Maternal-neonatal transfer of SARS-CoV-2 immunoglobulin G antibodies among parturient women treated with BNT162b2 messenger RNA vaccine during pregnancy

BACKGROUND: The exclusion of pregnant women from initial COVID-19 messenger RNA vaccine trials raised hesitancy regarding the benefits of vaccination for pregnant women, hence little is nwטnkabout vaccines’ efficacy in this population.
OBJECTIVE: odetermine the וatanoen-וanretamtransplacental trans­fer of SAR.S-CoV-2 antibodies among vaccinated parturient women. A control group of COVID-19-recovered patients was included to compare the immunoglobulin G levels between vaccinated and recovered patients.
STUDY DESIGN: This is a prospective cohort study conducted in a single tertiary medical center in וsrael between February and March 2021; parturient women vaccinated with the BNT162b2 messenger RNA vaccine during pregnancy were included and compared wilh COVI0-19-recovered parturient women. SARS-CoV-2 immunoglobulin G antibodies were mea­sured in matemal and cord sera, dried blood spot sampוes taken from newboms, and breast milk samples. The pזimary aim was to determine whether neonatal cord and dזied blood spot samples were positive for SARS-CoV-2 antibodies and to evaוuate the transfer ratio, defined as cord blood immunoglobulin G divided by matemal immunoglobulin G levels.
RESULTS: The study included 64 vaccinated parturient women and 11 parturient women who had COVID-19 during pregnancy. AII matema blood sera samples and 98.3% of the cord blood sera samples were posi­tive for SARS-Cov-2 immunoglobulin G wilh median concentrations of 26.1 (interquartile range, 22.0-39.7} and 20.2 (interquartile range, 12.7 -29.0), respectively. Similaז1y, 96.4% of neonatal blood spot samples and aוו breast milk samples were positive for SARS-CoV-2 immunoglobulin G with median concentrations of 11 .0 unterquartile range, 7.2-12.8) and 4.9 (interquartile range, 3.8-6.0), respectively. There was a significant positive correlation between matemal serum levels of SARS-CoV-2 immu­noglobulin G and cord blood (r=0.483; P=.0001), neonatal blood spot (r=0.515; P=.004), and breast milk levels (r=0.396; P=.005) of SARS­CoV-2 immunoglobulin G. The median placental transfer ratio of SARS­COV-2 immunoglobulin G was 0.77. Comparison of vaccinated and recov­ered COVID-19 patients revealed significantly higher SARS-CoV-2 immu­noglobulin G levels in matemal serum and cord blood among vaccinated women (P<.0001).
CONCLUSION: Our study demonstrated the efficient transfer of SARS­ CoV-2 immunoglobulin G across the placenta in women, vaccinated with lhe BNT162b2 messenger RNA vaccine during pregnancy, to their neo­nates, with a positive noitaוerrocbetween וametamserum and cord blood antibody concentrations. וn addition to maternal protection against COVI0-19, the vaccine may also provide neonatal humoral immunity.