Canadian federal health officials have issued a warning for clinicians administering IXCHIQ chikungunya vaccine in older, frail adults with comorbidities.

“Healthcare professionals are advised to carefully weigh the potential risks and benefits when considering IXCHIQ vaccination in individuals 65 years of age and older [and] instruct vaccinated individuals to promptly seek medical attention if they experience symptoms suggestive of severe reactogenicity or severe chikungunya-like adverse reactions following vaccination,” noted the alert. 

The Canadian Product Monograph for IXCHIQ has been updated to reflect this safety information.

IXCHIQ is a live, attenuated vaccine. It contains a live, weakened version of the chikungunya virus and may cause symptoms like those of chikungunya infection, which can cause sudden fever and severe joint pain. 

The disease is transmitted by the Aedes aegypti and Aedes albopictus mosquitoes: the same species that spread dengue fever and Zika virus disease.

Complications of the IXCHIQ vaccine can include malaise and decreased appetite, exacerbation of pre-existing diseases, confusional state, encephalopathy, or encephalitis, leading to falls, hospitalization, and death, according to the alert.

Such reactions are more likely to emerge in patients aged 75 years and older and those at high risk of having an undiagnosed immunocompromised condition such as occult cancer or immunosenescence, according to Health Canada.

The warning expands on similar advice issued in December 2025 by Canada’s travel medicine advisory committee (CATMAT), which recommended against using the vaccine in adults aged 65 years or older who have underlying conditions. 

The initial advice was based on postmarketing safety reports showing serious adverse events associated with the vaccine in this patient population, including neurologic and cardiac complications. 

While the CATMAT advice was directed mainly at travel clinics, the new Health Canada is a broader warning for clinicians and the public. 

Similar concerns have already triggered action elsewhere. In August 2025, the FDA’s Center for Biologics Evaluation and Research suspended the vaccine’s license stating “the vaccine does not have benefits outweighing risks, under most plausible scenarios.” 

In July 2025, the European Medicines Agency lifted a temporary restriction on the vaccine among patients older than age 65 years, but with the caveat that “for people of all ages, the vaccine should only be given when there is a significant risk of chikungunya infection and after a careful consideration of the benefits and risks.” 

Kate Johnson is a Montreal-based freelance medical journalist who has been writing for more than 30 years about all areas of medicine.