On Aug. 25, 2025, shares of French drugmaker Valneva slumped more than 20% after the U.S. Food and Drug Administration (FDA) suspended the license for its chikungunya vaccine, Ixchiq, with immediate effect, citing serious safety concerns.

The FDA’s Center for Biologics Evaluation and Research (CBER) said the suspension was based on reports of more than 20 serious adverse events, including 21 hospitalizations and three deaths, with one fatality directly linked to vaccine-derived encephalitis.

The regulator noted that while Ixchiq received accelerated approval in November 2023 for adults at increased risk of chikungunya, confirmatory trials have yet to demonstrate clear clinical benefit.

Valneva said it would immediately halt shipping and sales of the vaccine in the United States. The company is also evaluating the potential impact of permanently withdrawing the vaccine from the U.S. but would not change its financial outlook. With the FDA suspending Ixchiq’s license, Bavarian Nordic’s Vimkunya is the sole remaining chikungunya vaccine available in U.S.

Ixchiq, which was also approved in Europe, uses a weakened form of the virus to stimulate an immune response.