Bottom line For every 2,300 children receiving the MMRV combination vaccine (Proquad) instead of the measles-mumps-rubella vaccine and the varicella vaccine (MMR-varicella) separately, one additional child will experience a febrile seizure. (Level of evidence = 2b)
Synopsis The measles vaccine is associated with an increased risk of febrile seizure 1 to 2 weeks after administration. To determine whether the risk of febrile seizure increases with MMRV, these researchers analyzed data from the Vaccine Safety Datalink (VSD), a vaccine safety surveillance system that captures data on 9 million members of eight US managed care organizations. The VSD is updated weekly with vaccine administration data and outcomes. The dataset included all children aged 12 to 23 months who received their first dose of the MMRV vaccine (83,107); the rate of febrile seizure was compared with children who received the MMR-varicella vaccines (376,354) during the prior 8 years. Febrile seizure was defined by the treating physician. Seizure risk for the 7 to 10 days after administration was higher with MMRV than with MMRvaricella
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, with an additional 4.3 febrile seizures per 10,000 doses of MMRV instead of MMR-varicella (95% CI, 2.6-5.6). This translates to one additional seizure for every 2,300 doses of combination MMRV given instead of two separate vaccines (number needed to treat to harm = 2,300).
Klein NP, Fireman B, Yih WK, et al; Vaccine Safety Datalink. Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures. Pediatrics. 2010;126(1):e1-e8.
