 200 
participants (planned) receiving 20 µg of CHIKV VLP and 200 participants receiving 
placebo in a two-dose series at Weeks 0 and 4. The study was initiated in 2016 and 
completed in 2018. Approximately 20% of participants demonstrated detectable CHIKV 
neutralizing antibodies at baseline using the focus reduction neutralization test reported as 
EC50 values. EC50 is the dilution of sera that inhibits 50% infection in viral neutralization 
assay. CHIKV VLP appeared safe and was well tolerated in participants who were followed 
through Week 72, with no related SAEs or other safety concerns (14, 15). CHIKV VLP 
appeared highly immunogenic, with a GMT of 2004.5 and 99.5% of recipients having 
neutralizing antibodies at Week 8. A boosting effect of SNA after administration of CHIKV 
VLP was also observed in participants with baseline CHIKV neutralizing antibodies (14, 15). 
Specimens from VRC 704 were also analyzed ad hoc by the sponsor, using the human SNA 
assay. A subgroup analysis was performed on participants without baseline CHIKV 
neutralizing activity. Using a more stringent 80% neutralization cut-off (NT80), the GMT was 
123 at Week 4 and 1701 at Week 8. After Week 8, antibody levels declined by about 1 log 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 27 of 80 
but remained elevated above baseline, with GMTs of 213 at Week 24, 115 at Week 48, and 
100 at Week 72, indicating that long-term protection can potentially be achieved without the 
need for booster dose(s). These results demonstrated that CHIKV VLP was well tolerated 
and immunogenic in adults in CHIKV-endemic areas, including those with serologic 
evidence of previous CHIKV exposure. The most frequently reported local AE was 
pain/tenderness at the injection site reported as mild by 58 of 197 (29%) vaccine recipients 
who received at least one study injection and as moderate by 3/197 vaccine recipients (2.0%). 
The most frequently reported systemic AEs were mild or moderate headache reported by 54 
of 197 (27.4%) vaccine recipients, malaise (53/197, 26.9%), and myalgia (46/197, 23.4%) 
(14, 15). Placebo recipients reported these systemic reactogenicity symptoms at similar 
frequencies. One vaccine recipient (0.5%) experienced a headache graded as severe 
following the second vaccination. A total of 16 SAEs in 15 (3.8%) participants were 
reported, all were assessed as unrelated to the IP (ie, CHIKV VLP or placebo). All 
potentially related AEs resolved without clinical sequelae (14, 15). 
Taken together, the findings from VRC 311 and VRC 704 suggest that VRC-CHKVLP059-
00-VP is well-tolerated and immunogenic in both CHIKV-exposed and CHIKV-naïve adults.
PXVX-CV-317-001 (Emergent) 
The sponsor’s phase 2 clinical study (PXVX-CV-317-001) conducted in the US compared 
multiple dose and dosing regimens of CHIKV VLP in healthy adults age 18 to <46 years 
(16). The dosages of CHIKV VLP ranged from 6 µg to 40 µg, adjuvanted. These doses were 
below or approximately equivalent to those used in the NIH’s VRC 311 (12, 13) and VRC 
704 (14, 15) clinical studies using the non-adjuvanted CHIKV VLP (VRC-CHKVLP059-00-
VP) vaccine. PXVX0317 vaccine was immunogenic across all dose groups as measured by 
human SNA assay. Immunogenicity data reported as 80% antibody NT80 values supported 
the benefit of adjuvant was evident after one dose but not two doses. There was a clear 
dose-response relationship in GMT. Participants receiving 20 µg on the standard schedule 
(Days 1 and 29), either unadjuvanted (as the NIH reference dose) or adjuvanted, had the 
highest Day 57 GMT at 1946 and 1884 respectively, similar to those of CHIKV VLP 
recipients in the VRC 704 study (14, 15). Participants receiving the single 40 µg dose 
demonstrated only slightly lower GMT levels (1712 at Day 57, i.e., 28 days after 
vaccination); all other dose groups demonstrated a GMT range of 914 to 1613 at Day 57. 
Seroconversion rates (titer ≥15) showed that with a single dose administered, up to 98% of 
study participants produced a neutralizing antibody response by Day 8. Further, the immune 
response was shown to be persistent through the 12-month visit, including in the one dose 
40 µg CHIKV VLP regimen. There was a clear dose-response relationship in GMT, with the 
Group 8 40 µg CHIKV VLP + 300 µg alum adjuvant single dose resulting in 86% 
seroresponse (titers ≥40) 7 days postvaccination as well as the highest GMTs at Day 182. 
Seroresponse was well maintained at 760 days in Group 8 participants (16).  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 28 of 80 
1.3.3 Seroresponse Rate 
In historical studies, a human SNA assay threshold titer of  ≥40 was used, however after 
discussions with regulatory agencies, anti-CHIKV SNA titer 
 (seroresponse rate, also 
considered the presumptive seroprotection rate) will be used in the present and future studies. 
1.3.4 Rationale for Dosage and Route of Administration 
The regimen of PXVX0317 selected for this study is 40 µg of CHIKV VLP with alum 
adjuvant administered in a single IM dose on Day 1. The alum dose of 300 µg is within the 
range of doses of alum adjuvants used in many licensed vaccines, including VLP-based 
vaccines. This dose also creates a concentration ratio to PXVX0317 that achieves high 
(~90%) levels of adsorption, thought to enhance both immunogenicity and short-term 
stability. The IM route of administration is consistent with that in previous clinical studies 
(VRC 311 (12, 13), VRC 704 (14, 15), PXVX-CV-317-001 (16), and EBSI-CV-317-002). 
This regimen was selected by an interim analysis of the PXVX-CV-317-001 study data. All 
regimens tested were given to groups of 50 to 53 healthy adults and all resulted in 100% 
seroconversion by Day 57. The group receiving a single dose of 40 µg plus alum showed the 
highest anti-CHIKV SNA GMT at Day 182 and Day 365.  
The PXVX0317 vaccine (40 µg CHIKV VLP + 300 µg alum adjuvant) single dose was 
selected for further development by the sponsor in this phase 3 clinical study 
(EBSI-CV-317-004). 
1.4 
Justification for Inclusion of Adolescents 12 to <18 Years of Age 
This study will enroll adolescents 12 to <18 years of age. The accumulated evidence to date 
supports the safety and immunogenicity of PXVX0317 and inclusion of adolescents in this 
study. To date, 713 adults have received at least one dose of the vaccine candidate 
(PXVX0317 or VRC-CHKVLP059-00-VP). No vaccine-related SAEs or deaths have 
occurred. No significant imbalances in unsolicited AEs have been observed that raise 
concern for a safety signal associated with immunization. Based on results from completed 
phase 1 and 2 studies (VRC 311 (12, 13), VRC 704 (14, 15)), and the phase 2 clinical study 
(PXVX-CV-317-001) (16), PXVX0317 vaccine is expected to induce robust SNA titers 
postvaccination. The 40 µg single, adjuvanted dose resulting in 96% seroresponse (human 
SNA assay titers ≥40) at Day 365 and SNA GMT of 1712 at Day 57 and 466 at Day 365. 
Data from the completed double-blind, randomized, placebo-controlled, multi-center phase 2 
study (VRC 704) conducted with an unadjuvanted formulation (two doses of 20 µg on Days 
0 and 28) in 400 healthy adults living in a CHIKV-endemic area (Caribbean) indicated that 
the product elicited neutralizing antibodies in 99.5% of vaccine recipients and that the 
neutralizing antibody response persisted for at least 18 months (14, 15). 
The US adolescents enrolled in this study have the prospect to directly benefit from 
vaccination against CHIKV following exposure to CHIKV due to: i) travel to CHIKV-

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 29 of 80 
endemic areas or areas where CHIKV epidemics are actively occurring; ii) local 
autochthonous transmission in the US and; iii) the occurrence of a CHIKV epidemic in the 
US. Although CHIKV has been known to cause periodic epidemics in tropical regions, in 
2013 CHIKV was identified in the Western Hemisphere in the Caribbean (19). With the 
global expansion of CHIKV and the frequency of travel, the potential for exposure to 
CHIKV has increased. Local transmission of CHIKV has been reported in approximately 117 
countries or territories worldwide, including the US (20). Each year, millions of travelers 
visit countries where CHIKV outbreaks are ongoing (21, 22). In 2014 alone, 2799 cases of 
CHIKV disease occurred in US travelers returning from affected areas (22). From 2014 to 
2017, approximately 10% of 3941 travel-acquired CHIKV cases were in individuals under 20 
years of age (7.5% were 10 to 19 years of age and 2% were <10 years of age). Of those 10 to 
19 years of age, just under 20% were hospitalized as a result of their illness (23). Locally 
transmitted cases have been reported in the US since 2013 (22).  
With expanded distribution of the Ae. aegypti and Ae. albopictus mosquito-vectors in the US 
and the increase in travel, epidemiologic models indicate that the US remains susceptible to 
epidemics (24). Although locally transmitted cases are currently reported to occur in small 
numbers, as more CHIKV-infected travelers come into the US, the likelihood that local 
CHIKV transmission could occur is increased (25).   
CHIKV epidemics, when they occur, are characterized by decades of inactivity interspersed 
with sudden outbreaks. The available methods to accurately predict when emerging CHIKV 
epidemics will occur are limited (26). In this regard, susceptible adolescents living in the US 
and susceptible adolescents living in an area where a CHIKV epidemic has occurred in the 
past share a similar prospect for direct benefit of vaccination. 
2 
STUDY OBJECTIVES AND PURPOSE 
2.1 
Purpose 
The purpose of this phase 3, randomized, double-blind, placebo-controlled study is to 
evaluate the safety and immunogenicity to PXVX0317 in adult and adolescent participants 
12 to <65 years of age. 
2.2 
Coprimary Objectives 
•
To evaluate the safety of PXVX0317 in healthy adult and adolescent participants 12
to <65 years of age.
•
To compare the anti-CHIKV SNA response to PXVX0317 and placebo at Day 22, as
measured by GMT and clinically relevant difference in seroresponse rate (PXVX0317
minus placebo).

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 30 of 80 
Note: Seroresponse rate (considered the presumptive seroprotection rate) is defined as 
the percentage of participants who achieve an anti-CHIKV SNA titer 
 See Section 
6.1 for assay description. 
•
To demonstrate the consistency of the anti-CHIKV SNA response across three
consecutively manufactured lots of PXVX0317 at Day 22 as measured by GMT.
2.3 
Secondary Objectives
•
To compare the anti-CHIKV SNA response to PXVX0317 and placebo at Day 15,
Day 183, and Day 8, as measured by GMT and seroresponse rate.
•
To compare the anti-CHIKV SNA response to PXVX0317 and placebo in
participants 12 to <18 years of age, participants 18 to <46 years of age, and
participants 46 to <65 years of age as measured by GMT and seroresponse rate.
2.4 
Exploratory Objective
•
To evaluate anti-CHIKV SNA response across three consecutively manufactured lots
of PXVX0317 as measured by seroresponse rate for each lot at Day 22 in participants
18 to <46 years of age.
3 
STUDY DESIGN 
3.1 
Study Description 
This is a phase 3 randomized, placebo-controlled, double-blind, parallel-group design with 
four treatment groups. Participants will be randomized in a 2:2:2:1 ratio within each of the 
three age strata (ages 12 to <18, 18 to <46, and 46 to <65) to receive one of three 
consecutively manufactured lots of PXVX0317 or placebo. With 3150 participants enrolled, 
the treatment group totals are estimated as follows: 
•
Group 1- PXVX0317 lot A: n=900
•
Group 2- PXVX0317 lot B: n=900
•
Group 3- PXVX0317 lot C: n=900
•
Group 4- Placebo: n=450
A nested lot consistency sub study will be performed in adult participants 18 to <46 years of 
age in the PXVX0317 treatment groups (lot A, lot B, and lot C).  
3.1.1 Study Centers 
This multicenter study will be conducted in the US, using up to 50 sites. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 31 of 80 
3.1.2 Number of Participants (Planned) 
At least 3150 enrolled healthy US adolescent and adult participants ages 12 to <65, stratified 
in three age groups: 12 to <18, 18 to <46, and 46 to <65 years of age. Enrollment will target 
at least 245 participants (210 PXVX0317 participants and 35 placebo participants) into the 
youngest and oldest age groups (12 to <18 and 46 to <65 years of age, respectively). The 
middle age group must include at least 1050 participants to provide adequate power for the 
lot consistency analysis. 
3.1.3 Estimated Study Duration 
The per participant estimated total study duration is 212 days. The screening window will be 
no greater than 30 days prior to Day 1 (randomization and administration of IP). The immune 
response to PXVX0317 will be measured by anti-CHIKV SNA up to Day 183 End of Study 
Visit.   

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 32 of 80 
3.2 
Schematic Diagram of Study Design 
Figure 2 
EBSI-CV-317-004 Schematic Diagram of Study Design 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 33 of 80 
3.3 
Description of Study Assessments 
The underlying subsections (Section 3.3.1 through Section 3.3.12) describe the planned study 
procedures and assessments. For the per visit timing of these procedures and assessments 
refer to Section 5.2 and the study Schedule of Events. Information on participant consent 
(and assent, as applicable) is described in Section 11.1. 
3.3.1 Review of Eligibility Criteria 
Review of inclusion and exclusion criteria should be completed, and participant eligibility 
confirmed prior to planned vaccination. Refer to Section 4.1 and Section 4.2 for criteria. 
3.3.2 Medical History and Demography 
Medical history information will be collected from participants at the Screening Visit and 
confirmed at the Day 1 Visit (at baseline ie, prior to IP administration) and will include (but 
not be limited to) demographic information (date of birth, race, ethnicity, and sex of 
participant), current and past medical conditions (including presence of joint pain), prior and 
concomitant medications (see Section 5.3) taken within 30 days of Screening Visit (or within 
90 days, for blood products). 
