The European Medicines Agency's Pharmacovigilance Risk Assessment Committee (PRAC) has launched a comprehensive review of two widely-used chickenpox vaccines following a fatal case of encephalitis in a Polish child who received the Varilrix vaccine.
The investigation was triggered by a case report from Poland describing a child who developed encephalitis—inflammation of the brain—within days of receiving the Varilrix vaccine and subsequently died from complications. As a precautionary response, Polish health authorities have suspended distribution of the specific vaccine batch involved in the incident.
Vaccine Safety Profile Under Scrutiny
Both Varilrix and Varivax are licensed for vaccination against chickenpox in adults and children aged 12 months and older, with some populations eligible from 9 months of age. The vaccines contain live attenuated varicella-zoster virus and have been used globally for more than 30 years.
Encephalitis is already listed as a side effect in the product information for both vaccines, based on rare reports during post-marketing surveillance. However, the PRAC will now evaluate all available evidence to better understand the risk profile and determine whether additional regulatory measures are necessary.
Clinical Context and Risk Factors
Chickenpox primarily affects children between ages 2 and 8, where it typically presents as a mild, self-resolving condition. However, complications can occur, including bacterial skin or blood infections, pneumonia, and encephalitis. The varicella-zoster virus itself can cause encephalitis and other neurological problems, as it persists permanently in nerve tissue following infection.
Healthcare providers have been advised to exercise particular caution with immunocompromised patients. Confirmed encephalitis cases following vaccination often involve individuals with compromised immune systems, such as those recently treated with high-dose steroids. Patients who are immunocompromised, undergoing immunoglobulin therapy, or taking salicylate medications should consult healthcare providers before vaccination.
Regulatory Response and Current Guidelines
While the investigation continues, no changes have been made to current vaccination guidelines. The vaccines remain available for use throughout the European Union in accordance with approved product information. Healthy children and adults without prior chickenpox infection are still encouraged to receive vaccination.
In Iceland, where both vaccines are available—one integrated into the national immunization schedule since 2020—only one serious adverse reaction has been reported following Varilrix vaccination: a hemorrhagic/ischemic stroke occurring five months after administration, with uncertain causality.
The PRAC's review will include comprehensive analysis of all available data, including similar cases and reports associated with both Varilrix and Varivax. The committee aims to provide clarity on the risk-benefit profile of these vaccines while ensuring continued protection against chickenpox complications in the broader population.
