U.S. health authorities are now advising older Americans to avoid the chikungunya vaccine. The warning follows reports of life-threatening complications, including two deaths, in recently vaccinated seniors.
The Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) issued a safety notice on May 9, warning adults aged 60 and older to hold off on receiving Ixchiq, the only FDA-approved chikungunya vaccine in the United States.
The vaccine was originally greenlit in November 2023 for use in adults 18 and older who plan to travel to areas where the mosquito-borne virus is common.
Chikungunya is a painful tropical illness spread by mosquito bites, marked by sudden fever and joint pain. The CDC reports 100 to 200 cases annually among U.S. travelers returning from regions with outbreaks.
In approving Ixchiq, federal regulators had declared the virus an “emerging global health threat” with more than five million cases recorded globally over the past 15 years.
However, the vaccine, developed by French biotech firm Valneva, uses a live, weakened form of the virus. That design may have contributed to serious complications in older recipients, including neurologic and cardiac events.
Two individuals, aged 62 and 79, died shortly after vaccination. One reportedly suffered encephalitis, or inflammation of the brain.
In total, U.S. officials are reviewing 17 cases of adverse events, all involving patients between 62 and 89 years old. Six of those cases were discussed last month in a CDC advisory panel meeting, where experts flagged issues like heart problems and brain inflammation that occurred within days of vaccination. Most of the affected patients had preexisting health conditions.
European regulators are conducting a parallel investigation. In the meantime, U.S. officials say they will continue evaluating safety reports and conduct a full benefit-risk assessment before updating guidance.
The CDC has not revoked its recommendation for younger travelers to receive the vaccine, but the agencies made it clear that those over 60 should wait.
In light of the concerns, a CDC advisory committee has also proposed the availability of a second chikungunya vaccine, Bavarian Nordic’s Vimkunya, which would be open to travelers aged 12 and up. A final decision on that recommendation is still pending.
For now, older Americans planning international travel are urged to consult with their doctors, particularly if they are heading to regions known for chikungunya outbreaks. The FDA and CDC pledged to provide further updates once their safety review is complete.