3.3.3 Physical Examination 
A complete physical examination will be performed on participants during the Screening 
Visit. The examination should include general appearance, eyes-ears-nose-throat, head-neck, 
lungs-chest, heart, abdomen, musculoskeletal, lymph nodes, skin, extremities, and 
neurological assessment.  
A targeted physical examination may be performed on participants at additional time points 
if indicated by AE, MAAE, SAE, or AESI reports. 
3.3.4 Vital Signs 
Vital signs collected after 5 minutes of rest and prior to blood work without distractions from 
participants will include blood pressure, heart rate, respiratory rate, and temperature. The first 
set of screening vitals are to be collected and transcribed into the screening electronic case 
report form (eCRF) for inclusion of the participant into the study. Repeat measurements on 
abnormal vital parameters are allowed twice for confirmation of eligibility to receive the 
vaccination.  
Measurement of body weight and height for BMI calculations will be obtained at the 
Screening Visit. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 34 of 80 
3.3.5 Laboratory Tests 
At the Screening Visit, blood samples will be collected for serum testing for Hepatitis B 
surface antigen (HBsAg), HCV antibody (if HCV antibody is positive HCV RNA testing can 
be performed), HIV-1/HIV-2, serum pregnancy test for women of CBP, and for FSH testing 
for postmenopausal women (for additional information on FSH assessment see Section 
3.3.7). Urine toxicology screening may be done per investigator’s (or designee’s) discretion 
at the Screening Visit. Any request to repeat testing should be discussed with the MM. 
For additional information on sample collection, processing, storage, and shipment refer to 
the study Laboratory Manual.  
3.3.6 Immunogenicity Sample 
Anti-CHIKV SNA titers will be assessed using a validated human SNA assay that measures 
neutralization titer of 80% (NT80). Blood (serum) samples will be taken on Day 1 (prior to IP 
administration), Day 8, Day 15, Day 22, and the Day 183 End of Study Visit (or at Early 
Discontinuation/Withdrawal). For information on the immunogenicity assessment see 
Section 6.1.  
For additional information on sample collection, processing, storage, and shipment refer to 
the study Laboratory Manual. 
3.3.7 Pregnancy Testing and Contraception 
Women of CBP will undergo a serum pregnancy test at the Screening Visit, and a urine 
pregnancy test prior to IP administration on Day 1. The participant must have a negative 
urine pregnancy test on Day 1, prior to administration of IP.  
Women of CBP must also use an acceptable method of contraception from prior to Day 1 
through Day 183 End of Study Visit. Acceptable methods include highly effective forms of 
contraception: hormonal contraceptives (eg, implants, pills, patches) containing combined 
estrogen and progestogen, or progestogen-only initiated ≥30 days prior to dosing or IUD 
inserted ≥30 days prior to dosing or use of double barrier type of birth control (male condom 
with female diaphragm, male condom with cervical cap). Abstinence is acceptable only for 
adolescents (12 to <18 years of age) who are not sexually active. 
Note: Contraception requirements do not apply for participants in exclusively same-sex 
relationships and these participants should have no plans to become pregnant by any other 
means for the duration of the study. 
The investigator must confirm that contraception methods (eg, hormonal contraceptive or 
intrauterine device) were initiated ≥30 days prior to Day 1 to be considered fully effective. 
For female participants who are postmenopausal, documented FSH level of ≥40 mIU/mL 
must be obtained. If the FSH is <40 mIU/mL, the participant must agree to use an acceptable 
form of contraception (see above).  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 35 of 80 
The investigator must report any pregnancies as described in Section 7.3.1. 
3.3.8 Investigational Product Administration 
Investigational product single dose is 0.8 mL in volume and administered by IM injection 
into the deltoid with a pre-filled syringe attached to 25 gauge 1” (or 1.5”) needle, using 
universal precautions and sterile technique in accordance with General Best Practice 
Guidelines for Immunization: Best Practices Guidance of the Advisory Committee on 
Immunization Practices (ACIP) (27) per Table 1. Injections will be administered by a staff 
member delegated by the investigator. 
Table 1 
Needle Length of Intramuscular Injections for Children (by Age) and Adults Aged ≥19 
Years (By Sex and Weight) 
Sex, Weight 
Needle length 
Injection Site 
Men and women, <60 kg (<130 lbs) 
1 inch (25 mm) 
Deltoid muscle of arm 
Men and women, 60-70 kg (130-152 lbs) 
1 inch (25 mm) 
Men, 70-118 kg (152-260 lbs) 
1-1.5 inches (25-38 mm)
Women, 70-90 kg (152-200 lbs) 
Men, >118 kg (260 lbs) 
1.5 inches (38 mm) 
Women, >90 kg (200 lbs) 
Children, 12 to <18 years of age 
5/81-1 inch (16-25 mm) 
Source: Adapted from Table 6-2, General Best Practice Guidelines for Immunization: Best Practices 
Guidance of the Advisory Committee on Immunization Practices (ACIP) (27).  
1If skin is stretched tightly and subcutaneous tissues are not bunched. 
Investigational product is to be administered only under the direct supervision of the 
investigator or a qualified subinvestigator identified on the FDA Form 1572. Under no 
circumstances will the investigator allow PXVX0317 vaccine to be used other than as 
specified in the protocol. 
For further details on the IP refer to Section 5.1. 
3.3.9 Acute Observation After Investigational Product Administration 
The participant will be monitored by study staff for signs of an acute adverse reaction for 30 
min after injection. Vital signs will be obtained 30 min to 1 hr after injection. 
3.3.10 Solicited Adverse Events 
Solicited AEs will be collected from IP administration until Day 8. Solicited AEs for this 
study are local events of pain, redness, and swelling at the injection site and systemic events 
of oral temperature ≥38.0°C (≥100.4°F), chills, fatigue, headache, myalgia, arthralgia, and 
nausea (Section 7.1.2 and Section 7.1.2.1).  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 36 of 80 
Participants will be trained to complete an e-diary to observe, measure, and record these 
solicited AEs. In the occurrence of issues with the e-diary, a paper diary (subject memory 
aid) may be implemented as a back up. To measure oral temperature, a digital thermometer 
will be provided to the participant to measure their temperature each day and record them in 
their e-diary. To record injection site local reactions, a ruler will be provided to the 
participant to measure and record the diameter of redness and swelling at the largest point of 
the reaction each day. Adolescent participants will be instructed to complete the e-diary. 
Parents/guardians may provide assistance to adolescents to measure and record temperature 
and injection site reactions. 
Study staff will review the signs and symptoms recorded in the e-diary. The investigator will 
then assess all solicited AEs for severity (Section 7.1.7) and the action taken, and causality 
(Section 7.1.8). The results of the investigator’s assessment will be recorded as a separate 
source document and will be entered on the solicited AE eCRF. Symptoms continuing 
beyond the solicited AE collection period will be collected and recorded on the AE eCRF.  
Details on definition, evaluation, reporting periods and documentation are outlined in Section 
7. 
3.3.11 Unsolicited Adverse Events 
Unsolicited AEs (AEs not listed in the e-diary) will be collected from Day 1 through 28 days 
postvaccination (Day 29) (Section 7.1.3). 
Details on definition, evaluation, reporting periods and documentation are outlined in Section 
7. 
3.3.12 Serious Adverse Events and Adverse Events of Special Interest 
Serious adverse events, AESI, and MAAEs will be collected for all participants from Day 1 
through Day 183 End of Study Visit (Section 7.1.4 and Section 7.1.5). 
Details on definition, evaluation, reporting periods and documentation are outlined in Section 
7. 
3.4 
Measures Taken to Minimize/Avoid Bias 
3.4.1 Treatment Assignment/Randomization 
Participant eligibility will be confirmed and documented by the investigator immediately 
prior to randomization of each participant. Study staff will indicate on a randomization eCRF 
within the electronic data capture (EDC) system that they want to generate a randomization 
number for the participant. When they agree to proceed, a randomization number will be 
generated from the EDC randomization module but hidden from study staff. The EDC 
randomization module will match the randomization number to an IP kit available at the site 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 37 of 80 
and inform the study staff of the assigned kit. Study staff will use the appropriate kit for 
administration to the participant.   
Participants will be considered enrolled once a randomization number has been assigned 
within the EDC system. The study will be conducted as a double-blind study through Day 
183 End of Study Visit. Neither participants, nor clinical site personnel, including the 
investigators, nor the sponsor will know participants' individual treatment assignments until 
all participants have completed their participation in the study through the Day 183 End of 
Study Visit and the database has been cleaned and locked. 
3.4.2 Masking/Blinding Procedures 
Study participants, the investigator, and study site personnel will remain blinded to all 
randomization assignments throughout the study. The sponsor’s MM and personnel, who are 
in regular contact with the study site and/or involved with documentation associated with the 
study will remain blinded to all participant randomization assignments. 
The following safeguards will be employed to reduce the risk of inadvertent unblinding: 
•
Use of a standardized pre-filled syringe and injection volume for all injections.
•
All PXVX0317 and placebo syringes have a semitransparent barrel cover to mask any
difference in appearance between placebo and PXVX0317.
•
No sponsor personnel will have access to the randomization schedule. No site
personnel will have access to treatment assignments. The Randomization and Trial
Supply Management (RTSM) system allows for unblinding in an emergency (see
Section 7.7).
•
Assays will be run in a blinded manner. The assay titer results will not be delivered to
the sponsor data management and analysis team until after database lock, as they are
potentially unblinding.
•
Should any participant or staff member become inadvertently unblinded, the
investigator will promptly (within 24 hours of their awareness of the error) disclose
the event to the sponsor’s MM in a blinded fashion (disclosing only participant
number, not treatment) so that corrective action can be initiated. The unblinding
sequence of events will be documented and retained as source documents. A protocol
deviation will be entered in the eCRF.
3.5 
End of Study 
An individual participant is considered to have completed study participation after 
completion of the Day 183 (-14/+7) Visit 8 and any required safety follow-up.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 38 of 80 
4 
SELECTION AND WITHDRAWAL OF PARTICIPANTS 
4.1 
Inclusion Criteria 
Participants must meet all the following criteria to be enrolled: 
1.
Able and willing to provide informed consent (and assent, as applicable) voluntarily
signed by participant (and guardian, as applicable).
2.
Males or females, 12 to <65 years of age.
3.
Generally healthy, in the opinion of the investigator, based on medical history, physical
examination, and screening laboratory assessments.
4.
Women who are either:
i.
Not of CBP: pre-menarche, surgically sterile (at least six weeks post bilateral
tubal ligation, bilateral oophorectomy, or hysterectomy), or postmenopausal
(defined as a history of ≥12 consecutive months without menses prior to
randomization in the absence of other pathologic or physiologic causes, following
cessation of exogenous sex-hormonal treatment).
or: 
ii.
Meeting all the below criteria:
•
Negative serum pregnancy test at Screening Visit
•
Negative urine pregnancy test immediately prior to dosing at Day 1
•
Use one of these acceptable methods of contraception (if women of CBP) for
the duration of participation:
•
Hormonal contraceptives (eg, implants, pills, patches) initiated ≥30 days
prior to dosing
•
Intrauterine device inserted ≥30 days prior to dosing
•
Double barrier type of birth control (male condom with female diaphragm,
male condom with cervical cap)
•
Abstinence is acceptable only for adolescents (12 to <18 years old) who
are not sexually active.
Note: See Section 3.3.7 for this study’s list of acceptable method of contraception. 
Note: Contraception requirements do not apply for participants in exclusively same-sex 
relationships and these participants should have no plans to become pregnant by any other 
means for the duration of the study. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 39 of 80 
4.2 
Exclusion Criteria 
Participants who meet any of the following criteria cannot be enrolled: 
1.
Currently pregnant, breastfeeding, or planning to become pregnant during the study.
2.
Body mass index ≥35 kg/m2.
3.
Positive laboratory evidence of current infection with HIV-1/HIV-2, HCV, or HBV.
4.
History of severe allergic reaction or anaphylaxis to any component of the IP.
5.
History of any known congenital or acquired immunodeficiency that could impact
response to vaccination (eg, leukemia, lymphoma, generalized malignancy, functional or
anatomic asplenia, alcoholic cirrhosis).
6.
Prior receipt or anticipated use of systemic immunomodulatory or immunosuppressive
medications from six months prior to screening through Day 22. Note: For systemic
corticosteroid use at a dose or equivalent dose of 20 mg of prednisone daily for 14 days
or more within three months of screening through Day 22 is exclusionary. The use of
inhaled, intranasal, topical, ocular, or intraocular steroids is allowed.
7.
Receipt or anticipated receipt of blood or blood-derived products from 90 days prior to
screening through Day 22.
8.
Acute disease within the last 14 days (participants with an acute mild febrile illness can
be considered for a deferral of vaccination two weeks after the illness has resolved and
treatment has been completed).
9.
Clinically significant cardiac, pulmonary, rheumatologic, or other chronic disease, in the
opinion of the investigator. This may include chronic illness requiring hospitalization in
the last 30 days prior to screening.
10.
Enrollment in an interventional study and/or receipt of another investigational product
from 30 days prior to screening through the duration of study participation.
11.
Receipt or anticipated receipt of any vaccine from 30 days prior to Day 1 through Day
22.
12.
Evidence of substance abuse that, in the opinion of the investigator, could adversely
impact the participant’s participation or the conduct of the study.
13.
Prior receipt of an investigational CHIKV vaccine/product.
14.
Any other medical condition that, in the opinion of the investigator, could adversely
impact the participant’s participation or the conduct of the study.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 40 of 80 
4.3 
Withdrawal of Participants 
4.3.1 Participant Consent Withdrawal 
All participants can withdraw from participation in this study at any time, for any reason, 
specified or unspecified, and without penalty. The investigator will ask (but cannot require) 
such participants to provide the reason(s) for withdrawal of consent and to undergo an Early 
Withdrawal Visit. An individual is considered to undergo early withdrawal if they stop study 
participation before Day 183 End of Study Visit. 
Safety follow-up for AEs should occur for all participants. For information on safety 
follow-up for withdrawn participants see Section 4.3.3.  
