EMA’s safety committee (PRAC) has completed its review of Ixchiq (a live attenuated chikungunya vaccine), following reports of serious side effects.
The previous temporary restriction on vaccinating people aged 65 years and above, which was put in place during the review, will now be lifted.
However, the Committee concluded 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.
Serious side effects with the vaccine were reported mainly in people 65 years of age and older and in those with several underlying medical conditions. These side effects led to a worsening of the patients’ medical conditions or a deterioration in their general health, in some cases leading to hospitalisation and death.
Many of the serious side effects reported are similar to symptoms of chikungunya infection and include fever, malaise (feeling unwell), loss of appetite and confusion, which can lead to falls. Chikungunya-like symptoms are mostly mild, but some adults (about 2 people in 100) may develop more severe symptoms.
The Committee also reviewed cases of encephalitis (inflammation of the brain) with symptoms such as confusion, sleepiness, fever and headache. Cases of encephalitis are rare and the frequency with which they occur is not known.
While most serious side effects occurred in older people, Ixchiq is effective at triggering the production of antibodies against the chikungunya virus which may be of particular benefit for older people who are at increased risk of severe chikungunya infection.
The Committee therefore concluded that 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.
Healthcare professionals are reminded that Ixchiq must not be given to people whose immune system is weakened because of disease or medical treatment. People with a weakened immune system are at greater risk of having complications from vaccines containing live attenuated viruses such as Ixchiq.
The vaccine was already contraindicated in people with weakened immune systems, and the contraindication remains in place. The product information for Ixchiq will be updated with the latest recommendations following this review.
Ixchiq was authorised in the EU in June 2024. At the start of the review, around 36,000 doses of the vaccine had been used worldwide.
A direct healthcare professional communication (DHPC) will be sent to healthcare professionals prescribing or administering the medicine. The DHPC will also be published on a dedicated page on the EMA website.
Ixchiq is a vaccine used to help protect people 12 years of age and older against chikungunya disease. It contains a strain of the chikungunya virus that has been attenuated (weakened).
When a person is given Ixchiq, the immune system recognises the weakened virus as ‘foreign’ and makes antibodies against it. If the person later comes into contact with the chikungunya virus, the immune system will be able to fight off the virus more effectively and so help to protect the person against chikungunya.
Most people infected with the chikungunya virus develop symptoms within 3–7 days. The most common symptoms of acute disease are fever and joint pain. Other symptoms can include headache, muscle pain, joint swelling, or rash. Most patients recover within a week, but some develop joint pain for several months or longer, which can be disabling. A small proportion of patients may develop severe acute disease, which can lead to multiorgan failure and is most often observed in newborns exposed to the virus during childbirth and adults over 65 years old.
The review of Ixchiq was initiated on 5 May 2025 at the request of the European Commission under Article 20 of Regulation (EC) No 726/2004.
The review has been carried out by the Pharmacovigilance Risk Assessment Committee (PRAC), the committee responsible for the evaluation of safety issues for human medicines, which has made a set of recommendations.
The PRAC recommendations will now be sent to the Committee for Medicinal Products for Human Use (CHMP), responsible for questions concerning medicines for human use, which will adopt the Agency’s opinion. The final stage of the review procedure is the adoption by the European Commission of a legally binding decision applicable in all EU Member States.