FDA Revokes License for First Chikungunya Vaccine, Ixchiq, Due to Serious Safety Events

In a major reversal, the FDA’s Center for Biologics Evaluation and Research (CBER) has suspended the biologics license for Ixchiq (Valneva Austria GmbH), the first vaccine approved for chikungunya. This decision, made on August 22, 2025, comes after reports of serious adverse events (SAEs), including hospitalizations and at least three deaths, which raised significant concerns about the vaccine’s safety profile.

A Troubling History of Post-Marketing Safety

Ixchiq, a live attenuated vaccine (meaning it contains a weakened version of the virus), was initially approved in November 2023 under an accelerated pathway for adults 18 and older at high risk of exposure. However, its post-marketing performance revealed a worrying pattern.

Serious Complications: Over 20 SAEs were reported, with a particularly concerning case involving a death from encephalitis where the vaccine strain of the chikungunya virus was detected in the patient’s spinal fluid.
Targeted Pause: This led the FDA and CDC to temporarily halt the vaccine’s use in adults 60 and older on May 9, 2025, for further investigation.
Decision to Suspend: Although the temporary pause was lifted on August 6, with enhanced safety warnings added to the label, the FDA ultimately concluded that the risks outweighed the benefits. The agency determined that the confirmatory trials required under the accelerated approval pathway had not yet verified a strong enough clinical benefit to justify the continued safety concerns.

The data revealed a specific vulnerability in older adults, particularly those with underlying health conditions, who were more likely to experience severe outcomes.

The Role of Pharmacists and the Alternative Vaccine

Pharmacists and other healthcare professionals were previously urged to weigh the risks and benefits of Ixchiq carefully, especially for at-risk populations. They were also advised to report any suspected adverse events to the Vaccine Adverse Event Reporting System (VAERS).

The FDA’s decision on Ixchiq comes as a second, different type of chikungunya vaccine has been approved. VimKunya (Bavarian Nordic), a virus-like particle (VLP) vaccine, received FDA approval in February 2025 for individuals ages 12 and older. Unlike Ixchiq, which uses a live virus, VimKunya’s VLP technology may offer a safer profile for vulnerable populations. Clinical trial data showed that VimKunya demonstrated a strong immune response in 98% of recipients, highlighting a new and potentially safer option in the fight against chikungunya.