4.3.2 Investigator-Based Participant Withdrawal 
The Investigator may withdraw a participant from further participation in the study, at their 
discretion, if medically necessary or for reasons of noncompliance. The reason for 
withdrawal of any participant must be clearly documented on the study source documents 
and the appropriate eCRF. The investigator is encouraged to consult the sponsor prior to the 
withdrawal of any participant, except in the event of a medical emergency.  
The investigator (and/or sponsor) may withdraw a participant from the study for any of, but 
not limited to, the following reasons: 
•
Noncompliance with the protocol. If the participant is noncompliant with protocol
requirements, the issue should be discussed with the participant and, if not resolved,
consideration given to withdrawing the participant.
•
Lost to follow-up; requires documentation of at least three unsuccessful attempts to
contact participants. Lost to follow-up will be determined after the date of the
participant’s projected last visit.
•
Other reason(s) which, in the opinion of the investigator, indicates that continued
participation in the study is not in the best interest of the participant.
Safety follow-up for AEs should occur for all participants. For information on safety follow-
up for withdrawn participants see Section 4.3.3.  
4.3.3 Follow-up for Withdrawn Participants 
Outreach will be made to ensure that participants who are withdrawn, or who withdraw from 
the study, during the active observation or follow-up period will complete all safety and 
available assessments for the Early Withdrawal Visit as outlined in this protocol. The 
investigator should inform the participant that these assessments are for their own well-being 
and, if possible, for study purposes. Additional information regarding ongoing AEs may be 
provided as a follow-up report.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 41 of 80 
4.3.4 Documentation of Withdrawal/Discontinuation 
Reasons for withdrawal of individual participants from the study prior to final protocol 
required visit and/or final safety follow-up are to be recorded on the eCRF. The reason for 
withdrawal from the study will be recorded as one of the following: 
•
Lost to Follow-up (Note: Requires documentation of at least three unsuccessful
attempts to contact participants, lost to follow-up will be determined after the date of
the participant’s projected last visit)
•
Adverse event
•
Pregnancy
•
Protocol deviation (that results in discontinuation)
•
Noncompliance to IP
•
Physician (ie, investigator) decision
•
Other
Safety follow-up for AEs should occur for all participants, for information on safety follow-
up for withdrawn participants see Section 4.3.3. 
4.3.5 Participant Replacement  
Participants who undergo Early Discontinuation or withdrawal of consent after 
randomization and before receiving treatment may be replaced at the sponsor’s discretion. 
Participants who undergo Early Discontinuation after vaccination will not be replaced.   
5 
TREATMENT OF PARTICIPANTS 
5.1 
Investigational Products 
5.1.1 PXVX0317 Vaccine 
The PXVX0317 vaccine is comprised of CHIKV VLP adsorbed on aluminum hydroxide 
adjuvant 2%, and formulation buffer supplied as a single dose in a pre-filled glass syringe. 
CHIKV VLP refers to the VLP component of PXVX0317 produced by transient transfection 
of human embryonic kidney (HEK293) cells with a deoxyribonucleic acid expression 
plasmid encoding capsid (C) and envelope (E) E3, E2, 6K, and E1 proteins. After expression 
of the plasmid-encoded proteins, VLPs self-assemble and are released into the cell culture 
medium as ~70 nm particles. The 6K and E3 proteins have not been specifically detected in 
the VLPs. No replication-capable viral genetic material is incorporated into the VLPs. Virus-
like particles are then concentrated from the cell supernatant purified, and buffer exchanged. 
The VLPs are then formulated with excipients and aluminum hydroxide adjuvant, mixed, and 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 42 of 80 
filled into 1 mL glass syringes with a 0.8 mL deliverable volume. The glass syringe is sealed 
with a rubber closure and plastic cap. The rubber closure does not contain natural latex.  
Placebo (formulation buffer) is supplied as a single dose of 0.8 mL in a pre-filled syringe. 
See the pharmacy manual and the IB for additional information, including composition of 
PXVX0317 vaccine. 
5.1.2 Placebo Pre-filled Syringe 
The placebo is a sterile aqueous solution with the same excipient composition as the drug 
product without CHIKV VLP and aluminum hydroxide adjuvant. The placebo is filled into 1 
mL glass syringes with a 0.8 mL deliverable volume. The placebo is stored at 2.0 to 8.0°C. 
The glass syringe is sealed with a rubber closure and plastic cap. The rubber closure does not 
contain natural latex. 
See the pharmacy manual for additional information, including composition of the placebo. 
5.1.3 Labeling 
Investigational product (PXVX0317 vaccine and placebo) will be shipped in carton kits 
containing labelled pre-filled syringes. Kits and syringes will be labelled with the following 
information: 
•
“Caution: New Drug – Limited by Federal Law to Investigational Use Only”
•
Investigational product name – PXVX0317 vaccine or placebo (to maintain the blind
both names will be included)
•
Dose volume and container – single dose of 0.8 mL in a pre-filled syringe
•
Route of administration – Intramuscular
•
Randomization kit number (in lieu of lot numbers and manufacture date and/or expiry
date to maintain the blind)
•
Protocol number – EBSI-CV-317-004
•
Recommended storage temperature/conditions – stored refrigerated at 2.0 to 8.0°C
•
Sponsor – Emergent Travel Health Inc.
5.1.4 Investigational Product Shipment 
Investigational product will be shipped to the site at a temperature of 2.0 to 8.0°C. During 
shipment, the temperature of the IP will be monitored to ensure the required temperature 
conditions are maintained. The principal investigator (or designee) will be responsible for 
checking the number of syringes and the condition of the syringes received, and entering this 
information into the drug accountability records, and reporting the condition of shipment to 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 43 of 80 
the sponsor and drug depot. Investigational product received in good condition will be 
automatically released for use upon confirmation of receipt as such within the RTSM system; 
shipments received with any excursions/issues will be placed under quarantine by the site 
and released for use by the sponsor following investigation. For additional information on IP 
shipments please refer to the study pharmacy manual.     
5.1.5 Storage Conditions 
Investigational product (PXVX0317 vaccine and placebo) must be stored refrigerated at 2.0 
to 8.0°C in a secured area until used. The temperature in the storage area must be monitored 
with properly calibrated instruments and recorded on a temperature log. Any excursions must 
be promptly reported to the sponsor via the RTSM system; product should be quarantined by 
the site and may be released for use by the sponsor only after investigation and confirmation 
of continued stability. Please refer to the pharmacy manual for additional details.  
5.1.6 Preparation 
Investigational product (PXVX0317 vaccine and placebo) will be supplied as a single dose of 
0.8 mL in a pre-filled syringe shipped in kits. See Section 3.3.8 for more details. 
5.1.7 Drug Accountability 
The investigator is responsible for maintaining accurate inventory records of IP. The 
investigator (or designee) will inventory all IP shipments upon receipt. The investigator must 
ensure that all drug supplies are kept in a secure location in the site pharmacy in accordance 
with recommended storage conditions (Section 5.1.5). Inventory and ongoing record of test 
material supplies will be documented using the electronic drug accountability form provided 
within the clinical trial material tracking module of the sponsor’s RTSM system. These 
records will be reviewed by representatives of the sponsor and may be reviewed by 
regulatory agencies.  
5.2 
Study Procedures and Assessments by Visit 
The timing of the study procedures and assessment below are shown in the Schedule of 
Events and a description of each procedure and assessment is described in Section 3.3.  
5.2.1 Screening (Visit 1, within 30 days of Day 1) 
Eligible participants will first undergo informed consent counseling. Once informed consent 
has been obtained, participants will undergo a Screening Visit to ascertain their eligibility in 
this study within 30 days prior to Day 1. The Screening Visit assessments will include: 
•
Informed consent (and informed assent, as applicable) (Section 11.1).
•
Review of eligibility criteria (Section 3.3.1, Section 4.1, Section 4.2).

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 44 of 80 
•
Medical history (including presence of joint pain) (Section 3.3.2).
•
Demographics (date of birth, race, ethnicity, and sex of participant) (Section 3.3.2).
•
Prior and current medications (Section 3.3.2, Section 5.3).
•
Vital signs (blood pressure, heart rate, respiratory rate, and temperature) as well as
height and body weight (for BMI calculation) (Section 3.3.4).
•
Complete physical exam (general appearance, eyes-ears-nose-throat, head-neck,
lungs-chest, heart, abdomen, musculoskeletal, lymph nodes, skin, extremities, and
neurological assessment) (Section 3.3.3).
•
Blood collection for laboratory viral marker testing (HBsAg, HCV antibody [if HCV
antibody is positive, HCV RNA testing can be performed], HIV-1/HIV-2) (Section
3.3.5).
•
For women of CBP: blood sample for serum pregnancy test (Section 3.3.5, Section
3.3.7).
•
For postmenopausal women: blood sample for FSH levels (Section 3.3.5, Section
3.3.7).
•
Urine sample for toxicology (per investigator’s [or designee] discretion) (Section
3.3.5).
5.2.1.1 
Rescreening 
Rescreening may occur given the following circumstances: 
•
If the participant has an acute febrile illness at the time of their scheduled enrollment,
they may be re-screened 14 days after resolution of their acute illness.
•
If the participant is asymptomatic but tests positive by reverse transcription
polymerase chain reaction (RT-PCR) for severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2) they may be rescreened provided 14 days have elapsed
since the participant tested RT-PCR positive for SARS-CoV-2, the participant
continues to be asymptomatic, and the participant is otherwise eligible for enrollment.
•
Participants who have received licensed vaccines within 30 days of anticipated Day 1
may be rescreened provided no additional doses are anticipated up to Day 22.
•
Participants who have received blood products or investigational products from
participation in another clinical study may be rescreened after the appropriate
duration has passed (90 days for blood products; 30 days for investigational drugs; six
months prior to Screening Visit for systemic immunomodulatory or
immunosuppressive medications).
•
Eligible participants who are not able to be vaccinated with IP within 30 days of their
screening period may be rescreened.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 45 of 80 
Rescreened participants must undergo all screening procedures again, including reconsenting 
and use of the same participant ID number. Participants may be rescreened one time only. 
Rescreening is not otherwise permitted. 
5.2.2 Day 1 (Baseline, Randomization, and Administration of IP) Visit 2 
The following will take place during the visit and prior to IP administration: 
•
Reverification of eligibility criteria.
•
Review medical history.
•
Review prior and concomitant medications.
•
Vital signs.
•
Directed physical exam (as needed, if indicated by medical history).
•
For women of CBP: urine pregnancy test.
•
Blood collection for anti-CHIKV SNA (Section 3.3.6, Section 6.1).
•
Randomization (Section 3.4.1).
•
IP administration (Section 3.3.8, Section 5.1).
The following will take place during the visit and after IP administration: 
•
In-clinic acute observation (Section 3.3.9).
•
Vital signs.
•
E-diary device, digital thermometer, and ruler distribution, set-up, and training
(Section 3.3.10).
•
Solicited AE, unsolicited AE, MAAE, SAE, and AESI (Sections 3.3.10 - 3.3.12,
Section 7) evaluation.
•
Record any medications that were given to participants after IP administration.
5.2.3 Day 8 (-1/+3) Visit 3 
•
Review e-diary.
•
Solicited AE, unsolicited AE, MAAE, SAE, and AESI evaluation.
•
Review concomitant medications.
•
Blood collection for anti-CHIKV SNA.
•
Directed physical exam (as needed).

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 46 of 80 
5.2.4 Day 15 (-1/+3) Visit 4 
•
Unsolicited AE, MAAE, SAE, and AESI evaluation.
•
Review concomitant medications.
•
Blood collection for anti-CHIKV SNA.
•
Directed physical exam (as needed).
5.2.5 Day 22 (-1/+3) Visit 5 
•
Unsolicited AE, MAAE, SAE, and AESI evaluation.
•
Review concomitant medications.
•
Blood collection for anti-CHIKV SNA.
•
Directed physical exam (as needed).
5.2.6 Day 29 (±1) Telephone Contact for Visit 6 
•
Unsolicited AE, MAAE, SAE, and AESI evaluation.
•
Review concomitant medications.
5.2.7 Day 92 (±3) Telephone Contact for Visit 7 
•
SAE, AESI, and MAAE evaluation.
•
Review concomitant medications (only if associated with SAE/AESI/MAAE).
5.2.8 Day 183 (-14/+7) Visit 8 End of Study 
•
SAE, AESI, and MAAE evaluation.
•
Review concomitant medications (only if associated with SAE/AESI/MAAE).
•
Directed physical exam (as needed).
•
Blood collection for anti-CHIKV SNA.
5.2.9 Early Discontinuation/Withdrawal Visit 
If the Early Discontinuation/Withdrawal Visit occurs: i) within 7 days after IP 
administration, the Visit 3 schedule will be followed; ii) from 7 days through 21 days after IP 
administration, the Visit 5 schedule will be followed and; iii) after Day 22, the Visit 8 
schedule will be followed.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 47 of 80 
5.2.10 Unscheduled Visits 
Any study procedure, excluding vaccination, may be conducted at an Unscheduled Visit as 
needed and recorded on the Unscheduled Visit eCRF. Examples include repeat specimen 
collection and additional safety follow-up for an SAE/AESI/MAAE/AE.  
5.3 
Prior and Concomitant Medications 
At the Screening Visit, the details of prior and concomitant medication usage will be 
collected (through 30 days prior to screening, or 90 days for blood products, or six months 
prior to screening for systemic immunomodulatory or immunosuppressive medications). 
Concomitant medications will be collected at each on site visit or by phone interview (or 
early discontinuation/withdrawal) for all groups. The details of all concomitant medications 
including those associated with solicited AEs and unsolicited AEs will be collected. After 
Day 29 only concomitant medications associated with SAEs, AESI, and MAAEs will be 
collected through the end of the study. 
5.3.1 Required Concomitant Medications 
Not applicable.  
5.4 
Procedures for Monitoring Participant Compliance 
All participants will be administered the IP by study staff. Compliance with study protocol 
and procedures will be monitored on an ongoing basis by study staff.  
