Hybrid immunity to SARS-CoV-2 during pregnancy provides more durable infant antibody responses compared to natural infection alone.

BACKGROUND: Hybrid immunity (infection plus vaccination) may increase maternally-derived SARS-CoV-2 antibody responses and durability vs. infection alone. METHODS: Prospective cohort of pregnant participants with prior SARS-CoV-2 infection (anti-nucleocapsid IgG+, RT-PCR + or antigen+) and their infants had blood collected in pregnancy, delivery/birth, and postpartum tested for anti-spike (anti-S) IgG and neutralizing antibodies (neutAb). RESULTS: Among 107 participants at enrollment, 40% were unvaccinated and 60% were vaccinated (received ≥1 dose); 102 had previous SARS-CoV-2 infection in pregnancy (median 19 weeks gestation); 5 were diagnosed just prior to prior to pregnancy (median 8 weeks). At delivery, fewer unvaccinated participants (87% anti-S IgG+, 86% neutAb) and their infants (86% anti-S IgG+, 75% neutAb) had anti-S IgG + or neutAb compared to vaccinated participants and their infants (100%, p ≤ 0.01 for all). By 3-6 months postpartum, 50% of infants of unvaccinated participants were anti-S IgG + and 14% had neutAb, vs. 100% among infants of vaccinated participants (all p < 0.01), with lower median antibody responses (anti-S IgG log10 1.95 vs. 3.84 AU/ml, p < 0.01; neutAb log10 1:1.34 vs. 1:3.20, p = 0.11). CONCLUSIONS: In pregnant people with prior SARS-CoV-2, vaccination before delivery provided more durable maternally-derived antibody responses than infection alone in infants through 6 months.