No association was observed between prenatal tetanus, diphtheria, and acellular pertussis (Tdap) vaccination and an increased risk of autism spectrum disorder (ASD) in children, according to findings published in Pediatrics.
Research investigating both maternal and child outcomes after prenatal Tdap vaccination have not assessed outcomes that occur over the long term, such as risk of ASD, which is of significant public interest. In the current study, the authors conducted a retrospective cohort review of mother-child pairs from 2011 to 2014, at Kaiser Permanente Southern California hospitals. A total of 81,993 children were included in the study, and the prevalence of prenatal Tdap vaccination ranged from 26% for the 2012 birth cohort to 79% for the 2014 birth cohort.
The follow-up time ranged from 1.2 to 6.5 years and tended to be longer among those who had not been vaccinated. The proportion of children diagnosed with ASD declined from 2.0% to 1.5% in the unvaccinated group and from 1.8% to 1.2% in the vaccinated group. The ASD incidence rate was 3.78 per 1000 person-years in the vaccinated arm vs 4.05 per 1000 person-years in the unvaccinated arm, for an unadjusted hazard ratio (HR) of 0.98 (95% CI, 0.88-1.09). The inverse probability of treatment weighting-adjusted analyses demonstrated that prenatal vaccination with Tdap was not associated with an increased risk of ASD (HR 0.85; 95% CI, 0.77-0.95).
“Future studies with additional birth years and longer follow-up can add to the scientific evidence about Tdap vaccination during pregnancy and ASD in offspring,” the researchers concluded.