6 
IMMUNOGENICITY ASSESSMENT 
6.1 
Immunogenicity Analysis 
The immunogenicity analysis will be performed using a high-throughput in vitro infectivity 
assay developed by the sponsor for assessing titers of neutralizing antibodies against CHIKV 
in serum samples. The assay is based on using a modified version CHIKV that expresses 
luciferase (CHIKV-luc) and measures the reduction of luciferase activity in infected cultures 
of Vero cells following treatment of virus with test serum. Using the human SNA assay, 
antibody neutralization titers can be determined via characterization of reductions of 
luciferase activity in the presence of immune serum. The quantitation of reporter gene 
expression, a correlate of the level of virus infection of cells, is determined by detection of 
luciferase in assay wells using a micro-plate luminometer. The CHIKV neutralizing antibody 
titer 80 (NT80) is the reciprocal of the serum dilution that provides 80% protection of Vero 
cells from CHIKV-luc infection or an 80% reduction of luciferase activity compared to virus 
only control.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 48 of 80 
For the statistical analysis of the anti-CHIKV SNA titers results obtained from sample 
analysis refer to Section 8.6.   
7 
 SAFETY ASSESSMENTS AND REPORTING 
7.1 
Definitions 
7.1.1 Adverse Event 
An AE is any untoward medical occurrence in a patient or clinical investigation participant 
administered a pharmaceutical product and that does not necessarily have a causal 
relationship with this treatment. An AE can therefore be any unfavorable and unintended sign 
(including an abnormal laboratory finding), symptom, or disease temporally associated with 
the use of a medicinal (investigational) product, whether or not related to the medicinal 
(investigational) product. 
Notes: 
•
A diagnosis should be captured as an AE term and signs and symptoms should be
captured only in the absence of a unifying diagnosis. If a diagnosis is ultimately made, it
should replace the previous report based on signs and symptoms.
•
In the event that there are multiple diagnoses, then all diagnoses should be captured.
•
The worsening of an existing sign, symptom or disease is also considered to be an AE.
•
An abnormal laboratory finding deemed by the principal investigator (or designee) as not
clinically significant (NCS) will not be captured as an AE, but an abnormal laboratory
finding that worsens after dosing with the IP, from not clinically significant to clinically
significant (CS), is considered an AE.
•
Surgical procedures are not AEs. They are the action taken to treat a medical condition.
Interventions that were planned prior to study entry for medical conditions that started
prior to study entry but did not worsen during the clinical study are not reported as AEs.
•
Medically attended adverse events: medically attended visits include hospital, emergency
room, urgent care clinic, or other visits to or from medical personnel. Routine scheduled
study visits will not be considered medically attended visits.
7.1.2 Solicited Adverse Event 
A solicited AE is a protocol-specified AE about which the investigator (or designee) 
proactively asks the participants during a protocol-specified time period. A reactogenicity 
event may be considered as a solicited AE per discretion of the investigator (as described 
below in Section 7.1.2.1). 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 49 of 80 
7.1.2.1 
Reactogenicity 
Reactogenicity (solicited systemic and local injection site reactions) will be assessed by the 
participants using e-diary cards. Information will be solicited on the following injection site 
reactions: pain, redness, and swelling. In addition, information will be solicited for AEs, on 
the following systemic reactions: temperature increases (oral) ≥38.0°C (≥100.4°F), chills, 
fatigue, headache, myalgia, arthralgia, and nausea.   
If injection site or systemic reactions continue beyond seven days postvaccination, these will 
be recorded in the EDC as unsolicited AEs. For any type of reactogenicity persisting two 
weeks or more, the investigator (or designee) will evaluate the reaction at the next scheduled 
visit and/or determine based on the nature and severity if a more immediate unscheduled 
follow-up visit is required to fully assess the reaction.  
7.1.3 Unsolicited Adverse Event 
An unsolicited AE is an AE that is spontaneously reported by the participant or discovered 
by the investigator.  
7.1.4 Adverse Event of Special Interest 
Arthralgia will be included as an AESI. The occurrence of new onset or worsening arthralgia 
that is medically attended will be monitored throughout the study for all participants. 
Medically attended visits include hospital, emergency room, urgent care clinic, or other visits 
to or from medical personnel. Routine scheduled study visits will not be considered 
medically attended visits. 
7.1.5 Serious Adverse Event 
An SAE is any untoward medical occurrence that: results in death, is life threatening, 
requires inpatient hospitalization or prolongation of existing hospitalization, results in 
persistent or significant disability/incapacity or substantial disruption of the ability to conduct 
normal life functions, or is a congenital anomaly or birth defect.  
Important medical events which may not result in death, be life threatening, or require 
hospitalization may be considered an SAE when, based upon appropriate medical judgment, 
they may jeopardize the patient or participant and may require medical or surgical 
intervention to prevent one of the outcomes listed in this definition. 
Notes: 
•
Death is an outcome and not an event. The condition leading to death is the event. If no
other information regarding the cause of death is available, the event will be considered
“Unspecified Adverse Event”.
•
Overnight stay at hospital/clinic that occurs during a study for social reasons (eg,
transportation difficulties, respite care) is not considered to be a hospitalization event.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 50 of 80 
7.1.6 Suspected Unexpected Serious Adverse Reaction 
Suspected Unexpected Serious Adverse Reaction (SUSAR) is the term used to refer to an AE 
that occurs in a clinical study participant, which is assessed by the sponsor and or study 
investigator as being unexpected, serious, and as having a reasonable possibility of a causal 
relationship (Section 7.1.8) with the IP.   
7.1.7 Severity of Adverse Events 
The investigator will grade all adverse events for severity. Adverse events listed in the 
grading scale in Appendix I will be graded according to the criteria in the table. Adverse 
events not listed in the grading scale will be graded as follows: 
•
Mild (Grade 1): No interference with activity
•
Moderate (Grade 2): Some interference with activity
•
Severe (Grade 3): Significant; prevents daily activity
•
Potentially Life-Threatening (Grade 4): As determined by emergency room visit or
hospitalization.
For the study grading scale see Appendix I. 
7.1.8 Causality of Adverse Events 
The investigator is responsible for the assessment of the causality of an AE and sponsor’s 
MM will also assess SAE causality, independent of the investigator.    
The following guidelines are provided for this assessment: 
•
Unrelated: No relationship between the IP and the reported event.
•
Possibly related: The event follows a reasonable temporal sequence from the time of
administration of IP and/or follows a known response pattern to the IP but could also
have been produced by other factors.
•
Probably related: A reasonable temporal sequence of the event with administration
of IP exists and based on the known response to the IP, known or previously reported
adverse reactions to the IP or similar products, or in the investigator’s (or designee)
clinical judgment the association of the event with the IP seems likely.
If the relationship between the AE and the IP is determined to be “possible” or “probable”, 
the event will be considered to be “related” to the IP, otherwise it will be considered “not 
related” for reporting purposes. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 51 of 80 
7.2 
Eliciting Adverse Events 
Adverse events reported spontaneously by the participant in response to an open question 
from the principal investigator (or designee) or revealed by observation (eg, during physical 
exam) will be recorded by the principal investigator (or designee) on the AE eCRF. Study 
participants will be provided with a 24-hour telephone number to contact study personnel in 
case of an untoward reaction. 
7.3 
Reporting Requirements for Immediately Reportable Events 
7.3.1 Principal Investigator’s Reporting Requirements 
The following events must be reported within 24 hours of awareness by the principal 
investigator (or designee) to sponsor’s Global Pharmacovigilance Department (Global PV), 
through completion of the AE eCRF within the EDC system, and identifying the event as 
serious (SAE):  
•
Any SAE regardless of causal association with the IP.
•
Any AESI regardless of causal association with the IP.
•
Confirmed pregnancy of female participants.
Should the EDC system for reporting SAEs, AESI, and pregnancy be unavailable, the 
appropriate form(s) (listed below) will be completed and sent by email to the following 
address:  
Global Pharmacovigilance Department 
Emergent BioSolutions Inc. 
The paper reported SAEs, AESI, and pregnancy should be entered in EDC once the system is 
available. 
For SAE/AESI, the “Serious Adverse Event/Adverse Event of Special Interest Report Form” 
will be completed (abbreviated hereafter as “SAE/AESI Report Form”). The SAE/AESI 
Report Form is not the same as the AE eCRF. Supporting documentation that may be 
uploaded into the EDC to accompany the form(s) can include source documentation or 
medical records (eg, discharge summary for hospitalizations, lab reports) which support a 
diagnosis. Participant identifiers (eg, name, address, telephone number, social security 
number, medical record number, or hospital/laboratory number) must be redacted from the 
source documentation.  

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 52 of 80 
All SAEs that are unexpected (eg, adverse drug reactions) must be reported to the 
Institutional Review Board (IRB) by the investigator (or designee) as required by ICH GCP 
E6. 
If a participant becomes pregnant during a study, the sponsor will be notified. All 
pregnancies where conception occurred after first exposure to the IP through the End of 
Study visit are to be followed to outcome (eg, delivery, spontaneous/elective/therapeutic 
abortion), including after the study is completed and even if the participant is withdrawn 
from the study. If a pregnancy results in an abnormal outcome that the reporting health care 
professional considers might be due to the IP, then the guidelines for expedited reporting of 
SUSAR should be followed (see Section 7.3.2). 
Any pregnancy that occurs during study participation must be reported using the clinical 
study pregnancy forms (“Pregnancy Notification Form” and “Pregnancy Follow-up Form”). 
To ensure participant safety, each pregnancy must be reported to the sponsor within 24 hours 
of learning of its occurrence. The pregnancy must be followed up to determine outcome 
(including premature termination) and status of mother and child. Pregnancy complications 
and elective terminations for medical reasons must be reported as an AE or SAE. 
Spontaneous abortions must be reported as an SAE. 
Any SAE occurring in association with a pregnancy brought to the investigator’s attention 
during or after the participant has completed the study and considered by the investigator as 
possibly related to the study treatment, must be promptly reported to the sponsor. 
The investigator is responsible to notify their IRB according to their policy. 
7.3.2 Sponsor’s Reporting Requirements 
A SUSAR is a suspected adverse reaction that is both serious and unexpected (Section 7.1.6). 
As specified in 21 Code of Federal Regulations (CFR) 312.32, SUSARs will be reported by 
the sponsor of the Investigational New Drug Application (IND) to the FDA and to all 
participating principal investigators in an IND safety report as soon as possible, no later than 
15 calendar days after the sponsor becomes aware of the suspected adverse reaction (21 CFR 
312.32(c)(1)).  
In addition, any unexpected fatal or life-threatening suspected adverse reaction will be 
reported to FDA no later than seven calendar days after the sponsor’s initial receipt of the 
information (21 CFR 312.32(c)(2)). 
7.4 
Reporting of Other Information - Unanticipated Problems 
As outlined by the Office for Human Research Protection, unanticipated problems must be 
reported to the IRB according to the requirements of 45 CFR Part 46. Unanticipated 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 53 of 80 
problems are considered to include any incident, experience, or outcome that meets ALL the 
following criteria: 
•
Unexpected (in terms of nature, severity, or frequency) given:
•
Procedures that are described in the study-related documents, such as the IRB
approved research protocol and informed consent document.
•
The characteristics of the participant population being entered into the study.
•
Related or possibly related to participation in the study which means there is a
reasonable possibility that the incident, experience, or outcome may have been caused
by the sample collection.
•
Suggests that the study places participants or others at a greater risk of harm
(including physical, psychological, economic, or social harm) than was previously
known or recognized.
An incidence, experience, or outcome that meets the three criteria above generally will 
warrant consideration of substantive changes in the study or informed consent 
process/document or other corrective actions in order to protect the safety, welfare, or rights 
of participants or others. Only a small subset of AEs occurring in human participants 
participating in a clinical study will meet these three criteria for an unanticipated problem. 
There are other types of incidents, experiences, and outcomes that occur during the conduct 
of a clinical study that represent unanticipated problems but are not considered AEs. For 
example, some unanticipated problems involve social or economic harm instead of the 
physical or psychological harm associated with AEs. In other cases, unanticipated problems 
place participants or others at increased risk of harm, but no harm occurs. 
The investigator should promptly notify the IRB when an unanticipated problem involving 
risks to participants or others is identified. Also, the investigator should notify the sponsor of 
unanticipated problem(s). 
7.5 
Follow-up of Adverse Events 
All SAEs/AESI/MAAEs/AEs will be followed until resolution, stabilization, or up to 30 days 
after the last study visit. 
7.5.1 Follow-up of Nonserious Adverse Events 
Nonserious AEs that are identified during the 28-day postvaccination period and still ongoing 
on the last scheduled visit must be recorded on the AE eCRF with the current status noted. 
All nonserious events that are ongoing at this time will be recorded as “Not Recovered/Not 
Resolved” on the AE eCRF. The status of ongoing, previously reported AEs will be subject 
to active follow-up. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 54 of 80 
7.5.2 Follow-up of Serious Adverse Events or Adverse Events of Special Interest 
This study requires that participants be monitored for SAE/AESI/MAAE up to Day 183 End 
of Study Visit. From Day 1 (Visit 2), confirmed SAEs, confirmed AESI, and confirmed 
MAAEs will be recorded on the AE eCRF.  
The investigator will provide or arrange appropriate care for participants for whom SAEs, 
potential AESI or MAAEs are reported. Withdrawal/discontinuation of participants from the 
study to treat SAEs/AESI/MAAEs are at the discretion of the investigator.  
All SAEs/AESI/MAAEs will be followed by the principal investigator (or designee) until one 
or the other condition is met: 
•
The event is resolved or stable if condition is expected to remain chronic.
•
The participant is referred to a specialist or other physician for treatment and follow-
up. The principal investigator (or designee) will follow the participant's condition
even if the participant is seen by another physician, to obtain information about the
diagnosis and outcome and any treatments and medications administered for the
event.
The following will be considered acceptable reasons for discontinuation of follow-up of 
ongoing SAEs: 
•
Participant withdraws consent.
•
Participant is referred to appropriate long-term medical care.
