A Seamless Phase II/III, Observer-blind, Multi-centre, Randomized Clinical Trial to Evaluate Immunogenicity and Safety of BBV87, an Inactivated Chikungunya Virus Vaccine in Healthy Subjects 12-65 Years of Age

The current study is designed to evaluate the safety, immunogenicity, and lot-to-lot consistency of the BBV87 40 μg vaccine in healthy subjects.This Phase III study is a randomized, observer blind, placebo-controlled, multi-centre, lot-to-lot consistency study with a two-dose schedule. Approximately, 1000 healthy subjects 12 to 65 years of age will be randomized irrespective of CHIKV serological status at Visit 1. Nine hundred subjects will be randomized equally among three lots of BBV87 40 μg. (Lot A, Lot B,and Lot C) while 100 subjects will be administered a placebo. Thus, approximately 1000 subjects will be randomized in allocation ratio 3:3:3:1 (BBV87 40 μg. Lot A: BBV87 40 μg. Lot B: BBV87 40 μg. Lot C: Placebo). Subjects will receive 40 μg dose strength of BBV87, based on the dose approved by the DSMB and CDSCO in the Phase II study. After Day 56, the DSMB will review the safety data during the study to safeguard the interests of trial subjects and assess the vaccine's safety.

Inclusion Criteria: 1. Healthy male and female subjects aged between 12 to 65 years (both inclusive).

2. Subject or Subject's Parent should be willing to give voluntary written informed consent and/or assent prior to inclusion in the study.

3. Must be able to comprehend and comply with study requirements and procedures and be able and willing to complete subject diary.

4. Willing to consent to the storage and future use of biological samples for CHIKV related research.

5. Male subjects who are sexually active or married and female subjects who are sexually active or married and are of child-bearing potential should be willing to follow effective birth control* methods for at least 3 months after the last dose of vaccine.

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Exclusion Criteria: 1. History of rheumatoid arthritis and moderate or severe arthritis or arthralgia within past 90 days prior to Visit 1.

2. Subject a known case of diabetes mellitus (Type 1 and 2). 3. History of degenerative neurological disease (e.g. Guillain Barre Syndrome, Multiple Sclerosis).

4. Any clinically significant laboratory values or illness or any other current or pre-existing health condition (e.g. any major pulmonary, cardiovascular, renal, neurological, metabolic, gastro-intestinal, hepato-biliary, haematological functional abnormality, mental or physical disability, blood dyscrasia, major congenital defects, etc.) which in the opinion of the Investigator may affect the safety of the subject or the study endpoints.

5. History of allergic/hypersensitivity reactions or anaphylaxis to any vaccine or components of study vaccine.

6. Subject has any acute illness (moderate or severe) at the time of vaccination and/or fever (oral temperature ≥ 38°C or ≥ 100.4 °F) within 48 hours prior to vaccination.

7. Subject has history of cancer, organ transplant, any other clinically significant immunosuppressive condition or autoimmune disease (e.g. Systemic Lupus Erythematosus, autoimmune thyroid disease). 8. Subjects who are pregnant or breastfeeding. 9. Prior major surgery or radiation therapy within 4 weeks of Visit 1. 10. Known or suspected cases of HIV and Hepatitis B surface antigen (HBsAg); or any potentially communicable infectious disease as determined by the Investigator.

11. Current (within 14 days before Visit 1) or anticipated concomitant immune-modifying or immunosuppressive therapy (excluding inhaled, topical skin, or eye drop-containing corticosteroids, low-dose methotrexate, or corticosteroids at a dose less than 20 mg/day).

12. Administration of blood or blood product derivatives or any immunoglobulin preparation, 90 days before Visit 1.

13. Active addictive drug or alcohol use or dependence that, in the opinion of the Investigator, would interfere with adherence to study requirements or assessment of immunologic endpoints.

14. Participating in a clinical trial of any vaccine, including CHIKV, within 30 days before Visit 1 or planning to participate during the study.

15. Any other condition which in the opinion of the Investigator may affect subject's safety or participation.

The appearance of the placebo is slightly different from that of the investigational vaccine. The storage temperature of BBV87 40 μg is +2º to +8°C, and that of the placebo (normal saline) is room temperature. Therefore, this study was designed as an observer-blind study where subjects, the Investigator, the study team from the Sponsor/Designee, and the study personnel responsible for evaluating the study outcomes will be unaware of the study vaccine administered. The clinical laboratories analysing the blood samples for immunogenicity will also be blinded to the treatment assignment.The study vaccine will be dispensed by designated unblinded personnel who will not participate in any clinical study evaluations. Additionally, there will be a few unblinded Sponsor/Designee personnel, including an unblinded statistician, who will be responsible for generating an unblinded report if requested by the DSMB members, unblinded personnel responsible for incorporating the randomization sheets