mRNA vaccines were found to be more effective in reducing the risk of fetal or neonatal death in pregnant women compared to non-mRNA vaccines, according to a recent study presented at the ACOG Annual Clinical & Scientific Meeting in San Francisco. 

Preeclampsia, preterm birth, and stillbirth are risks in patients with COVID-19 infection during pregnancy. Despite recommendations for vaccination, hesitancy remains due to limited pregnancy-specific data. This study compared the safety of Pfizer and Moderna (mRNA vaccines) and Johnson & Johnson (adenovirus vaccine).

A systematic search of Pubmed, Embase, and Cochrane Central was performed to identify studies comparing mRNA and non-mRNA vaccines. The meta-analysis included 8 observational studies, encompassing a total of 32,153 pregnant patients.

The analysis revealed that mRNA vaccines were associated with a significantly lower incidence of fetal death (P < .00001) compared to non-mRNA vaccines. Conversely, non-mRNA vaccines were associated with a lower incidence of fever (P < .00001). Subgroup analyses indicated that the Johnson & Johnson vaccine (Ad26.COV2.S) had a lower association with premature labor and delivery (P = .09) and missed and spontaneous abortion (P = .02) compared to the Pfizer vaccine. The leave-one-out analysis favored mRNA vaccines in reducing the risk of fetal or neonatal death, while non-mRNA vaccines were more effective in minimizing pyrexia, with low heterogeneity observed.

The authors reported no potential conflicts of interest.