•
Participant is considered lost to follow-up.
It is expected that the clinical site will obtain supporting medical records from appropriate 
physicians and record and/or upload this information on the SAE Report Form within the AE 
eCRF. Additional information received related to any SAE must be added to the SAE Report 
Form within the AE eCRF or forwarded to the Emergent Global PV Department within 24 
hours of awareness (Section 7.3.1). 
7.6 
Safety Data Monitoring 
An independent SMC will be constituted under a separate charter. The SMC will review 
aggregated, blinded safety data after the 300th enrolled participant passes Day 29, and again 
after the last enrolled participant passes Day 29. 
Safety data in this study will also be reviewed on an ongoing basis by the sponsor’s MM as 
outlined in the study Medical Monitoring Plan.  
7.7 
Breaking the Blind for Individual Participants 
The blind may be broken if the health or safety of a participant is at risk and knowledge of 
the study arm may be beneficial to the medical management of the participant. The 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 55 of 80 
pharmacist, investigator or other authorized individual may receive the allocation of an 
individual participant in the event that unblinding is required. In such an event, the sponsor 
must be notified. 
If the investigator determines that knowledge of a participant’s treatment assignment is 
urgently needed to guide treatment or ensure the participant’s safety, the investigator may 
perform emergency unblinding via the RTSM system. The investigator may not delegate this 
responsibility. The investigator must attempt to notify the sponsor’s MM prior to unblinding 
and must notify the MM within 24 hours after unblinding at the latest. 
If a participant’s study treatment assignment is unblinded for safety reasons, or if a 
participant becomes accidentally unblinded for any reason, the participant will be requested 
to remain in the study for safety follow-up.  
The procedures to be followed in the event of an emergency unblinded for a medical 
emergency are outlined in the study pharmacy manual.   
8 
STATISTICAL CONSIDERATIONS 
8.1 
Sample Size Rationale 
8.1.1 Sample Size and Power for Immunogenicity 
The primary statistical comparison between the PXVX0317 and placebo treatment groups is 
based on the difference between treatment groups in seroresponse rate (proportion of 
participants with anti-CHIKV SNA NT80 
 as measured by the human SNA assay) at 
Day 22, which will be tested using a chi-square test with a two-sided alpha=0.05 in the IEP 
across all age groups combined. The analysis will be repeated for the mITT as a measure of 
the robustness of the result. 
Based on the data from the phase 2 study (protocol PXVX-CV-317-001) (16, 28), the 
seroresponse rate for PXVX0317 vaccine is expected to be approximately 
 vs <5% for 
the placebo participants at Day 22. With an assumed 10% rate of nonevaluable participants, 
the power to show superiority over placebo with 2430 PXVX0317 vaccine and 405 placebo-
evaluable participants is >99.9% for the combined ages groups. The power is 99% for each 
of the smaller 12 to <18 and 46 to <65 age groups with samples sizes of 189 vs 32 evaluable 
participants (PXVX0317: placebo).  
The difference in seroresponse rate between PXVX0317 and placebo groups that is 
considered clinically relevant is 
 With 2430 PXVX0317-treated participants and a target 
seroresponse rate of 
 vs a rate of 0% for placebo, the width of a two-sided 95% CI would 
be ±1.2%. The difference in seroresponse rate must be above 
 for the lower bound of the 
95% CI for the difference to be 
. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 56 of 80 
8.1.2 Sample Size and Power for Lot Consistency 
The second consideration for sizing the study is ensuring adequate power for the lot 
consistency equivalence intervals testing immunogenicity at Day 22, as measured by human 
SNA assay anti-CHIKV SNA GMT ratios between all three pairs of consecutively 
manufactured PXVX0317 lots (A:B, A:C, B:C) in the 18 to <46 years of age stratum for the 
IEP. Pairwise testing of lots will be performed without multiplicity adjustment, and for each 
GMT ratio the two-sided 95% confidence interval must fall within the equivalence interval of 
[0.667, 1.5] for the lots to be considered equivalent. 
On the log10 scale, two one-sided equivalence tests have 95% power to reject the null 
hypothesis that the difference in mean titers between lots is below -0.176 or above 0.176 in 
favor of an alternative hypothesis of equivalence when the expected difference in log10 
means is 0, the common SD is 0.455, each test is at the 2.5% level and the sample size in 
each lot is 207. The SD estimate was based on the upper bound of an 80% CI on the SD on 
the log10 scale observed in the human SNA assay on samples collected 4 weeks after 
participants were treated with a single dose of PXVX0317. To be conservative, at least 1050 
evaluable participants (300 participants in each lot along with 150 placebo participants) need 
to be enrolled into the 18 to <46 age group to provide adequate power for the lot consistency 
objective. 
8.1.3 Sample Size and Power for Adverse Events 
The final consideration for the sample size of the study is the size of the prelicensure safety 
database. With 2700 participants receiving any lot of PXVX0317, this study is 93.3% likely 
to detect at least one AE with a true frequency of ≥0.1% (ie, “uncommon”). 
8.2 
Analysis Populations 
Analysis will be based on the following study populations: 
Randomized Population: All screened participants who provide informed consent and 
provide demographic and other screening measurements and are randomized. 
Exposed Population: All participants in the randomized population who receive IP. 
Safety Population: All participants in the exposed population who provide safety assessment 
data. This generally includes anyone who was not lost to follow-up at Day 1 as they will be 
at risk for reporting an SAE. Participants will be analyzed as treated (ie, according to the 
treatment a participant received, rather than the treatment to which the participant may have 
been randomized). 
Modified Intent-to-Treat Population: All randomized participants who are vaccinated and 
have at least one post-injection anti-CHIKV SNA NT80 result. Participants are counted in the 
group to which they were randomized. 
Immunogenicity Evaluable Population: 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 57 of 80 
The IEP includes all participants in the mITT population who: 
•
Provide evaluable serum sample results for the relevant postvaccination time points,
and within the required time frames:
•
Day 22: Day 19 through Day 27, inclusive.
•
Have no measurable anti-CHIKV SNA at Day 1 (baseline).
•
Have no major protocol deviation or other reason to be excluded as defined prior to
unblinding.
Tables will be displayed by treatment group (PXVX0317 and placebo) columns with lots 
pooled with the exception of the lot consistency analysis, where the separate lots will be 
displayed.  
8.3 
Study Endpoints 
8.3.1 Primary Endpoints 
Safety Endpoints: 
•
Incidence of solicited AEs through Day 8 for PXVX0317 and placebo.
•
Incidence of unsolicited AEs through Day 29 for PXVX0317 and placebo.
•
Incidence of AESI, MAAEs and SAEs through Day 183 for PXVX0317 and placebo.
Coprimary Immunogenicity Endpoints: 
•
Difference in anti-CHIKV SNA seroresponse rate (PXVX0317 minus placebo) and
associated 95% CI at Day 22.
Success criterion: Lower bound of the two-sided 95% CI on the difference in 
seroresponse rates between PXVX0317 and placebo groups 
 (equivalent to a 
difference >0 using a two-sided chi-square test). 
Note: Seroresponse rate (considered the presumptive seroprotection rate) is defined as 
the percentage of participants who achieve an anti-CHIKV SNA titer 
 See Section 
6.1 for assay description. See Section 8.6 for immunogenicity analysis details and Section 
8.6.2.5 for success criteria and multiplicity controls. 
•
Anti-CHIKV SNA GMT and associated 95% CIs at Day 22 for PXVX0317 and
placebo.
Success criterion: Significant difference in the IEP across all age groups 
combined using an ANOVA model with logarithmically transformed anti-CHIKV 
SNA titers (log10) as the dependent variable and treatment group and study site as 
the fixed effects with a two-sided significance level of 0.05. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 58 of 80 
•
Anti-CHIKV SNA GMT ratio between all three pairs of PXVX0317 lots (A:B, A:C,
B:C) (adults 18 to <46 years of age) at Day 22.
Success criterion: Pairwise GMT ratios (A:B, A:C, B:C) each with a two-sided 
95% CI within [0.667; 1.5] for the IEP in the 18 to <46 years of years of age 
stratum using an ANOVA model with log10-transformed anti-CHIKV SNA titers 
as the dependent variable and vaccine lot and study site as the fixed effects to 
derive the GMT ratios. 
8.3.2 Secondary Endpoints 
•
Key secondary endpoints: Difference in anti-CHIKV SNA seroresponse rate
(PXVX0317 minus placebo) with associated 95% CI at Day 15, Day 183, and Day 8,
in that order (see Section 8.6.2.5).
Success criterion: At Day 15 only, lower bound of the two-sided 95% CI on the 
difference in seroresponse rates between PXVX0317 and placebo groups 
 
(equivalent to a difference >0 using a two-sided chi-square test). 
•
Anti-CHIKV SNA GMTs by study arm with associated 95% CIs at Day 8, Day 15,
and Day 183.
•
Geometric mean fold increase from Day 1 to subsequent collection time points.
•
Number and percentage of participants with an anti-CHIKV SNA titer ≥15 and 4-fold
rise over baseline.
8.3.3 Exploratory Endpoint 
•
Anti-CHIKV SNA seroresponse rate difference with associated 95% CIs for each pair
of PXVX0317 lots (A minus B, A minus C, B minus C) (adults 18 to <46 years of
age) at Day 22.
8.4 
Handling Missing Data
Participants with missing immunogenicity data at Days 8, 15, 22, or 183 will be excluded 
from the corresponding analysis; missing immunogenicity data will not be imputed. Human 
SNA assay values below the lower limit of quantitation (LLOQ) will be replaced by LLOQ/2 
in the immunogenicity analyses. Imputation rules for partial or missing dates will be 
described in the study statistical analysis plan (SAP). 
8.5 
Analysis of Disposition, Demographic and Baseline Characteristics 
Disposition will be summarized for all randomized participants. Demographic and baseline 
characteristics including age, sex, race, ethnicity, BMI, will be tabulated by treatment group 
for the randomized, safety, mITT, and IEP populations. Continuous endpoints will be 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 59 of 80 
summarized by descriptive statistics; categorical endpoints will be summarized by the 
number of participants, frequency counts, and percentages. 
Medical history will be coded to SOC and PT using the MedDRA dictionary and summarized 
by treatment group for the randomized population. Protocol deviations will be categorized as 
important or not important and evaluated for exclusion of data from analyses. They will be 
presented by treatment group for the randomized population. 
8.6 
Immunogenicity Analysis 
Summary statistics for immunogenicity results by scheduled visit for each treatment group 
will be provided for the IEP population, unless otherwise specified. In the analysis of the 
human SNA assay data as a continuous variable, anti-CHIKV SNA NT80 values will be 
logarithmically transformed (base10), and the GMTs and associated 95% CI for each 
treatment group will be computed by exponentiating the corresponding log-transformed 
means and two-sided 95% CIs. Results will be presented for all age groups combined as well 
as separately. Geometric mean fold increase will also be displayed by postvaccination 
scheduled visit for each treatment group. 
Proportions of participants with human SNA assay titer 
 and secondary response rates at 
other titers (eg, 15 and 4-fold rise over baseline) will be reported with associated two-sided 
95% Wilson method CIs by scheduled visit for each treatment group. 
Reverse cumulative distribution plots of human SNA assay vs proportion of participants in 
each treatment group will be generated by scheduled visit. Geometric mean titer will also be 
plotted over time for each treatment group. 
8.6.1 Coprimary Immunogenicity Analysis 
The familywise error rate will be fixed at a two-sided alpha of 0.05 by the requirement that 
all coprimary endpoint hypotheses must be met for a successful outcome: Day 22 
seroresponse (titer of 
 Day 22 GMT, and lot consistency pairwise GMT ratios, each 
discussed below (see Section 8.6.2.5). Note that success on the Day 22 lot consistency 
endpoint is only required for FDA. 
8.6.1.1 
Day 22 Seroresponse Rate Analysis  
The superiority of the immune response to PXVX0317 vaccine over that to placebo will be 
demonstrated at Day 22 by comparing seroresponse rates between the two treatment groups 
(the proportion of participants with a human SNA assay 
 considered the presumptive 
seroprotection rate). The difference in seroresponse rates between the PXVX0317 and 
placebo groups will be calculated, along with the 95% CI for the difference based on the 
Newcombe hybrid score method. The lower bound of the two-sided 95% CI on the difference 
in seroresponse rates between PXVX0317 and placebo groups must be 
. Additionally, 
the null hypothesis of no difference between seroresponse rate proportions will be tested 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 60 of 80 
using a chi-square test with alpha=0.05. No multiplicity adjustment will be employed (see 
Section 8.6.2.5), and no covariate adjustment will be performed. 
The primary comparison will be in the IEP across all age groups combined. Tests will be 
repeated in the mITT population as a measure of robustness, along with tests for each 
population in the separate age strata. No multiplicity adjustment will be made for the analysis 
of the separate age strata as the primary population will be the combined age groups. 
8.6.1.2 
Day 22 Geometric Mean Titer Analysis 
In addition, Day 22 GMTs will be compared between PXVX0317 and placebo treatment 
groups and will be analyzed via a linear model based on an alpha=0.05. The primary model is 
an ANOVA, with logarithmically transformed anti-CHIKV SNA titers (log10) as the 
dependent variable and treatment group and study site as the fixed effects in the model. The 
adjusted least square means and their 95% CIs calculated based on the ANOVA will be back 
transformed and reported as the group GMT values. All tests will be carried out at a two-
sided significance level of 0.05 and no adjustment for multiplicity will be applied (see 
Section 8.6.2.5).  
The primary comparison will be in the IEP across all age groups combined. Tests will be 
repeated in the mITT population as a measure of robustness, along with tests for each 
population in the separate age strata. No multiplicity adjustment will be made for the analysis 
of the separate age strata as the primary population will be the combined age groups. 
8.6.1.3 
Day 22 Lot Consistency Analysis 
The consistency of the immune response across three consecutively manufactured lots of 
PXVX0317 vaccine will be confirmed at Day 22. Immunogenicity as measured by human 
SNA assay anti-CHIKV SNA GMTs will be compared using ratios of GMTs between all 
three pairs of PXVX0317 lots (A:B, A:C, B:C) for the IEP in the 18 to <46 years of age 
stratum, and the analysis will be repeated for the mITT population as a measure of the 
robustness of the results.  
