A longitudinal cohort study of childhood MMR vaccination and seizure disorder among American children

Measles (rubeola) is a highly contagious infectious disease with significant morbidity/mortality. Measles-Mumps-Rubella (MMR) is a live-attenuated vaccine used in the United States (US) to prevent measles. This retrospective longitudinal cohort study evaluated childhood MMR vaccination and the risk of a seizure episode and seizure disorder. The Independent Healthcare Research Database (IHRD) composed of records prospectively generated from Florida Medicaid was analyzed using SAS to identify persons continuously enrolled from birth for 120 months. Two cohorts were examined: 23,486 persons received at least one dose of MMR vaccine between 12 and 17 months (vaccinated) and 41,725 persons not receiving a measles-containing vaccine (unvaccinated). The daily incidence rate of an initial seizure episode (ICD-9 code: 780.3x) and seizure disorder (ICD-9 code: 345.xx) following an initial seizure episode diagnoses were examined using Cox proportional hazards ratio (HR) and time-trend models post-MMR vaccination compared to unvaccinated persons and in a self-controlled case-series (SCCS). The daily incidence rate of an initial seizure episode diagnosed from 6 to 11 days post-MMR vaccination in comparison to 12 to17 months among unvaccinated persons was significantly increased (unadjusted HR = 5.73, p