The Directorate of Health
EMA Launches Review of Chickenpox Vaccine Following Reported Encephalitis Case
6th June 2025
The European Medicines Agency’s Pharmacovigilance Risk Assessment Committee (PRAC) has initiated a safety review of chickenpox vaccines following a fatal case of encephalitis in Poland after vaccination with Varilrix.
The review follows a report describing a child who developed encephalitis - an inflammation of the brain - shortly after receiving the Varilrix vaccine and later died. As a precaution, Polish health authorities have suspended use of the specific Varilrix batch involved. That batch has not been distributed in Iceland.
PRAC’s investigation will include a comprehensive analysis of all available data, including any similar cases and reports associated with Varivax, another chickenpox vaccine from a different manufacturer. Both Varilrix and Varivax are currently available in Iceland, with one integrated into the national immunisation schedule since 2020 and the other offered to children and adults outside of it.
Chickenpox vaccines contain a live, attenuated (weakened) form of the varicella-zoster virus, which has been used globally for more than 30 years. The virus itself can cause encephalitis and other neurological problems, as it can persist permanently in nerve tissue following a chickenpox infection.
After initial infection, the virus can remain dormant in the body and later reactivate as shingles (herpes zoster), typically affecting the nerves and skin. Emerging research suggests that shingles vaccination might also lower the risk of dementia, hinting at a potential link between varicella-zoster virus and neurodegenerative conditions.
While rare, encephalitis cases have been reported in connection with chickenpox vaccination. In most instances, a direct link has not been established. Notably, confirmed cases often involved immunocompromised individuals, such as those recently treated with high-dose steroids. Healthcare providers are advised to evaluate such patients carefully before administering live vaccines.
In Iceland, only one serious adverse reaction - a hemorrhagic/ischemic stroke - has been reported following Varilrix vaccination, occurring five months after administration, leaving causality uncertain.
As the PRAC’s review continues, no changes have been made to the current vaccination guidelines. Healthy children and adults without prior chickenpox infection are still encouraged to be vaccinated. However, individuals who are immunocompromised, recently treated with high-dose steroids, undergoing immunoglobulin therapy, or taking salicylate medications (e.g., aspirin, Pentasa, or Salazopyrin) should consult with a healthcare provider before vaccination, including regarding the timing of vaccination and concurrent medication use.
Sources:
The Chief Epidemiologist