The GMTs associated with the primary lot consistency objective will also be calculated via a 
linear model for the anti-CHIKV SNA titers collected at Day 22. The primary model is an 
ANOVA, with log10-transformed anti-CHIKV SNA titers as the dependent variable and 
vaccine lot and study site as the fixed effects in the model. The adjusted least square means 
and their 95% CIs calculated based on the ANOVA will be back transformed and reported as 
the vaccine lot GMT values. The ratio of GMTs for the comparison of the three pairs of 
PXVX0317 lots (A:B, B:C, A:C) will be derived from this model. 
All tests will be carried out at a two-sided significance level of 0.05 and no adjustment for 
multiplicity will be applied (see Section 8.6.2.5). If for all pairs of vaccine lots, the two-sided 
95% CI of the GMT ratio is within [0.667; 1.5] then lot-to-lot consistency will be 
demonstrated.   

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 61 of 80 
The seroresponse rates for each vaccine lot at Day 22 also will be assessed, but as an 
exploratory endpoint, as outlined in Section 8.3.3. 
8.6.2 Secondary Immunogenicity Analysis 
8.6.2.1 
Key Secondary Immunogenicity Analyses: Seroresponse Rate and 
Seroresponse Rate Difference at Days 15, 183, and 8, in that Order 
Seroresponse rates and seroresponse rate differences (PXVX0317 minus placebo) with 
associated 95% CIs based on antibody titers measured at Days 15, 183, and 8 will be 
analyzed as described above for Day 22 (see Section 8.6.2.5 for multiplicity controls). For 
each time point, the null hypothesis of no difference between seroresponse rate proportions in 
the PXVX0317 vs placebo group will be tested using a chi-square test with alpha=0.05. For 
Day 15 only, the lower bound of the two-sided 95% CI on the difference in seroresponse 
rates between PXVX0317 and placebo will be compared to 
 for assessment of clinical 
significance.  
8.6.2.2 
Geometric Mean Titer at Days 8, 15, and 183 
For the comparison of PXVX0317 to placebo, GMTs based on antibody titers measured at 
Days 8, 15, and 183 will be analyzed as described above for Day 22. Geometric mean fold 
increases for increase over Day 1 titer will be analysed as described for GMTs for each 
postvaccination time point.  
8.6.2.3 
Seroconversion at Other Titers 
As described above, secondary response rates at other titers (eg, 15 and 4-fold rise over 
baseline) will be reported with associated two-sided 95% Wilson method CIs by scheduled 
visit for each treatment group. 
8.6.2.4 
Immunogenicity Analysis in Adolescents and Older Adults 
As noted above, the immunogenicity analyses will include separate evaluations of 
seroresponse rate and GMT for each age group in addition to the overall study participant 
population.   
8.6.2.5 
Multiplicity Controls 
8.6.2.5.1 
Coprimary Immunogenicity Endpoints 
The familywise error rate will be fixed at a two-sided alpha of 0.05 by the requirement that 
all coprimary immunogenicity endpoints must be met for a successful outcome: 
1. Day 22 seroresponse in the IEP across all age groups combined, including superiority
to placebo and the success criterion of the lower bound of the two-sided Newcombe

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 62 of 80 
hybrid score method 95% CI on the difference in seroresponse rates between 
PXVX0317 and placebo 
. 
2. Day 22 GMTs significantly different between PXVX0317 and placebo in the IEP
across all age groups combined using an ANOVA model with logarithmically
transformed anti-CHIKV SNA titers (log10) as the dependent variable and treatment
group and study site as the fixed effects with a two-sided significance level of 0.05.
3. Day 22 lot consistency pairwise GMT ratios (A:B, A:C, B:C) each with a two-sided
95% CI within [0.667; 1.5] for the IEP in the 18 to <46 years of years of age stratum
using an ANOVA model with log10-transformed anti-CHIKV SNA titers as the
dependent variable and vaccine lot and study site as the fixed effects to derive the
GMT ratios. Note that success on the Day 22 lot consistency endpoint is only
required for FDA.
8.6.2.5.2 
Key Secondary Immunogenicity Endpoints 
A prespecified hierarchical approach will be employed for the key secondary 
immunogenicity endpoint hypothesis testing to preserve the type I error rate without the need 
for further multiplicity adjustment. If the null hypotheses are rejected for all coprimary 
endpoints, only then will the key secondary endpoints be formally tested in sequential order. 
If a nonsignificant test is reached formal testing will stop, and the remaining endpoints will 
be reported for information only. The seroresponse rates and rate differences at Days 15, 183, 
and 8 will be tested sequentially in order, each for the IEP across all age groups combined, as 
follows: 
1. Day 15 seroresponse superior to placebo and the success criterion of the lower bound
of the two-sided Newcombe hybrid score method 95% CI on the difference in
seroresponse rates between PXVX0317 and placebo 
.
2. Day 183 seroresponse superior to placebo.
3. Day 8 seroresponse superior to placebo.
After testing the coprimary immunogenicity endpoints and, if all met, the hierarchical key 
secondary immunogenicity endpoints, no other formal hypothesis testing will be carried out. 
The remaining secondary immunogenicity endpoints including GMTs, GMFI, other titers, 
the exploratory endpoint, and all safety endpoints will be evaluated and reported for 
information only, thus no further multiplicity adjustment is needed. 
8.7 
Safety Analysis 
The safety of PXVX0317 in healthy adult and adolescent participants 12 to <65 years of age 
will be evaluated using solicited AEs occurring from IP administration on Day 1 until Day 8 
and unsolicited AEs through Day 29, AESI, MAAEs, and SAEs though Day 183 End of 
Study Visit, and vital signs. Solicited AEs include local (i.e., pain, redness, and swelling) and 
systemic reactions (i.e., fever, chills, fatigue, headache, myalgia, arthralgia, and nausea). 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 63 of 80 
8.7.1 Exposure 
The frequencies and percentages of participants treated will be summarized by treatment 
group for the randomized population. 
All safety analyses will be based on the safety population. 
8.7.2 Adverse Events 
Adverse events will be coded to SOC and PT using the MedDRA dictionary. Solicited AEs, 
unsolicited AEs, AESI, MAAEs, and SAEs will be summarized separately by treatment 
group and maximum severity for the safety population for all age strata combined as well as 
for separate age groups. 
8.7.2.1 
Solicited Adverse Events 
With the exception of redness and swelling, all solicited AEs will be summarized according 
to severity grading scales defined in Section 7.1.7 from “mild” to “potentially life-
threatening.” 
Solicited AEs will be recorded daily until 7 days post-injection (Day 8) using an e-diary. The 
analyses of solicited AEs will be performed by maximum severity and by treatment group. In 
addition, solicited AEs ongoing after seven days post-injection (Day 8) will also be recorded 
as unsolicited AEs. 
Frequencies and percentages of participants experiencing each solicited AE will be presented 
by maximum severity. Summary tables showing the occurrence of any local or any systemic 
solicited AE overall and at each time point will also be presented. 
The severity of redness and swelling, recorded as diameters (mm), will be summarized 
according to categories based on the largest diameter linear measurement when the local 
reaction is present:  
•
Grade 0/absent = 0-24 mm
•
Grade 1/mild = 25-50 mm
•
Grade 2/moderate = 51-100 mm
•
Grade 3/severe = >100 mm
•
Grade 4/potentially life threatening = necrosis or exfoliative dermatitis
Refer to Appendix I. 
Events reported as not present (0 mm is entered) will be reported as Grade 0. 
The following summaries of solicited events will be performed: 
1. Solicited events by day post-injection for each event and for any event.
2. Time of first onset of solicited AEs, for each event and any event.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 64 of 80 
3. Solicited AEs by maximum event severity, for each event and for any event.
4. Duration of solicited AEs, for each event and any event.
Solicited AEs, occurrence of at least one event by category (local, systemic), will also be 
included.  
Only participants with at least one observation (i.e., any nonmissing values but excluding 
“Not done/unknown”) for the solicited AEs will be summarized.  
8.7.2.2 
Unsolicited Adverse Events 
All the unsolicited AEs occurring during the proscribed collection period in the study, will be 
recorded, regardless of their assessment of relatedness by the investigator. 
The original verbatim terms used by investigators to identify AEs in the eCRFs will be 
mapped to PT using the MedDRA dictionary. The unsolicited AEs will then be grouped by 
MedDRA PT into frequency tables according to SOC. All reported AEs, as well as AEs 
judged by the investigator as at least possibly related to IP, will be summarized by treatment 
group, according to SOC and PT. When an unsolicited AE occurs more than once for a 
participant, the maximum severity and strongest relationship to the treatment group will be 
counted. 
Only treatment-emergent AEs will be summarized (i.e., excluding those after a participant 
has given informed consent, but before vaccination).  
Unsolicited AEs will be summarized by alphabetic SOC and preferred term as follows: 
•
Any unsolicited AE
•
Related (“possibly” or “probably” related) unsolicited AEs
•
Serious adverse events
•
Related (“possibly” or “probably” related) SAEs
•
Adverse events of special interest
•
Medically-attended AEs
•
Related MAAEs
•
Unsolicited AEs leading to withdrawal
•
Any AE leading to death
Listings of all AEs will be provided by participant. 
Combined solicited and unsolicited AEs: Solicited AEs continuing beyond 7 days after 
vaccination will be coded by MedDRA and combined with the unsolicited AEs. A summary 
of participants with all combined solicited and unsolicited AEs, by SOC and PT, will also be 
provided. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 65 of 80 
8.7.3 Clinical Laboratory Data 
No clinical safety laboratory data will be collected in this study. 
8.7.4 Physical Examinations 
Physical examinations by body system include a complete examination at screening and 
directed examinations at Days 1, 8, 15, 22, and 183. Physical examination data will be listed. 
8.7.5 Vital Signs 
Vital signs including temperature, blood pressure, respiratory rate, and heart rate at screening 
and pre- and postvaccination on Day 1 will be summarized by treatment group. 
8.7.6 Prior and Concomitant Medications 
Prior and concomitant medications will be coded to preferred drug name using the World 
Health Organization DRUG dictionary and summarized by treatment group for the safety 
population. 
8.7.7 Other Safety Variables 
None. 
8.7.8 Subgroup Analysis 
Except for lot consistency analyses, PXVX0317 lots will be pooled as the PXVX0317 
treatment group. Summaries will pool all age groups and will be repeated separately for each 
age group. Analyses of the primary immunogenicity and safety endpoints will also be 
summarized by sex, race, and ethnicity along with treatment group. 
8.7.9 Interim Analysis 
No formal interim analysis is planned. The SMC (Section 7.6) will review aggregated, 
blinded safety data after the 300th enrolled participant passes Day 29, and again after the last 
enrolled participant passes Day 29.  
9 
DATA HANDLING AND RECORD KEEPING 
9.1 
Source Documents and Access 
Source data are all information, original records of clinical findings, and observations in a 
clinical study necessary for the reconstruction and evaluation of the study. The source 
documentation requirements described below apply to all source documentation and study 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 66 of 80 
records in any form, including those maintained in the institution’s electronic health record 
system, if applicable. 
The investigator/institution will maintain adequate and accurate source documents and study 
records that include all pertinent information related to participants’ participation in the 
study, including details but not limited to signed and dated notes on consenting, eligibility, 
medical history, study assessments, IP administration, AEs, concomitant medications, 
participant follow-up information and other relevant observations. 
Source data should be attributable, legible, contemporaneous, original, accurate, and 
complete. Changes to source data should be traceable, should not obscure the original entry 
and should be explained if necessary (eg, via an audit trail). 
The investigator/institution shall permit study-related monitoring, audits, IRB review, and 
regulatory inspection(s), providing direct access to source data/documents.  
Records from the study that identify the participant will be confidential except that they may 
be given to and inspected by sponsor (or designee), the IRB, the FDA, EMA, and other 
government agencies as appropriate and will not otherwise be released except as required by 
law. All information provided to the investigator by the sponsor is to be considered 
confidential unless otherwise stated. 
9.2 
Data Management 
A validated, EDC system will be used during the study. Data management activities to be 
performed for the study will be described in detail in the Data Management Plan (DMP) 
documents.  
9.3 
Data Collection and Discrepancy Management 
Data collected during the study will be recorded in the eCRFs designed for this study. 
Investigational sites will have the responsibility for capturing and maintaining accurate eCRF 
data, records, and relevant source documentation, as well as conforming to procedures 
established by the sponsor around system access/security and ensuring a data audit/edit trail 
for data corrections. All source documents will be verified by the study monitor for accuracy. 
Information from external sources such as laboratory data, images, etc. as defined in this 
protocol will be collected and maintained outside the EDC and reconciled with the eCRF 
data periodically (as applicable). As data are entered into the eCRF, automated edit checks 
will validate data. Additionally, manual reviews will be performed for data discrepancy by 
the monitor and queries will be generated into the EDC system. After clinical sites respond to 
queries and data corrections are made and reviewed by the monitor, the investigator will 
review and electronically sign the eCRF for each participant. The sponsor will review data 
for accuracy, completeness, and consistency during the conduct of the study and prior to 
database lock. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 67 of 80 
For further information on eCRFs, refer to the CRF Completion Guidelines. Details on data 
handling will be described in the DMP. 
9.4 
Laboratory Data 
No external laboratory data transfers will be done. Sites will manually enter results for 
HBsAg/HCV antibody/HIV-1/HIV-2, HCV RNA (when applicable), and pregnancy testing 
into applicable eCRFs. Anti-CHIKV SNA titer results will be handled by the sponsor. 
9.5 
File Management at the Investigational Site 
The investigator will ensure that the study site file is maintained in accordance with the ICH 
GCP guidelines and as required by applicable local regulations. The investigator/institution 
will take measures to prevent accidental or premature destruction of these documents. 
