Maternal and cord blood sera were collected from 20 parturients who received the BNT162b2 vaccine. All women and infants were positive for anti S- and anti-RBD-specific IgG. Cord blood antibody concentrations were correlated to maternal levels and to time since vaccination. Antenatal SARS-CoV-2 vaccination may provide maternal and neonatal protection.

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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 years and a median gestational age of 393/7 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 and 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 (Rs= 0.72; P<0.001 and Rs = 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 (Rs = 0.71; P =0.001 and Rs= 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.

Background COVID-19 during pregnancy and early infancy can result in severe disease. Evaluating the effect of gestational age at the time of SARS-CoV-2 vaccination on maternal antibody levels and transplacental antibody transfer has important implications for maternal care and vaccination strategies. Methods Maternal and cord blood sera were collected from mother/newborn dyads (n=402), following term delivery after antenatal two-dose SARS-CoV-2 BNT162b2 mRNA vaccination. SARS-CoV-2 spike protein (S) and receptor binding domain (RBD)-specific IgG levels were evaluated in the samples collected. Results Median anti-S and anti-RBD-specific IgG levels in maternal sera at the time of delivery were lowest following 1 st trimester vaccination (n=90) (anti-S IgG: 76 AU/mL, anti-RBD-specific IgG: 478 AU/mL), intermediate in those vaccinated in the 2 nd trimester (n=124) (anti-S IgG: 126 AU/mL, anti-RBD-specific IgG: 1263 AU/mL), and highest after 3 rd trimester vaccination (n=188) (anti-S IgG: 240 AU/mL, anti-RBD-specific IgG: 5855 AU/mL). Antibody levels in neonatal sera followed a similar pattern and were lowest following antenatal vaccination in the 1 st trimester (anti-S IgG: 126 AU/mL, anti-RBD-specific IgG: 1140 AU/mL). In a subgroup of parturients vaccinated in the 1 st trimester (n=30), a third booster dose was associated with significantly higher maternal and neonatal antibody levels. Conclusions These results suggest a considerable antibody waning throughout pregnancy in those vaccinated at early gestation. The observed boosting effect of a third vaccine dose, hints to its potential benefit in those who completed the two-dose vaccine series at early pregnancy or prior to conception. The impact of antenatal immunization timing on SARS-CoV-2 transplacental antibody transfer may influence neonatal seroprotection.

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