In August, the US Food and Drug Administration (FDA) suspended the license of the Chikungunya vaccine Ixchiq (VLA1553), manufactured by Austrian company Valneva. Produced with a live, attenuated version of the virus, it had been approved in November 2023. The decision was based on concerns about the safety of the vaccine, which appears to cause symptoms similar to those of Chikungunya in vaccinated individuals. One person died from encephalitis directly attributable to the vaccine, and serious adverse effects involving symptoms similar to those of Chikungunya led to 21 hospitalizations and three deaths. In April 2025, the Brazilian Health Regulatory Agency (ANVISA) approved the use of Ixchiq for people under 65 following tests conducted by researchers from Valneva and the Butantan Institute. In a statement, Butantan reported that it “has been monitoring the assessments of US regulatory agencies.” The European Medicines Agency (EMA) approved the vaccine in May 2024. In May 2025, it issued a recommendation against administering the vaccine to elderly people with comorbidities. France has reported eight cases of serious adverse effects (FDA, August 25).
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