Chickenpox Vaccine product Facts Updated Following Fatal Encephalitis Case
Amsterdam, NL – The European Medicines Agency’s (EMA) Pharmacovigilance Risk Assessment Committee (PRAC) has recommended an update to the product information for the varicella (chickenpox) vaccines Varilrix and Varivax. This change aims to provide more detailed information regarding the severity of the risk for encephalitis, a serious inflammation of the brain.
The recommendation follows a safety review initiated after a fatal case of encephalitis occurred in a child in Poland shortly after receiving Varilrix,a live-attenuated varicella vaccine. The updated product information will now explicitly acknowledge encephalitis as a known, albeit rare, adverse reaction to live-attenuated varicella vaccines, including instances with fatal outcomes.
Healthcare providers are urged to advise patients and their caregivers to seek immediate medical attention if any symptoms suggestive of brain inflammation arise after vaccination. These symptoms can include persistent headaches, altered mental status, or seizures.
The update also serves as a crucial reminder for clinicians to thoroughly assess patients for any immunocompromising conditions before administering live vaccines. Furthermore, it emphasizes the importance of comprehensive post-vaccination counseling for patients and their families.
This revised guidance will also apply to combination measles,mumps,rubella,and varicella (MMRV) vaccines,such as Priorix-Tetra and ProQuad,which contain the same live-attenuated varicella component. The updated product information for these vaccines will include more specific descriptions of encephalitis symptoms and their typical timing, empowering both clinicians and patients to recognize early warning signs and seek timely medical intervention.
While these updates address potential risks, it is vital to note that serious neurological events associated with varicella vaccines remain exceptionally rare. A 2024 case series analyzing 15 years of data documented 20 instances of varicella vaccine-associated meningitis or encephalitis in immunocompetent children and adolescents. These cases, identified through advanced diagnostic methods, underscore the rarity of such occurrences.
A comprehensive global review of live-attenuated varicella vaccines, spanning 22 years and analyzing over 212 million doses administered between 1995 and 2017, indicated a meaningful decrease in common adverse events over time. Serious adverse events were found to be extremely rare, occurring at a rate of 0.8 per million doses. More recently, a Chinese postmarketing study involving over 7.4 million administered doses also reported a low incidence of serious adverse events.