Maternal-infant transfer of SARS-CoV-2 antibodies following vaccination in pregnancy: A prospective cohort study

Objectives: To measure and evaluate the impact of receiving severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines in pregnancy on immunoglobulin G (IgG) and immunoglobulin A (IgA) titres in maternal and infant samples. Design: Prospective cohort study. Setting: Tertiary obstetric centre. Population or Sample: 52 pregnant women who received one or more SARS-CoV-2 vaccine doses during pregnancy and their neonates. Methods: IgG and IgA concentrations against SARS-CoV-2 antigens were measured from samples collected at delivery and 4-6 weeks postpartum and compared using Spearman correlations. Main Outcome Measures: Maternal and infant IgG and IgA titres in response to vaccination and infection in pregnancy. Results: In maternal serum collected at delivery, participants without evidence of prior infection who received 3 + doses of a SARS-CoV-2 vaccine had higher Anti-Spike (S) IgG geometric mean concentrations (log10 AU/mL) (GMC) than those who received 2 doses (3 + Doses = 5.00, 2 Doses = 4.60, p = 0.08). The differences in IgG Anti-S GMC were statistically significant in cord serum, and in postpartum samples of maternal serum, infant serum and breast milk (Cord GMCs: 3 + Doses = 5.32, 2 Doses = 4.98, p < 0.05; Postpartum maternal serum GMCs: 3 + Doses = 5.25, 2 Doses = 4.57, p < 0.001; Postpartum infant serum GMCs: 3 + Doses = 5.10, 2 Doses = 4.72, p = 0.03; Postpartum breast milk GMCs: 3 + Doses = 2.61, 2 Doses = 1.94, p < 0.0001). Among participants with 3 + Doses, those with evidence of SARS-CoV-2 infection had statistically significant higher anti-S IgG GMCs than those without prior infection (Maternal serum at delivery: SARS-CoV-2+=5.65, SARS-CoV-2=5.00, p = 0.004; Cord: SARS-CoV-2+=5.68, SARS-CoV-2-=5.32, p = 0.02; Postpartum maternal serum: SARSCoV-2+=5.66, SARS-CoV-2-=5.25, p < 0.001; postpartum infant serum: SARS-CoV-2+=5.50, SARS-CoV-2=5.10, p = 0.003; Postpartum breast milk: SARS-COV-2+=3.25, SARS-COV-2-=2.61, p = 0.009). Significant positive correlations were found for anti-S IgG titres between paired maternal and infant samples at delivery and postpartum (Delivery: R = 0.91, p < 0.001; postpartum: R = 0.86, p < 0.001). Conclusions: Receipt of a SARS-CoV-2 vaccine and SARS-CoV-2 infection elicit strong IgG and IgA antibody responses in pregnant women with evidence of transplacental transfer to the fetus.