The European Medicines Agency’s (EMA’s) Pharmacovigilance Risk Assessment Committee (PRAC) has recommended updating the product information for the live attenuated chikungunya vaccine, Ixchiq (Valneva), to reflect recent evidence that aseptic meningitis may occur post-vaccination in healthy young adults.

While aseptic meningitis was already a known risk of the Ixchiq vaccine, most previously reported cases had occurred in people older than 65 years and those with multiple long-term medical conditions.

A safety signal review was initiated after a reported case of aseptic meningitis in a healthy young adult following vaccination with Ixchiq. The EMA raises a safety signal in response to new information that suggests a previously unacknowledged and potentially causal association, or a new aspect of a known association, between a medicine and an adverse event that warrants further investigation. Safety signals may be generated from spontaneous reports, clinical studies, or the scientific literature.

EMA Urges Careful Consideration of Risks and Benefits 

The vaccine was authorized throughout the EU in 2024. Last July, the EMA lifted its temporary restriction on the chikungunya vaccine in people older than 64 years, which was put in place in May 2025 following reports of serious side effects in this age group, including three deaths. When lifting the restriction, the committee said that the vaccine should only be used after careful consideration of risks and benefits and when there is significant risk of chikungunya infection.

Ixchiq is not recommended for people who are immunodeficient or immunosuppressed.

Serious Side Effects in Healthy Young Adults 

PRAC’s safety signal review recommended an update to the vaccine’s product information to reflect the most recent evidence that serious side effects, such as aseptic meningitis, have also been observed in healthy young adults. 

The FDA suspended Ixchiq’s approval in the US in August last year due to similar serious safety concerns, and the agency subsequently placed a clinical hold on Ixchiq’s investigational new drug application to halt its development program. 

The FDA said it had received reports of one death from encephalitis “directly attributable” to the vaccine and more than 20 hospitalizations and deaths that were “consistent with chikungunya-like illness.” In January this year the manufacturer voluntarily withdrew Ixchiq from the US market.

Unknown Frequency of Serious Effects 

PRAC said that aseptic meningitis, encephalopathy, encephalitis, and other disorders of the nervous system are already listed as known side effects in Ixchiq’s product information. However, the available data do not allow an estimate of the frequency of these effects.

Symptoms include confusion, sleepiness, fever, headache, seizures, and neck stiffness. The EMA reinforced that anyone developing these symptoms after receiving the vaccine should seek medical attention immediately.

PRAC said it is also carrying out an evaluation of Ixchiq in the context of a regular 6-monthly periodic safety update report assessment. This will assess whether the newly available safety information has an impact on the balance of benefits and risks of Ixchiq. This is due to report in June 2026.