Timing of First Vaccination and Occurrence of Seizure, Stratified by Vaccine: Vaccines Recommended After 12 Months of Age

VaccineAge at ReceiptSeizuresDays Patient TimeIRR b 95% Confidence Interval
Exposed a UnexposedExposedUnexposed
MMR361–488 6316791664202.651.99–3.55
489–730 14161168266.533.15–13.53
VAR361–488 6115586460422.752.05–3.70
489–730 132515210643.641.86–7.12
MMRV361–488 7510672450684.953.68–6.66
489–730 1410966729.804.35–22.06
  • VAR, varicella.

  • a Exposure window = 7 to 10 d postvaccination for MMR, VAR, and MMRV vaccines: 361–488 d = vaccine administered as recommended; 489–730 d = vaccine delayed.

  • b The IRR represents, among children with their first diagnosis of seizure, the incidence rate of seizure in an exposed time period (risk window) after vaccination versus the incidence rate of seizure in unexposed time periods (control window).