Long-term Follow-up Study to Evaluate Safety and Immunogenicity of PXVX0317 Single or Booster Vaccination

Inclusion Criteria

• •Only within the EBSI-CV-317-004 feeder study informed consent form (ICF) (and/or assent form, as applicable), the participant voluntarily signed and agreed to be contacted or did not indicate they were not to be contacted for potential screening and enrollment in a future study (ie, EBSI-CV-317-008).
• •Able and willing to provide informed consent (and assent, as applicable) voluntarily signed by participant (and guardian, as applicable) for participation in this rollover study EBSI-CV-317-008, including possible receipt of a booster dose of CHIKV VLP vaccine.
• •Males or females, 12 years of age or older at the time of enrollment in the feeder study.
• •Received a single dose of CHIKV VLP vaccine in one of the feeder studies, EBSI-CV-317-004 or EBSI-CV-317-005.
• •Demonstrated compliance to the feeder study conduct (ie, rollover participant was without protocol deviations that excluded them from immunogenicity analysis in feeder study EBSI-CV-317-004 or EBSI-CV-317-005) without discontinuation or early withdrawal.
• •Generally healthy, in the opinion of the investigator, based on medical history and physical examination.
• •\- Women who are either: i. Not of childbearing potential (CBP): premenarche, surgically sterile (at least six weeks postbilateral tubal ligation or bilateral total salpingectomy, 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). For women who are postmenopausal, documented follicle stimulating hormone (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. or: ii. Meet all the below criteria:
• •Negative serum pregnancy test at Prerandomization and Prebooster Visits
• •Negative urine pregnancy test immediately prior to booster dose administration
• •Use one of these acceptable methods of contraception (if women of CBP) for at least six months after booster:
• •Hormonal contraceptives (eg, implants, pills, patches) initiated ≥30 days prior to booster dose administration
• •Intrauterine device (IUD) inserted ≥30 days prior to booster dose administration
• •Double barrier type of birth control (male condom with female diaphragm, male condom with cervical cap)
• •Abstinence is acceptable only for adolescents (12-\<18 years of age) who are not sexually active.
• •Women participants of CBP must use an acceptable method of contraception from ≥30 days prior to Randomization A or assignment to Group 1; those who are randomized to Groups 2 or 3 at year 3 can discontinue contraception until 30 days prior to booster dose administration, if desired. Women participants of CBP must use an acceptable method of contraception from ≥30 days prior to Randomization B through six-months postbooster vaccination dose (if applicable).
• •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 during the same time period as women of CBP are required to use contraception. Contraception requirements do not apply to Group 4 participants (unrandomized or unboosted).