This is a prospective, double-blinded, multicenter, randomized, pivotal Phase 3 study comprising 4,115 subjects aged 18 years and above randomized in a 3:1 ratio to the live-attenuated CHIKV vaccine candidate (VLA1553) or placebo. The final dose of lyophilized VLA1553 or placebo will be administered as a single intramuscular immunization. Subjects in this study will be stratified into two age strata of 18 to 64 years and 65 years of age or above.

The primary objective of the study is to evaluate the immunogenicity and safety of the final dose of VLA1553 28 days following the single immunization. Immunogenicity evaluations in the immunogenicity subset will include the proportion of subjects with seroprotective neutralizing CHIKV antibody titers above a surrogate threshold indicative of protection.

The surrogate of protection reasonably likely to predict clinical benefit has been established in non-human primate passive transfer studies using human sera from the Phase 1 study. Safety data collection and immunogenicity will continue to be assessed until Month 6

The first enrolled and randomized approximately 500 subjects will comprise the immunogenicity subset.

Results

On December 5, 2022, Valneva reported positive 12-month results for their single-shot  Chikungunya vaccine candidate.

There were no safety concerns identified in the 12-month follow-up, antibody levels were stable from month 6 to month 12, and the primary endpoint met with a 99% seroresponse rate.

Valneva announced on March 8, 2022, the successful completion of the Phase 3 pivotal trial of its single-shot chikungunya vaccine candidate, VLA1553.

The final analysis confirmed the very high level of seroprotection, with 98.9% of participants achieving protective levels of chikungunya virus (CHIKV) neutralizing antibodies one month after receiving a single vaccination (263 of 266 subjects from the per-protocol subgroup tested for immunogenicity, 95% CI: 96.7-99.8).

The positive final analysis included six-month follow-up data and confirmed the topline results reported in August 2021. Valneva now expects to commence the pre-submission process with the U.S. Food and Drug Administration (FDA) in the second quarter of 2022.