Seventeen serious adverse events, including two deaths, have been reported in adults aged 62 to 89 following postmarketing use of the Ixchiq chikungunya vaccine.

The U.S. Food and Drug Administration (FDA) and Centers for Disease Control and Prevention (CDC) have recommended a pause in the use of Ixchiq (Chikungunya Vaccine, Live) in patients aged 60 years and older following postmarketing reports of serious adverse events, including neurologic and cardiac events. As of May 7, 2025, a total of 17 serious adverse events—two of which were fatal—have been reported globally in patients aged 62 to 89 years who received the vaccine. Six cases were reported in the U.S. Most affected patients had underlying chronic conditions.

Several reports described complications that were consistent with severe chikungunya disease, including hospitalization and one fatal case of encephalitis. Ixchiq’s prescribing information includes a warning regarding the potential for severe or prolonged chikungunya-like adverse reactions.

Although severe adverse events were infrequent in clinical trials, 1.6% of Ixchiq recipients experienced reactions that impaired daily activities or required medical care. Two patients required hospitalization, and some reported symptoms that persisted for 30 days or longer. No such events were reported among placebo recipients.

Ixchiq, which contains a live attenuated chikungunya virus, was approved by the FDA on November 9, 2023, for use in adults aged 18 years and older who were at increased risk of exposure to the chikungunya virus. Approximately 80,000 doses have been distributed globally.

An updated benefit-risk assessment is underway to evaluate the safety of Ixchiq in patients aged 60 years and older. The FDA and CDC will continue monitoring postmarketing safety data and will issue further guidance upon completion of the review.

Clinicians are encouraged to report adverse events through the Vaccine Adverse Event Reporting System, which is comanaged by the FDA and CDC.

Source: FDA