Efficient maternofetal transplacental transfer of anti- SARS-CoV-2 spike antibodies after antenatal SARS-CoV-2 BNT162b2 mRNA vaccination

Background Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) during pregnancy and early infancy can result in severe disease. Evaluating the serologic response after maternal vaccination during pregnancy and subsequent transplacental antibody transfer has important implications for maternal care and vaccination strategies. Objective To assess maternal and neonatal SARS-CoV-2 antibody levels after antenatal mRNA vaccination. Design, Setting, and Participants This study took place at Hadassah Medical Center in Jerusalem, Israel in February 2021. Maternal and cord blood sera were collected for antibody measurement from mother/newborn dyads following antenatal vaccination. Exposure SARS-CoV-2 BNT162b2 mRNA vaccination. Main outcome and measures Spike protein (S) and receptor binding domain (RBD) - specific, IgG levels were evaluated in maternal and cord blood sera. Results The study cohort consisted of 20 parturients, with a median maternal age of 32 y ears and a median gestational age of 39 3/7 weeks at the time of delivery. The median time lapsed from the first and second doses of vaccine administration until delivery was 33 [IQR 30-37] and 11 [IQR 9-15] days, respectively. Of the 20 dyads, all women an d infants were positive for anti S- and anti-RBD-specific IgG. Anti-S and anti-RBD-specific IgG levels in maternal sera were positively correlated to their respective concentrations in cord blood (ρ s = 0.72; P<0.001 and ρ s = 0.72; P <0.001, respectively). Anti-S and anti-RBD-specific IgG titers in cord blood were directly correlated with time lapsed since the administration of the first vaccine dose (ρ s = 0.71; P =0.001 and ρ s = 0.63; P=0.004, respectively). Conclusion and Relevance In this study, SARS-CoV-2 mRNA vaccine administered during pregnancy induced adequate maternal serologic response with subsequent efficient transplacental transfer. Our findings highlight that vaccination of pregnant women may provide maternal and neonatal protection from SARS-CoV-2 infection.