9.6 
Records Retention at the Investigational Site 
Per ICH GCP guidelines, study documents will be retained for one of the following periods: 
•
A period of at least two years after the date of the last approval of a marketing
application in an ICH region until there are no pending or contemplated marketing
applications.
•
A period of at least two years after the sponsor has notified the regulatory
authority(ies) that clinical investigation with this product is discontinued.
The investigator must not dispose of any records relevant to this study without either (1) 
written permission from the sponsor or (2) provision of an opportunity for the sponsor to 
collect such records. The investigator will be responsible to maintain adequate and accurate 
electronic or hard copy source documents of all observations and data generated during this 
study, including any data queries received from the sponsor (or designee). Such 
documentation is subject to inspection by the sponsor (or designee) and relevant regulatory 
agencies. If the investigator withdraws from the study (eg, due to relocation or retirement), 
all study-related records will be transferred to a mutually agreed upon designee within a 
sponsor-specified timeframe. Notice of such transfer will be given to the sponsor in writing. 
9.7 
Deviations from the Protocol 
The principal investigator agrees to conduct the clinical study in compliance with the 
protocol agreed to by the sponsor and approved by the site’s IRB. 
A protocol deviation is defined as a site personnel or a study participant’s departure from the 
protocol requirements, whether inadvertent or planned. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 68 of 80 
The investigator or site staff may not deviate from the protocol, except, in rare 
circumstances, as necessary to eliminate immediate hazards to study participants. In such 
event, both the sponsor and IRB will be immediately notified.  
The occurrence of protocol deviations will be routinely monitored for, by evaluation of 
investigator compliance with the protocol, GCP, and regulatory requirements. The sponsor 
will review all protocol deviations on an ongoing basis and will be responsible for 
determining if the deviation should be categorized as an important protocol deviation. 
Important protocol deviations may require additional documentation as requested by the 
sponsor. 
Continued protocol deviations despite re-education of investigational site personnel, or 
persistent protocol deviations that are reportable to regulatory agencies may result in 
discontinued shipment of IP and termination of further enrollment at the investigational site, 
or termination of the investigational site from the study. 
10 QUALITY CONTROL AND ASSURANCE 
10.1 
Monitoring 
The assigned clinical study monitor will verify eCRFs entries against source documentation 
at regular intervals throughout the study to verify adherence to the protocol; completeness, 
accuracy, and consistency of the data; and adherence to ICH GCP guidelines and local and 
federal regulations applicable to the conduct of the clinical study. The investigator must 
make source documentation accessible to the study monitor as needed to verify the 
information in the eCRFs. The investigator agrees to meet with the study monitor at regular 
intervals to discuss study progress and ensure that any problems detected in the course of 
data monitoring are resolved appropriately. 
10.2 
Auditing 
The sponsor’s Quality Assurance Department (or designee) may conduct investigational site 
audits before study initiation, during the study, or after study completion, as documented in 
the Clinical Quality Oversight Plan. Audits will include, but are not limited to, review of 
drug supply, presence of required documents, informed consent process, and comparison of 
eCRFs with source documents. The investigator agrees to participate in site audits and assist 
in the prompt resolution of any issues found during audits. 
Regulatory authorities or the IRB may inspect the investigational site during or after the 
study. The investigator will cooperate with such inspections and will contact the sponsor 
immediately if such an inspection occurs. 
In the event the investigator is contacted by a regulatory agency in relation to this study, the 
investigator and investigational site staff must be available to respond to reasonable requests 
and inspection queries made during the inspection process. The investigator must provide the 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 69 of 80 
sponsor with copies of all correspondence that may affect the review of the current study (eg, 
Form FDA 483, inspectional observations, warning letters). The sponsor will provide any 
needed assistance in responding to regulatory inspections. 
11 ETHICS AND RESPONSIBILITY 
This study must be conducted in accordance with the ethical principles that have their origin 
in the Declaration of Helsinki and in compliance with the protocol, current ICH GCP 
guidelines, national regulatory authorities, and all other applicable local laws and regulatory 
requirements. Each investigational site will seek approval by an IRB according to regional 
requirements. The IRB will evaluate the ethical, scientific, and medical appropriateness of 
the study. Further, in collecting and handling participant data and completing eCRFs, the 
investigator and investigational site staff will take measures to ensure adequate care in 
protecting participant privacy. To this end, a participant identification number will be used to 
identify each participant. 
11.1 
Informed Consent/Assent 
The investigator must obtain written informed consent from study participants prior to 
starting any study-related activities. For adolescent participants 12 to <18 years of age, the 
investigator must obtain both written informed consent from study participant’s parent or 
legal guardian and assent from the adolescent participant prior to starting any study-related 
activities. Emancipated or mature minors (defined by local laws) may be capable of giving 
autonomous consent. Adolescents reaching 18 years of age during the study must provide 
written informed consent as adults at the next study visit. All prospective participants (and/or 
legal guardian or legally authorized representative) must sign and date an IRB-approved ICF 
or assent form. 
11.2 
Institutional Review Board 
Before the start of the study, the Investigator’s Brochure (IB), the protocol, proposed 
informed consent form(s), participant compensation (if any), sponsor-approved study 
materials and advertisements, and any other written information to be provided to the 
participant, will be submitted to a properly constituted IRB for review. The sponsor must 
receive a copy of the written approval from the IRB for all of the above applicable 
documents prior to recruitment of participants into the study and shipment of IP. 
The IRB must provide written approval for all amendments to any of the above documents 
prior to implementation of these amendments at the investigational site.  
The names (or title, if IRB procedures prohibit publishing of names) and associated 
backgrounds of the members of IRB (to assist in assuring that the board membership is 
properly constituted and operates according to 21 CFR part 56) will be given to the sponsor 
prior to the start of the study along with a signed and dated statement stating that the protocol 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 70 of 80 
and ICF and, where applicable, any other document listed above, have been approved by 
them. 
All correspondence between the investigator and the IRB will be available for review by the 
sponsor (or designee), and the applicable regulatory authority(ies). 
11.3 
Compensation for Injury 
The sponsor will adhere to local regulations and guidelines regarding clinical study 
compensation to participants whose health is adversely affected by taking part in the study. 
The applicable policy for compensation for injury will be described in the ICF. 
11.4 
Participant Confidentiality 
The investigator must ensure the anonymity of each participant is maintained at all times. 
Participants should only be identified by their participant study ID number on the CRF or on 
any other study documents provided to the sponsor (or designee). Biospecimens should only 
be identified by sample numbers/codes as specified in the Laboratory Manual. Any 
documents that identify the participant should be kept in strict confidence by the study site.  
Based on ICH GCP guidelines and regulatory requirements, the principal investigator is 
required to allow authorized personnel of the sponsor (or designee), the IRB, and members of 
the appropriate regulatory authority(ies) to review participant’s files that are related to EBSI-
CV-317-004. Participants must be informed that their records may be reviewed by the 
sponsor (or designee), the IRB, and the appropriate regulatory authority(ies) through direct 
access to the participant’s original medical records. 
11.5 
Future Use of Stored Samples 
Any remnant (leftover) blood samples collected for the anti-CHIKV SNA analysis will be 
retained for future testing. Specimens will be identified by sample numbers/codes, thereby 
maintaining blinding while in storage. Participants will be asked to consent to the future use 
of these samples as part of the informed consent process.  
Samples may be retained for at least two years after the last approval of a marketing 
application in an ICH region and until there are no pending or contemplated marketing 
applications in an ICH region or until at least two years have elapsed since the formal 
discontinuation of clinical development. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 71 of 80 
12 ADMINISTRATIVE AND LEGAL REQUIREMENTS 
12.1 
Sponsorship 
This clinical study is sponsored by Emergent Travel Health Inc. 
. The manufacturer of PXVX0317 is Emergent 
BioSolutions Inc.  
12.2 
Protocol Amendments 
Protocol amendments will only be made by the sponsor. In general, any change to the 
protocol must be made in the form of a formal amendment to the protocol and must be 
approved in writing by the principal investigator, the sponsor, and the IRB prior to 
implementation. The investigator must receive written IRB approval for all protocol 
amendments prior to implementing protocol amendments at the study site. The investigator 
must send a copy of any IRB correspondence and all approval/disapproval letters from the 
IRB to the sponsor. 
A protocol change intended to eliminate an apparent immediate hazard to participants will be 
implemented immediately, followed by IRB notification within five working days.  
The sponsor will submit protocol amendments to the applicable regulatory authority(ies). 
12.3 
Clinical Study Registration 
For purposes of clinical study registration including reporting to ClinicalTrials.gov, the 
sponsor is the responsible party and will provide information regarding this study in 
accordance with applicable regulations. 
12.4 
Publication Policy 
Following the completion of the study, the data may be considered for reporting at a 
scientific meeting or for publication in a scientific journal. In these cases, the sponsor will be 
responsible for these activities and may work with the investigator(s) to determine how the 
manuscript is written and edited, the number and order of authors, the publication to which it 
will be submitted and other related issues. The sponsor has final approval authority over all 
such issues.  
Any proposed publication will be subject to review conditions and timelines agreed between 
the sponsor and the site investigator and detailed in the agreements with these parties prior to 
the start of the study. The sponsor will also post the results of the clinical study on 
ClinicalTrial.gov in a period no greater than 12 months from the completion of the study, 
defined as the time the final participant was examined or received an intervention for 
purposes of final collection of data for the primary outcome. 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 72 of 80 
Data are the property of the sponsor and cannot be published without prior authorization 
from the sponsor, but data and publication thereof will not be unduly withheld. 
All publication rights are delineated in the clinical trial agreement. 
12.5 
Terminating the Study 
The sponsor and/or the principal investigator may elect to terminate the study early as 
defined by the clinical trial agreement. The sponsor reserves the right to terminate the study 
at any time for clinical or administrative reasons. Any decision to voluntarily suspend or 
terminate a clinical study will be carefully reviewed and fully justified. The sponsor will 
notify the FDA and the IRB of any suspension or termination and provide the justification. 
The principal investigator must notify the IRB in writing of the study’s completion or early 
termination. The sponsor must receive a copy of the notification letter from the IRB 
indicating receipt of the completion or early termination letter. 
12.6 
Terminating the Study at an Individual Site 
A study site may be terminated from the study at the discretion of the principal investigator, 
the sponsor, or IRB. The sponsor may decide to replace a terminated site. 
13 REFERENCES 
1.
Ross RW. The Newala epidemic. III. The virus: isolation, pathogenic properties and
relationship to the epidemic. J Hyg (Lond). 1956;54(2):177-91.
2.
Powers AM, Logue CH. Changing patterns of chikungunya virus: re-emergence of a
zoonotic arbovirus. J Gen Virol. 2007;88(Pt 9):2363-77.
3.
CDC. Geographic Distribution: countries and territories where chikungunya cases have
been reported (as of October 30, 2020) 2020 [Available from:
https://www.cdc.gov/chikungunya/geo/.
4.
Contopoulos-Ioannidis D, Newman-Lindsay S, Chow C, LaBeaud AD. Mother-to-child
transmission of Chikungunya virus: a systematic review and meta-analysis. PLoS Negl
Trop Dis. 2018;12(6):e0006510.
5.
Borgherini G, Poubeau P, Staikowsky F, Lory M, Le Moullec N, Becquart JP, et al.
Outbreak of chikungunya on Reunion Island: early clinical and laboratory features in 157
adult patients. Clin Infect Dis. 2007;44(11):1401-7.
6.
Pialoux G, Gauzere BA, Jaureguiberry S, Strobel M. Chikungunya, an epidemic
arbovirosis. Lancet Infect Dis. 2007;7(5):319-27.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 73 of 80 
7.
Taubitz W, Cramer JP, Kapaun A, Pfeffer M, Drosten C, Dobler G, et al. Chikungunya
fever in travelers: clinical presentation and course. Clin Infect Dis. 2007;45(1):e1-4.
8.
Schilte C, Staikowsky F, Couderc T, Madec Y, Carpentier F, Kassab S, et al.
Chikungunya virus-associated long-term arthralgia: a 36-month prospective longitudinal
study. PLoS Negl Trop Dis. 2013;7(3):e2137.
9.
Amaral JK, Bilsborrow JB, Schoen RT. Brief report: the disability of chronic
chikungunya arthritis. Clin Rheumatol. 2019;38(7):2011-4.
10.
EBSI. PXVX-EPI-CV-001 Pediatric dengue cohort study in Nicaragua 2019.
11.
Yoon IK, Alera MT, Lago CB, Tac-An IA, Villa D, Fernandez S, et al. High rate of
subclinical chikungunya virus infection and association of neutralizing antibody with
protection in a prospective cohort in the Philippines. PLoS Negl Trop Dis.
2015;9(5):e0003764.
12.
Chang LJ, Dowd KA, Mendoza FH, Saunders JG, Sitar S, Plummer SH, et al. VRC 311:
safety and tolerability of chikungunya virus-like particle vaccine in healthy adults: a
phase 1 dose-escalation trial. Lancet. 2014;384(9959):2046-52.
13.
Ledgerwood J. VRC 311: a phase 1 open label, dose-escalation clinical trial to evaluate
the safety and immunogenicity of a virus-like particle (VLP) chikungunya vaccine, VRC-
CHKVLP059-00-VP, in healthy adults. ClinicalTrials.gov: National Institutes of Health
Clinical Center (CC) ( National Institute of Allergy and Infectious Diseases (NIAID)
2016 [Available from: https://clinicaltrials.gov/ct2/show/record/NCT01489358].
14.
Chen G, Ledgerwood, J. VRC 704: phase 2 randomized, placebo-controlled trial to
evaluate the safety and immunogenicity of a chikungunya virus-like particle vaccine,
VRC-CHKVLP059-00-VP, in healthy adults. ClinicalTrials.gov: ClinicalTrials.gov
Identifier: NCT02562482; 2019 [Available from:
https://clinicaltrials.gov/ct2/show/record/NCT02562482?term=VRC+704&rank=1.
15.
Chen GL, Coates EE, Plummer SH, Carter CA, Berkowitz N, Conan-Cibotti M, et al.
