Maternal antibody transfer rate of vaccination against SARS-CoV-2 before or during early pregnancy and its protective effectiveness on offspring.

This study focuses on maternal antibody transfer following vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) before or during early pregnancy and its potential protective effects on infants, providing scientific evidence for vaccination strategies. This prospective study tested the samples for SARS-CoV-2 IgG antibody titers and neutralizing capacity and tracked the infections after birth. Perform multivariate analysis of factors influencing antibody transfer rate, newborn antibody titers, and infant infection. Total 87.1% (122/140) women received coronavirus disease 2019 (COVID-19) vaccine before or during early pregnancy, and 28 of them had breakthrough infection. The maternal and neonatal IgG positive rates at delivery were 60.7% (85/140) and 60.8% (87/143), respectively. A positive correlation was found between neonatal and maternal IgG antibody titers. Compared with the median IgG antibody transfer rate of infected pregnant women, that of vaccinated but not infected pregnant women was higher (1.21 versus: 1.53 [two doses], 1.71 [three doses]). However, neonatal IgG antibodies were relatively low (174.91 versus: 0.99 [two doses], 8.18 [three doses]), and their neutralizing capacity was weak. The overall effectiveness of maternal vaccination in preventing infant infection was 27.0%, and three doses had higher effectiveness than two doses (64.3% vs. 19.6%). Multivariate analysises showed that in vaccination group women receiving three doses or in infection group women with longer interval between infection and delivery had a higher antibody transfer rate and neonatal IgG antibody titer. More than half of women vaccinated before or during early pregnancy can achieve effective antibody transfer to newborns. However, the neonatal IgG antibody titer is low and has a weak neutralizing capacity, providing limited protection to infants.