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Observational safety study of febrile convulsion following first dose MMRV vaccination in a managed care setting

Steven J Jacobsen1, Bradley K Ackerson, Lina S Sy

  • 1Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, CA 91101, USA. steven.j.jacobsen@kp.org

Vaccine
|June 13, 2009
PubMed
Abstract

Insights

The measles, mumps, rubella, varicella (MMRV) vaccine showed a higher risk of febrile convulsion in the 5-12 days post-vaccination period compared to separate vaccines. This increased risk needs to be weighed against the benefits of the combined vaccine.

Area of Science:

  • Pediatric Vaccinology
  • Immunization Safety
  • Public Health

Background:

  • The combined measles, mumps, rubella, varicella (MMRV) vaccine was recently approved in the US.
  • Pre-licensure trials indicated a potential increase in fever following MMRV vaccination.
  • Post-licensure studies are crucial for assessing vaccine safety in real-world settings.

Purpose of the Study:

  • To evaluate the incidence of febrile convulsion after MMRV vaccination.
  • To compare the risk of febrile convulsion between MMRV and separately administered measles, mumps, rubella, and varicella (MMR+V) vaccines.

Main Methods:

  • A retrospective cohort study included children aged 12-60 months who received MMRV or MMR+V.
  • Subjects were matched on age, sex, and vaccination date.
  • Febrile convulsion cases were identified via administrative data and expert adjudication.

Main Results:

  • No significant difference in overall febrile convulsion risk was observed within 30 days post-vaccination (RR=1.10).
  • However, a statistically significant increase in febrile convulsion risk was found between days 5-12 post-vaccination (RR=2.20).
  • The incidence rates were 0.70/1000 for MMRV and 0.32/1000 for MMR+V during this specific period.

Conclusions:

  • The MMRV vaccine is associated with an elevated risk of febrile convulsion during days 5-12 post-vaccination.
  • This finding aligns with increased fever and rash observed in clinical trials.
  • The heightened risk during this specific window warrants communication and careful consideration alongside the advantages of combined vaccination.

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