Stephen I. Feller , 2025-05-13 21:02:00
Key takeaways:
- The world’s first chikungunya vaccine has been associated with 17 serious adverse events and two deaths.
- U.S health officials recommended pausing vaccination among adults aged 60 years and older.
The CDC and FDA this week recommended that clinicians stop giving people aged 60 years or older the world’s first chikungunya vaccine while they investigate adverse health events associated with the shot.
The vaccine “contains a live, weakened version of the chikungunya virus and may cause symptoms similar to those of chikungunya disease,” the U.S. health agencies said in a joint press release. “Some of the post-marketing reports include adverse events that are consistent with severe complications of chikungunya disease, resulting in hospitalization.”
Data derived from FDA and CDC.
The recommendation is based on reports of 17 serious adverse events globally, including two deaths, among people aged 62 to 89 years who received the vaccine.
The European Medicines Agency (EMA) is also reviewing the use of the vaccine among adults aged 65 years or older and has temporarily restricted giving the vaccine to people in that age group.
Among the 17 reports of adverse events, the FDA and CDC said six came from the U.S.
According to the EMA, both fatal cases occurred on Reunion Island, a French department in the Indian Ocean — one in a man aged 84 years who developed encephalitis and the other in a man aged 77 years with Parkinson’s disease whose difficulty swallowing may have caused aspiration pneumonia.
A vaccination campaign on the island prioritized people aged 65 years or older with comorbidities until April 25, when France’s national public health agency suspended its recommendation for the vaccine, called Ixchiq, for that age group so it could investigate the two deaths, according to Valneva, which manufactures the vaccine. The campaign continues for people aged 12 to 64 years.
The EMA said that, in addition to people aged 65 years or older, the vaccine should also not be given to anybody with a weakened immune system due to disease or medical treatment.
“Persons with a weakened immune system are at greater risk of having complications from vaccines containing live attenuated viruses, regardless of age,” EMA officials said.
The FDA approved the vaccine in November 2023 for people aged 18 years or older who are at high risk for exposure to the virus, which is spread by bites from infected Aedes mosquitoes. Because the approval came under an accelerated approval process, the FDA also required a phase 4 post-marketing safety study.
The EMA approved the vaccine in June 2024, making it available in Austria, Belgium, Denmark, Finland, France, Germany, Luxembourg, the Netherlands, Norway and Sweden.
Upwards of 80,000 doses of the vaccine have been distributed globally, the FDA said, with a little more than 43,000 people so far receiving shots, according to the EMA.
The FDA approval was based on two clinical trials in North America with roughly 3,500 participants aged 18 years or older, one of which included testing the vaccine against a placebo, the agency said.
According to the agency, severe chikungunya-like adverse reactions occurred in 1.6% of vaccine recipients during the two studies. Some recipients also experienced adverse reactions for at least 30 days, and two of them were hospitalized with severe adverse reactions.
Valneva chief medical officer Juan Carlos Jaramillo, MD, said in a press release that the company continues to see a positive risk-benefit of the vaccine to most people at greater risk for chikungunya exposure, noting that the CDC, FDA and EMA have, for the most part, retained their recommendations for other age groups.
“We will continue engaging proactively with the global regulatory authorities while these important investigations continue over the coming months,” Jaramillo said.
References:
- CDC. Chikungunya virus: Chikungunya vaccine information for healthcare providers. https://www.cdc.gov/chikungunya/hcp/vaccine/index.html. Updated May 10, 2025. Accessed May 13, 2025.
- EMA. Ixchiq: Chikungunya vaccine (live). https://www.ema.europa.eu/en/medicines/human/EPAR/ixchiq#authorisation-details. Last updated April 9, 2025. Accessed May 13, 2025.
- EMA starts review of Ixchiq (live attenuated chikungunya vaccine). https://www.ema.europa.eu/en/news/ema-starts-review-ixchiq-live-attenuated-chikungunya-vaccine. Published May 7, 2025. Accessed May 13, 2025.
- FDA and CDC recommend pause in use of Ixchiq (chikungunya vaccine, live) in individuals 60 years of age and older while postmarketing safety reports are investigated. https://www.fda.gov/vaccines-blood-biologics/safety-availability-biologics/fda-and-cdc-recommend-pause-use-ixchiq-chikungunya-vaccine-live-individuals-60-years-age-and-older. Published May 9, 2025. Accessed May 13, 2025.
- Valneva provides update following European Medicines Agency announcement on use of Ixchiq in elderly. https://valneva.com/press-release/valneva-provides-update-following-european-medicines-agency-announcement-on-use-of-ixchiqin-elderly/. Published May 7, 2025. Accessed May 13, 2025.
- Valneva provides update on recommended use of Ixchiq by elderly individuals in the United States. https://valneva.com/press-release/valneva-provides-update-on-recommended-use-of-ixchiq-by-elderly-individuals-in-the-united-states/. Published May 12, 2025. Accessed May 13, 2025.
Perspective
This pause parallels another live arboviral vaccine, yellow fever, where there is a precaution for people aged 60 years or older. No other live-attenuated vaccines are currently in routine use in this age cohort in the United States. Immunosenescence affects older persons’ ability to adequately control replication of all live attenuated vaccine viruses.
A concern of some experts is that the younger, healthier persons are also getting some systemic vaccine-induced viral inflammation in the CNS and/or joints but are young enough to escape encephalopathy. FDA and CDC caution is certainly merited given the approval in February 2025 of an effective non-live chikungunya vaccine (Vimkunya, Bavarian Nordic) which is very well tolerated.
Many travel medicine experts I have spoken to would recommend avoidance of a live viral chikungunya vaccine in any age group until all these severe adverse events are worked out. This is not like yellow fever vaccines where there is no choice — the Advisory Committee on Immunization Practices voted on April 16 to recommend Vimkunya to all groups aged 12 years or older. [Editor’s note: The CDC has not yet signed off on this recommendation.]
David O. Freedman, MD, FIDSA
Professor of infectious diseases
University of Alabama at Birmingham
Disclosures: Freedman reports no relevant financial disclosures.
