US suspends chikungunya vaccine after reports of severe side effects

Ixchiq is one of only two vaccines approved by the FDA for chikungunya, a mosquito-borne virus that mainly occurs in tropical and subtropical regions but has recently spread to countries worldwide.
The United States has suspended the license for the Ixchiq vaccine against the chikungunya virus following reports of serious adverse effects.
In a statement on Monday, Valneva, the French company that developed Ixchiq, said the US Food and Drug Administration (FDA)issued the suspension on Friday after four additional cases of severe side effects, three of which involved people aged 70 to 82.
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“The suspension of the licence is effective immediately,” Valneva said.
Ixchiq is one of only two vaccines approved by the FDA for chikungunya, a mosquito-borne virus that mainly occurs in tropical and subtropical regions but has recently spread to countries worldwide.
Valneva obtained US approval for the vaccine in 2023, but reports of adverse events prompted regulatory reviews, particularly for older patients, including by the European Medicines Agency earlier this year.
“As we determine potential next steps, and as the clear threat of chikungunya continues to escalate globally, Valneva remains fully committed to maintaining access to our vaccine as a global health tool for addressing and preventing outbreaks of this devastating illness,” Valneva’s chief executive, Thomas Lingelbach, said.
“We aim to continue providing Ixchiq to all countries where the product is licensed and continue our efforts with our partners to accelerate vaccine access in low-and-middle-income chikungunya-endemic countries, especially in response to any current or future chikungunya outbreaks, ensuring the vaccine reaches those most in need.”
The company added that it is evaluating the financial impact of the suspension but is not modifying its revenue guidance. Ixchiq generated 7.5 million euros ($8.8 million) in sales in the first half of 2025. However, the announcement has led to a more than 26 per cent drop in Valneva’s shares on the Paris stock exchange.
The FDA’s decision follows updated data from the Vaccine Adverse Event Reporting System, including cases outside the United States. Of the four new cases, three involved individuals aged 70 to 82, including one 82-year-old who was hospitalised for two days and later discharged. The remaining case involved a 55-year-old.
Valneva noted that all cases describe symptoms consistent with those previously reported in clinical trials and post-marketing experience, particularly among elderly individuals.
Chikungunya virus is transmitted by Aedes mosquitoes and causes fever, severe joint and muscle pain, headache, nausea, fatigue, and rash. While rarely fatal, the virus can be dangerous for infants and the elderly. Public health experts have warned that the disease could become a future pandemic threat as climate change expands mosquito habitats.
In July, the World Health Organisation highlighted the risk of a major chikungunya epidemic, citing early warning signs similar to a 2004 outbreak in the Indian Ocean region that eventually affected nearly half a million people. This year, Europe has already recorded 27 chikungunya outbreaks, a new continental record, according to the European Centre for Disease Prevention and Control.
Kenya has also reported cases of chikungunya, with outbreaks confirmed in Mombasa County, where the Kenya Medical Research Institute (KEMRI) said 25 of 45 suspected cases tested positive.
Valneva said it continues to investigate the reported cases in detail and will take further steps in consultation with health authorities. The company also reaffirmed its commitment to safety standards and global vaccine access.
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