FDA Suspends Valneva’s Ixchiq Chikungunya Vaccine Over Safety Risks

French drugmaker Valneva (Nasdaq: VALN) has seen a dramatic reversal for its chikungunya vaccine Ixchiq. Within two weeks, the vaccine went from partial clearance to a full suspension. On August 22, the U.S. Food and Drug Administration (FDA) revoked Ixchiq’s license over severe safety concerns. Valneva’s shares plummeted more than 20% that day, marking its steepest fall since June 2022.

Ixchiq Safety Issues: Hospitalizations, Deaths, and Encephalitis

The FDA’s rare hardline stance followed new alerts from its Center for Biologics Evaluation and Research (CBER). Reports linked Ixchiq to over 20 serious adverse events. These included 21 hospitalizations and three deaths.

One death was directly attributed to “vaccine-derived encephalitis.” CBER noted the vaccine “appears to trigger chikungunya-like illness” in recipients.

CBER explained that updated risk-benefit analysis showed limited benefit. In most scenarios, vaccine risks outweighed its protection. The agency warned continued use could pose public health threats. Based on this assessment, the FDA concluded Ixchiq was unsafe and revoked authorization.

Valneva confirmed these cases mirrored clinical trial and post-market safety data, especially in older adults flagged in its product labeling.

From Accelerated Approval to Full FDA License Suspension

Ixchiq’s U.S. regulatory path has been turbulent. The live-attenuated vaccine received FDA’s accelerated approval in November 2023. It was intended to protect adults traveling to endemic regions.

By May 2025, post-market safety signals prompted FDA and CDC to recommend suspension in people over 60. Unexpectedly, the FDA lifted that restriction on August 8 after review. Markets assumed the concerns had eased.

Yet only two weeks later, new adverse events pushed FDA to escalate action. The agency moved from partial suspension to full license revocation.

Reuters highlighted another factor: Ixchiq’s confirmatory trial has yet to show clear clinical benefit. This gap may have reinforced FDA’s decision when confronted with new safety data.

Bavarian Nordic Now Dominates U.S. Chikungunya Vaccine Market

Following the FDA ban, Valneva announced on August 25 it had halted all Ixchiq shipments and sales in the U.S. The vaccine generated €7.5 million ($8.78 million) in first-half 2025 sales, about 8% of product revenue. The company said it may permanently exit the U.S. market but kept its annual financial forecast unchanged.

Ixchiq’s withdrawal reshapes the chikungunya vaccine landscape in the U.S. The only remaining option is Bavarian Nordic’s Vimkunya, approved in April 2025. Unlike Ixchiq, Vimkunya is cleared for use in individuals 12 years and older.

Author

Steven Chung

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