Chikungunya Vaccine Ixchiq: Serious Adverse Events Reported in France
A novel chikungunya vaccine, Ixchiq, has been available in France since March 2025 for individuals exposed to the virus transmitted by the tiger mosquito. Recent reports from the National Agency for the Safety of Medicines and Health Products (ANSM) confirm cases of serious adverse events following vaccination, while the product remains available for specific populations.
The ANSM’s latest report indicates that 21 cases of serious adverse effects have been recorded in France since the vaccination campaign began, out of a total of 62 reported cases . The vaccine continues to be closely monitored to identify those at risk of these rare complications.
62 Adverse Effects, Including 21 Serious Cases
“Since the start of vaccination, 62 cases of adverse effects, including 21 serious cases, have been reported on French territory,” the ANSM stated. Between June 2 and August 31, 2025, 15 new cases of adverse reactions were reported, including three serious cases . Many of these new cases were late reports for vaccinations administered before April 28, 2025, particularly among residents of areas with active virus circulation.
The most common serious effects reported are symptoms similar to those experienced during severe chikungunya infections – high fever, intense joint pain, and severe fatigue – collectively termed “chikungunya-like” syndrome.
Neurological Risks: Encephalitis, Encephalopathy, and Aseptic Meningitis
Initial analyses by French pharmacovigilance identified a signal of neurological damage, including cases of encephalitis and encephalopathy, primarily in individuals over 65 with multiple chronic conditions. This data was shared with the European Medicines Agency (EMA), leading to the inclusion of these rare complications in the vaccine’s product information and package leaflet.
In early 2026, reports from outside Europe highlighted another potential risk: aseptic meningitis, an inflammation of the brain’s coverings without bacterial involvement. A case occurred in a young, healthy adult following vaccination. On March 12, 2026, the EMA’s Pharmacovigilance Risk Assessment Committee (PRAC) recommended specifying that these serious cases could also affect young patients without pre-existing health conditions.
Who is Affected by the Chikungunya Vaccine Contraindications?
In response to these safety signals, authorities implemented restrictions, particularly for vulnerable groups. In France, the vaccine was initially suspended for those over 65, a measure subsequently adopted by the European Union. While the EMA reauthorized Ixchiq in July 2025, citing a favorable benefit-risk balance, France maintains the contraindication for seniors pending further evaluation.
The vaccine is also not recommended for individuals with weakened immune systems, following a reported case in an immunocompromised patient. For adults at risk of chikungunya exposure, Ixchiq remains authorized, but under strict medical supervision .
The Ixchiq vaccine is manufactured by Valneva and is one of the few available options against chikungunya, a viral disease transmitted by the tiger mosquito, causing fever and joint pain .