Observational safety study of febrile convulsion following first dose MMRV vaccination in a managed care setting
Section snippets
Background
ProQuad™, a combined formulation of measles, mumps, rubella, and varicella (MMRV) vaccine that contains components of two Merck vaccines, MMR-II™(MMR) and VARIVAX™ (V), was approved in the United States (US) in September 2005. Before MMRV was available, MMR and V were usually given concomitantly as two separate injections [1]. The new combined vaccine offers several advantages [2]. For parents and providers, the administration of a single vaccine, compared to two, can reduce the time, effort
Study setting
Kaiser Permanente Southern California (KPSC) is a large managed care organization that geographically spans from Bakersfield in the Southern San Joaquin Valley to San Diego, at the Mexican border. In 2006, KPSC had a membership of over 3.2 million, with a racial/ethnic composition similar to that seen in the source population. The majority of healthcare for members is delivered in one of 12 medical centers or their affiliated outpatient facilities. A fraction of emergent and specialty care is
Cohort characteristics
Of the 31,298 children in the index cohort, 31,043 (99%) were between the ages of 12 and 23 months and 255 were ages 24–60 months (Table 1). There were 15,337 (49%) girls and approximately 7000 children (22%) were non-Hispanic Whites. Nearly a third of vaccines were administered from February through April and less than 20% from November through January.
Results of adjudication of potential convulsion events
Of the 370 potential convulsion events, 138 cases had a claims record or visit outside the KPSC system, while 232 cases were seen within the
Discussion
In this report, we observed a modestly increased incidence of febrile convulsion in children receiving MMRV as compared to an historical comparison group that received MMR + V. This increase was concentrated in days 5–12 following vaccination as expected from the increased incidence of fever during that period in clinical trials [3], [4], [5], [6], [7]. This increased risk was attenuated by the end of 1 month of follow-up, with little overall difference in risk. For days 5–12 following
Acknowledgements
The authors thank the members of the Safety Review Committee (Drs. Allen Hauser (chair, Columbia University), Neal Halsey (Johns Hopkins University) and Samy Suissa (McGill University) for their critical and thoughtful comments and members of the adjudication panel (Drs. S. Michael Marcy (chief), Robert (Bo) Riewerts and Suresh Gurbani, Kaiser Permanente Southern California) for their diligent review of potential cases of febrile convulsion. Ms. Bianca Cheung (Kaiser Permanente Southern
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