MMRV Vaccine Increases Fever and Seizure Risk

Measles-mumps-rubella-varicella (MMRV) vaccination is associated with an increased risk of fever and seizure in young children, above that already associated with measles-containing vaccines, according to a recent study. The study, which was published in the June 29 online issue of Pediatrics, used Vaccine Safety Datalink data from 2000 to 2008, and evaluated seizure and fever visits among children ages 12 months to 23 months after MMRV and separate MMR plus varicella vaccines. Researchers found that with all measles-containing vaccines, seizure and fever significantly clustered seven to 10 days after vaccination, but this was not the case after varicella vaccination alone. In addition, during days seven to 10 after vaccination, the seizure risk was high after MMRV vaccination compared with after MMR plus varicella vaccination, with a relative risk of 1.98. Therefore, the researchers determined that MMRV vaccination leads to one additional febrile seizure for every 2,300 doses given instead of MMR plus varicella vaccines.

A previous preliminary study found that the MMRV vaccine is linked to a twofold increased risk of febrile seizures compared with separate MMR and varicella vaccines. The current study included data on twice as many vaccine recipients.