VRC 704: effect of a chikungunya virus-like particle vaccine on safety and tolerability
outcomes: a randomized clinical trial. JAMA. 2020;323(14):1369-77.
16.
Bennett S. PXVX-CV-317-001 A phase 2 parallel-group, randomized, double-blind study
to assess the safety and immunogenicity of PXVX0317 (chikungunya virus virus-like
particle vaccine [CHIKV-VLP], unadjuvanted or alum-adjuvanted).
ClinicalTrials.gov2018 [Available from:
https://clinicaltrials.gov/ct2/show/NCT03483961.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 74 of 80 
17.
Bennett S. EBSI-CV-317-002 A phase 2 open-label study to assess the safety and
immunogenicity of an alum-adjuvanted chikungunya virus-like particle vaccine
(PXVX0317) in prior recipients of other alphavirus vaccines (WRAIR).
ClinicalTrials.gov: United States National Library of Medicine 2020 [A phase 2 open-
label study to assess the safety and immunogenicity of an alum-adjuvanted chikungunya
virus-like particle vaccine (PXVX0317) in prior recipients of other alphavirus vaccines
versus alphavirus naïve controls.]. Available from:
https://www.clinicaltrials.gov/ct2/show/NCT03992872.
18.
Mendy J. Poster: Plaque reduction luciferase-based assay (CHIKV-luc). 2016.
19.
Morens DM, Fauci AS. Chikungunya at the door--deja vu all over again? N Engl J Med.
2014;371(10):885-7.
20.
CDC. Chikungunya Geographic Distribution [Available from:
https://www.cdc.gov/chikungunya/geo/index.html.
21.
CDC. Chikungunya Nowcast for the Americas: Centers for Disease Control and
Prevention; 2020 [Available from:
https://www.cdc.gov/chikungunya/modeling/index.html.
22.
CDC. Chikungunya virus in the United States 2013-2019: Centers for Disease Control
and Prevention 2020 [Available from: https://www.cdc.gov/chikungunya/geo/united-
states.html.
23.
Lindsey NP, Prince HE, Kosoy O, Laven J, Messenger S, Staples JE, et al. Chikungunya
virus infections among travelers-United States, 2010-2013. Am J Trop Med Hyg.
2015;92(1):82-7.
24.
Ruiz-Moreno D, Vargas IS, Olson KE, Harrington LC. Modeling dynamic introduction
of chikungunya virus in the United States. PLoS Negl Trop Dis. 2012;6(11):e1918.
25.
Evans D, Meires, JL. Chikungunya Virus: a rising health risk in the United States and
how nurse practitioners can help address and reduce the risk. The Journal for Nurse
Practitioners. 2016;12(5):289-98.
26.
Del Valle SY, McMahon BH, Asher J, Hatchett R, Lega JC, Brown HE, et al. Summary
results of the 2014-2015 DARPA Chikungunya challenge. BMC Infect Dis.
2018;18(1):245.
27.
CDC. Vaccine Recommendations and Guidelines of the ACIP: Centers for Disease
Control and Prevention; 2020 [TABLE 6-2. Needle length and injection site of IM
injections for children aged ≤18 years (by age) and adults aged ≥9 years (by sex and

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 75 of 80 
weight)]. Available from: https://www.cdc.gov/vaccines/hcp/acip-recs/general-
recs/administration.html. 
28.
EBSI. Emergent Travel Health Inc. Data on File. 2020.

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 76 of 80 
APPENDIX I 
TOXICITY GRADING SCALE TABLES 
Local Reaction to 
Injectable Product 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Pain 
Does not interfere 
with activity 
Repeated use of 
non-narcotic pain 
reliever >24 hours 
or interferes with 
activity 
Any use of 
narcotic pain 
reliever or 
prevents daily 
activity 
Emergency room 
(ER) visit or 
hospitalization 
Tenderness 
Mild discomfort to 
touch 
Discomfort with 
movement 
Significant 
discomfort at rest 
ER visit or 
hospitalization 
Erythema/Redness* 
25 – 50 mm*** 
51 – 100 mm*** 
>100 mm***
Necrosis or 
exfoliative 
dermatitis 
Induration/Swelling** 
25 – 50 mm*** 
and does not 
interfere with 
activity 
51 – 100 mm*** 
or interferes with 
activity 
>100 mm*** or
prevents daily
activity
Necrosis 
*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.
***Revised by the sponsor
Vital Signs* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
 (Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Fever (°C)** 
 (°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
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) – mmHg 
141 – 150 
151 – 155 
>155
ER visit or 
hospitalization for 
malignant 
hypertension 
Hypertension 
(diastolic) – mmHg 
91 – 95 
96 – 100 
>100
ER visit or 
hospitalization for 
malignant 
hypertension 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 77 of 80 
Vital Signs* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
 (Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Hypotension 
(systolic) – mmHg 
85 – 89 
80 – 84 
<80 
ER visit or 
hospitalization for 
hypotensive shock 
Respiratory Rate – 
breaths per minute 
17 – 20 
21 – 25 
>25
Intubation 
*Participant should be at rest for all vital sign measurements.
**Oral temperature; no recent hot or cold beverages or smoking.
***When resting heart rate is between 60 – 100 beats per minute. Use clinical judgement when
characterizing bradycardia among some healthy participant populations, for example, conditioned athletes.
Systemic 
(General) 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
 (Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Nausea/vomiting 
No interference 
with activity or 1 – 
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 
Diarrhea 
2 – 3 loose stools 
or <400 g/24 hours 
4 – 5 stools or 400 
– 800 g/24 hours
6 or more watery 
stools or >800 g/24 
hours or requires 
outpatient IV 
hydration 
ER visit or 
hospitalization 
Headache 
No interference 
with activity 
Repeated use of 
non-narcotic pain 
reliever >24 hours 
or some 
interference with 
activity 
Significant; any 
use of narcotic pain 
reliever or prevents 
daily activity 
ER visit or 
hospitalization 
Fatigue 
No interference 
with activity 
Some interference 
with activity 
Significant; 
prevents daily 
activity 
ER visit or 
hospitalization 
Myalgia 
No interference 
with activity 
Some interference 
with activity 
Significant; 
prevents daily 
activity 
ER visit or 
hospitalization 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 78 of 80 
Systemic Illness 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Illness or clinical 
adverse event (as 
defined according 
to applicable 
regulations) 
No interference 
with activity 
Some interference 
with activity 
Prevents daily 
activity and 
requires medical 
intervention 
ER visit or 
hospitalization 
Serum* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4)** 
Sodium – Hyponatremia mEq/L 
132 – 134 
130 – 131 
125 – 129 
<125 
Sodium – Hypernatremia mEq/L 
144 – 145 
146 – 147 
148 – 150 
>150
Potassium – Hyperkalemia mEq/L 
5.1 – 5.2 
5.3 – 5.4 
5.5 – 5.6 
>5.6
Potassium – Hypokalemia mEq/L 
3.5 – 3.6 
3.3 – 3.4 
3.1 – 3.2 
<3.1 
Glucose – Hypoglycemia mg/dL 
65 – 69 
55 – 64 
45 – 54 
<45 
Glucose – Hyperglycemia 
Fasting – mg/dL 
Random – mg/dL 
100 – 110 
110 – 125 
111 – 125 
126 – 200 
>125
>200
Insulin requirements 
or hyperosmolar 
coma 
Blood Urea Nitrogen BUN mg/dL 
23 – 26 
27 – 31 
>31
Requires dialysis 
Creatinine – mg/dL 
1.5 – 1.7 
1.8 – 2.0 
2.1 – 2.5 
>2.5 or requires
dialysis
Calcium – hypocalcemia mg/dL 
8.0 – 8.4 
7.5 – 7.9 
7.0 – 7.4 
<7.0 
Calcium – hypercalcemia mg/dL 
10.5 – 11.0 
11.1 – 11.5 
11.6 – 12.0 
>12.0
Magnesium – hypomagnesemia mg/dL 
1.3 – 1.5 
1.1 – 1.2 
0.9 – 1.0 
<0.9 
Phosphorous – hypophosphatemia mg/dL 
2.3 – 2.5 
2.0 – 2.2 
1.6 – 1.9 
<1.6 
CPK – mg/dL 
1.25 – 1.5 x 
ULN*** 
1.6 – 3.0 
ULN 
3.1 – 10 x 
ULN 
>10 x ULN
Albumin – Hypoalbuminemia g/dL 
2.8 – 3.1 
2.5 – 2.7 
<2.5 
-- 
Total Protein – Hypoproteinemia g/dL 
5.5 – 6.0 
5.0 – 5.4 
<5.0 
-- 
Alkaline phosphate – increase by factor 
1.1 – 2.0 x 
ULN 
2.1 – 3.0 x 
ULN 
3.1 – 10 x 
ULN 
>10 x ULN
Liver Function Tests – ALT, AST 
increase by factor 
1.1 – 2.5 x 
ULN 
2.6 - 5.0 x 
ULN 
5.1 – 10 x 
ULN 
>10 x ULN
Bilirubin – when accompanied by any 
increase in Liver Function Test increase 
by factor 
1.1 – 1.25 x 
ULN 
1.26 – 1.5 x 
ULN 
1.51 – 1.75 
x ULN 
>1.75 x ULN
Bilirubin – when Liver Function Test is 
normal; increase by factor 
1.1 – 1.5 x 
ULN 
1.6 – 2.0 x 
ULN 
2.0 – 3.0 x 
ULN 
>3.0 x ULN
Cholesterol 
201 – 210 
211 – 225 
>226
-- 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 79 of 80 
Serum* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4)** 
Pancreatic enzymes – amylase, lipase 
1.1 – 1.5 x 
ULN 
1.6 – 2.0 x 
ULN 
2.1 – 5.0 x 
ULN 
>5.0 x ULN
*The laboratory values provided in the tables serve as guidelines and are dependent upon institutional normal
parameters. Institutional normal reference ranges should be provided to demonstrate that they are
appropriate.
** The clinical signs or symptoms associated with laboratory abnormalities might result in characterization
of the laboratory abnormalities as Potentially Life Threatening (Grade 4). For example. a low sodium value
that falls within a grade 3 parameter (125-129 mE/L) should be recorded as a grade 4 hyponatremia event if
the participant had a new seizure associated with the low sodium value.
***”ULN” is the upper limit of the normal range.
Hematology* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Hemoglobin (Female) - gm/dL 
11.0 – 12.0 
9.5 – 10.9 
8.0 – 9.4 
<8.0 
Hemoglobin (Female) 
change from baseline value - 
gm/dL 
Any decrease 
– 1.5
1.6 – 2.0 
2.1 – 5.0 
>5.0
Hemoglobin (Male) - gm/dL 
12.5 – 13.5 
10.5 – 12.4 
8.5 – 10.4 
<8.5 
Hemoglobin (Male) 
change from baseline value – 
gm/dL 
Any decrease 
– 1.5
1.6 – 2.0 
2.1 – 5.0 
>5.0
WBC Increase - cell/mm3 
10,800 – 
15,000 
15,001 – 
20,000 
20,001 – 
25,000 
>25,000
WBC Decrease - cell/mm3 
2,500 – 3,500 
1,500 – 2,499 
1,000 – 1,499 
<1,000 
Lymphocytes Decrease - cell/mm3 
750 – 1,000 
500 – 749 
250 – 499 
<250 
Neutrophils Decrease - cell/mm3 
1,500 – 2,000 
1,000 – 1,499 
500 – 999 
<500 
Eosinophils - cell/mm3 
650 – 1,500 
1,501 – 5,000 
>5,000
Hypereosinophilic 
Platelets Decreased - cell/mm3 
125,000 – 
140,000 
100,000 – 
124,000 
25,000 – 
99,000 
<25,000 
PT – increase by factor 
(prothrombin time) 
1.0 – 1.10 x 
ULN** 
1.11 – 1.20 x 
ULN 
1.21 – 1.25 x 
ULN 
>1.25 ULN
PTT – increase by factor 
(partial thromboplastin time) 
1.0 – 1.2 x 
ULN 
1.21 – 1.4 x 
ULN 
1.41 – 1.5 x 
ULN 
>1.5 x ULN
Fibrinogen increase - mg/dL 
400 – 500 
501 – 600 
>600
-- 
Fibrinogen decrease - mg/dL 
150 – 200 
125 – 149 
100 – 124 
<100 or 
associated with 
gross bleeding or 
disseminated 

PXVX0317 Vaccine 
EBSI-CV-317-004, Version 5.0 20 Mar 2023 
Emergent BioSolutions 
Confidential and Proprietary 
Page 80 of 80 
Hematology* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
intravascular 
coagulation (DIC) 
* The laboratory values provided in the tables serve as guidelines and are dependent upon institutional
normal parameters. Institutional normal reference ranges should be provided to demonstrate that they are
appropriate.
**“ULN” is the upper limit of the normal range.
Urine* 
Mild 
(Grade 1) 
Moderate 
(Grade 2) 
Severe 
(Grade 3) 
Potentially Life 
Threatening 
(Grade 4) 
Protein 
Trace 
1+ 
2+ 
Hospitalization or 
dialysis 
Glucose 
Trace 
1+ 
2+ 
Hospitalization 
for hyperglycemia 
Blood (microscopic) – red blood 
cells per high power field (rbc/hpf) 
1 – 10 
11 – 50 
>50 and/or
gross blood
Hospitalization or 
packed red blood 
cells (PRBC) 
transfusion 
* The laboratory values provided in the tables serve as guidelines and are dependent upon institutional
normal parameters. Institutional normal reference ranges should be provided to demonstrate that they are
appropriate.

Document Approvals
Approved Date: 20 Mar 2023
Document Approval Task
Verdict:  Approve
 Scientist, Clinical Research
Document Approval Task
Verdict:  Approve
 Sr. Director, Clinical Development
Document Approval Task
Verdict:  Approve
Sr Director, Biostatistics & Data Sciences
Document Approval Task
Verdict:  Approve
 VP, Clinical Development