Prenatal tetanus, diphtheria, acellular pertussis vaccination and attention deficit hyperactivity disorder.

As prenatal vaccinations become more prevalent, it is important to assess potential safety events. This study investigates the association between prenatal tetanus, diphtheria, acellular pertussis (Tdap) vaccination and attention deficit hyperactivity disorder (ADHD) risk in offspring. Retrospective cohort study of mother-child pairs born 1/1/2011-12/31/2014 at Kaiser Permanente Southern California. Tdap vaccination during pregnancy was obtained from electronic medical records. ADHD was defined by International Classification of Diseases, 9th/10th Revision codes and ADHD medications after age 3 years. Children were followed to first ADHD diagnosis, end of membership, or end of follow-up (12/31/2018). Cox proportional hazards models estimated the unadjusted/adjusted hazard ratios (HR) for the association between maternal Tdap vaccination and ADHD, with inverse probability of treatment weighting (IPTW) to adjust for confounding. Of 128,756 eligible mother-child pairs, 85,607 were included in the final sample. ADHD incidence rate was 3.41 per 1,000 person-years in the Tdap vaccinated and 3.93 per 1,000 person-years in the unvaccinated (HR: 1.01, 95% confidence interval [CI]: 0.88, 1.16). The IPTW-adjusted analyses showed no association between prenatal Tdap vaccination and ADHD in offspring (HR: 1.00, 95% CI: 0.88, 1.14). Prenatal Tdap vaccination was not associated with ADHD risk in offspring, supporting recommendations to vaccinate pregnant women.