Chikungunya Virus VLP Vaccine: Phase 3 Trial in Adolescents and Adults

1BackgroundChikungunya disease is a growing global public health concern. Chikungunya virus (CHIKV) virus-like particle (VLP) vaccine is a single dose, pre-filled syringe for intramuscular injection. MethodsA pivotal phase 3 randomized, double-blind, placebo-controlled trial was conducted in healthy adolescents and adults 12-64 years of age. Participants received either CHIKV VLP vaccine or placebo on Day 1. Immunogenicity objectives assessed CHIKV serum neutralizing antibody (SNA) titers (NT80) at selected timepoints. Safety was assessed through Day 183 postvaccination. ResultsA total of 2790 participants received CHIKV VLP vaccine and 464 received placebo (n=3454). Coprimary endpoints were met including 1) immunologic superiority to placebo and 2) geometric mean titer at Day 22. Results demonstrated that CHIKV VLP vaccine induced a protective seroresponse (SNA NT80 [≥]100; considered the presumptive seroprotective antibody response), in 97% of individuals at Day 15 (2 weeks), in 98% of individuals at Day 22, and in 86% of individuals at Day 183 (6 months). CHIKV VLP vaccine demonstrated a favorable safety profile. The majority of adverse events were self-limited and grade 1 or 2 in severity. The most common adverse events were injection site pain, fatigue, headache, and myalgia. ConclusionsCHIKV VLP vaccine induces a rapid and robust immune response by Day 15 that lasts through Day 183 postvaccination. These findings support the potential for this vaccine to protect individuals 12-64 years of age from disease caused by CHIKV. (Funded by Emergent BioSolutions Inc. and Bavarian Nordic A/S [as successor in interest to Emergent BioSolutions Inc.]; ClinicalTrials.gov number, NCT05072080).