Developing a Chikungunya Virus Vaccine

Chikungunya (CHIK) virus causes periodic massive outbreaks of disease characterized by fever and arthritis, but licensed anti-CHIK therapeutics or vaccines are lacking. A live attenuated CHIK vaccine (VLA1553) has yielded encouraging safety and immunogenicity results in early phase human testing. Now, investigators randomized 4128 healthy adults 3:1 (55% female; median age, 45) to receive VLA1553 or placebo at multiple U.S. sites in a phase 3 clinical trial. The primary endpoint was the proportion of participants who achieve a 50% reduction in micro plaque reduction neutralization titer (µPRNT₅₀) of ≥150 at 28 days after vaccination.

Among 3093 participants in the VLA1553 group (compared with 1035 in the placebo group), a µPRNT₅₀ of ≥150 was…