VACCINE SAFETY DATALINK PROJECT - A NEW TOOL FOR IMPROVING VACCINE SAFETY MONITORING IN THE UNITED-STATES

Objective. To fill the large ''gaps and limitations'' in current scien tific knowledge of rare vaccine adverse events identified in recent re views of the Institute of Medicine. Methods. Computerized information on immunization, medical outcomes, and potential confounders on more t han 500 000 children 0 to 6 years of age is linked annually at several health maintenance organizations to create a large cohort for multipl e epidemiologic studies of vaccine safety. Results. Analysis of 3 year s of follow-up data shows that 549 488 doses of diphtheria-tetanus-per tussis (DTP) and 310 618 doses of measles-mumps-rubella (MMR) vaccines have been administered to children in the study cohort. Analyses for associations between vaccines and 34 medical outcomes are underway. Sc reening of automated data shows that seizures are associated with rece ipt of DTP on the same day (relative risk [RR], 2.1; 95% confidence in terval [CI], 1.1 to 4.0) and 8 to 14 days after receipt of MMR (RR 3.0 ; 95% CI, 2.1 to 4.2). The diversity of vaccination exposures in this large cohort permits us to show that an apparent association of seizur es 8 to 14 days after Haemophilus influenzae type b vaccine (RR, 1.6; 95% CI, 1.2 to 2.1) was attributable to confounding by simultaneous MM R vaccination; the association disappears with appropriate adjustment (RR, 1.0; 95% CI, 0.7 to 1.4). Conclusion. Preliminary design, data co llection, and analytic capability of the Vaccine Safety Datalink proje ct has been validated by replication of previous known associations be tween seizures and DTP and MMR vaccines. The diversity in vaccine admi nistration schedules permits potential disentangling of effects of sim ultaneous and combined vaccinations. The project provides a model of p ublic health-managed care collaborations in addition to an excellent i nfrastructure for safety and other studies of vaccines.