The U.S. Food and Drug Administration (FDA) announced on August 25, 2025, the suspension of approval for Ixchiq, a vaccine developed by France-based Valneva to combat chikungunya, a mosquito-borne virus causing fever, severe joint pain, and inflammation.
The decision stems from mounting reports of serious adverse events (SAEs), prompting regulators to conclude that the vaccine’s risks now outweigh its benefits and pose a danger to public health.
Ixchiq, a live-virus vaccine, received accelerated FDA approval in November 2023 for adults 18 and older at heightened risk of chikungunya exposure. The Centres for Disease Control and Prevention (CDC) endorsed it in 2024 for travellers to affected regions.
However, concerns emerged earlier this year.
In May, health officials recommended pausing vaccinations for elderly adults after 38 SAE reports involving 32 unique cases—seven in the U.S. and 25 abroad—including neurologic and cardiac issues, 21 hospitalisations, and three deaths.
Following the resignation of CBER Director Dr. Vinay Prasad, the FDA briefly lifted the pause in early August, citing an updated risk-benefit assessment favouring the vaccine for certain groups. But new data reversed that stance. Four additional foreign reports surfaced, including one involving a 55-year-old male.
Of the 32 cases, five tested positive for the vaccine strain, with one death from encephalitis directly linked via cerebrospinal fluid PCR testing. Prasad’s August 22 memorandum emphasised that these incidents make it ”nearly certain” the vaccine caused the problems, and clinical benefits remain unverified without confirmatory studies.
Valneva described the suspension as ”sudden” and maintains commitment to the vaccine amid escalating global chikungunya threats. CEO Thomas Lingelbach stated the company is investigating cases, noting SAEs align with clinical trial data and label warnings for potential ”serious, severe, or prolonged chikungunya-like illness.” Valneva may pursue statutory appeals.