Review by Vaccine Integrity Project supports Tdap vaccination during pregnancy

The two observational studies that addressed pertussis-related infant death suggested a reduced risk of death after maternal vaccination, with a greater benefit in areas of higher disease prevalence.

Among eight randomized trials and 25 observational studies reporting on safety, no elevated risk of adverse pregnancy outcomes was noted for stillbirth, preterm birth, preeclampsia (severe blood-pressure condition of pregnancy), eclampsia (progression of preeclampsia involving coma or seizures), or chorioamnionitis (infection of the amniotic fluid, placenta, or membranes around the fetus) in the infants of vaccinated mothers.

Likewise, the vaccine wasn’t linked to newborn congenital anomalies, poor growth, admission to a neonatal intensive care unit (NICU), or death.

Five randomized trials that reported on pregnancy-specific adverse events suggested no increased risk of premature contractions, premature labor, premature rupture of membranes (PROM), preterm PROM, or vaginal or postpartum hemorrhage.

“The safety profile remains consistently strong across a large body of research, giving prospective parents confidence that they can safely protect their newborns from a serious disease that infected tens of thousands of people last year,” Rochelle Walensky, MD, MPH, the VIP’s medical adviser and professor of medicine at Harvard Medical School, said in a VIP news release. 

‘Effective transfer of pertussis antibodies’

“Our findings update and align with prior reviews that have demonstrated effective transfer of pertussis antibodies through maternal vaccination, combined with no meaningful increase in an exhaustive list of adverse events during pregnancy or infancy,” the authors wrote. 

“Organizations or institutions aiming to formulate, update, or reaffirm recommendations for Tdap vaccination during pregnancy may prioritize outcomes differently than we have for the purposes of this review, which is intended to be a comprehensive summary that is not tailored for a particular decision scenario,” they added.

Our findings update and align with prior reviews that have demonstrated effective transfer of pertussis antibodies through maternal vaccination, combined with no meaningful increase in an exhaustive list of adverse events during pregnancy or infancy.

Study limitations included multiple studies that relied on common data sources, the relative rarity of the studied events, and the methodologic limitations of eligible studies. Yet, with the large number of participants, “We would expect that a signal around any safety issues would emerge,” Emily Senerth, MS, MPH, a consultant researcher for the Evidence Foundation, said during today’s Association of Health Care Journalists webinar on the report.

To support evidence-based decision-making about vaccination, the authors said future research could include stratification of outcome data based on different gestational ages at vaccination, comprehensive review and re-evaluation of outcome data and risk-of-bias judgments from previous reviews, and continued review of the published literature.