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Comparative Study
. 2010 Jul;126(1):e1-8.
doi: 10.1542/peds.2010-0665. Epub 2010 Jun 29.

Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures

Nicola P Klein  1 , Bruce Fireman, W Katherine Yih, Edwin Lewis, Martin Kulldorff, Paula Ray, Roger Baxter, Simon Hambidge, James Nordin, Allison Naleway, Edward A Belongia, Tracy Lieu, James Baggs, Eric Weintraub; Vaccine Safety Datalink
Affiliations
Comparative Study

Measles-mumps-rubella-varicella combination vaccine and the risk of febrile seizures

Nicola P Klein et al. Pediatrics. 2010 Jul.

Abstract

Objective: In February 2008, we alerted the Advisory Committee on Immunization Practices to preliminary evidence of a twofold increased risk of febrile seizures after the combination measles-mumps-rubella-varicella (MMRV) vaccine when compared with separate measles-mumps-rubella (MMR) and varicella vaccines. Now with data on twice as many vaccine recipients, our goal was to reexamine seizure risk after MMRV vaccine.

Methods: Using 2000-2008 Vaccine Safety Datalink data, we assessed seizures and fever visits among children aged 12 to 23 months after MMRV and separate MMR + varicella vaccines. We compared seizure risk after MMRV vaccine to that after MMR + varicella vaccines by using Poisson regression as well as with supplementary regressions that incorporated chart-review results and self-controlled analyses.

Results: MMRV vaccine recipients (83,107) were compared with recipients of MMR + varicella vaccines (376,354). Seizure and fever significantly clustered 7 to 10 days after vaccination with all measles-containing vaccines but not after varicella vaccination alone. Seizure risk during days 7 to 10 was higher after MMRV than after MMR + varicella vaccination (relative risk: 1.98 [95% confidence interval: 1.43-2.73]). Supplementary analyses yielded similar results. The excess risk for febrile seizures 7 to 10 days after MMRV compared with separate MMR + varicella vaccination was 4.3 per 10,000 doses (95% confidence interval: 2.6-5.6).

Conclusions: Among 12- to 23-month-olds who received their first dose of measles-containing vaccine, fever and seizure were elevated 7 to 10 days after vaccination. Vaccination with MMRV results in 1 additional febrile seizure for every 2300 doses given instead of separate MMR + varicella vaccines. Providers who recommend MMRV should communicate to parents that it increases the risk of fever and seizure over that already associated with measles-containing vaccines.

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