Maternal tetanus, diphtheria, and acellular pertussis (Tdap) vaccination during pregnancy isn't associated with adverse outcomes for offspring through early childhood, a new study suggests. Researchers examined data on 625,643 live births in Ontario, Canada, from April 2012 to March 2017. A total of 12,045 (1.9%) infants exposed to Tdap in utero were propensity matched to 60,225 unexposed babies. Overall, there were no significant associations between Tdap exposure in utero and an increased risk of adverse outcomes in childhood, the researchers report in Pediatrics. "We already know that there are very strong benefits of Tdap vaccination during pregnancy, which has been shown to significantly reduce pertussis infections in young infants, who are most vulnerable to this particular infection," said senior study author Deshayne Fell of the school of epidemiology and public health at the University of Ottawa and the Children's Hospital of Eastern Ontario (CHEO) Research Institute. "Concerns about safety is one of the key reasons that women cite for not getting vaccinated with Tdap or influenza vaccine during pregnancy, so this study can help provide additional reassurance to what we already know about safety of maternal immunization," Fell said by email. In particular, the study found no significant association between maternal Tdap vaccination and all-cause injury rates, asthma, otitis media, or sensory disorders. Some adverse outcomes were significantly lower among Tdap-exposed infants than among unexposed infants, the authors note. Compared to unexposed infants, babies exposed to Tdap had significantly lower incidence rate ratios for upper respiratory infections (aIRR 0.94), gastrointestinal infections (aIRR 0.85), as well as utilization of urgent care and inpatient services (aIRR 0.93). It's possible that unmeasured confounders influenced the results, the study team acknowledges. The study was also underpowered for certain rare adverse outcomes such as neoplasm. Even so, the results aren't surprising, and confirm the safety and effectiveness of Tdap in pregnancy, said Dr. Yvonne Maldonado, chief of pediatric infectious diseases at Stanford University School of Medicine and medical director of infection control and prevention at Lucile Packard Children's Hospital at Stanford in California. The results validate the use of maternal Tdap vaccination during pregnancy, which is the current standard of care, Dr. Maldonado, who wasn't involved in the study, said by email. "We wouldn't expect to see any association between vaccination and health outcomes in children," said Dr. Annette Regan, an assistant professor at the University of San Francisco who wasn't involved in the study. Indeed, there are a lot of data to show the safety of vaccination, and that maternal antibodies leave the babies' immune system within months after birth, Dr. Regan said by email. "However, we know some people struggle with the decision to get vaccinated or not while pregnant — even though it so important for protecting infants from deadly respiratory infections," Dr. Regan said. "Having results from a study like this should be reassuring for those who are in the process of deciding whether to get vaccinated during pregnancy or not." —Lisa Rapaport Source
