Rate of vertical transmission of coronavirus disease 2019 and effect of maternal vaccination: A prospective cohort study.

Background: We aimed to reveal the transmission rate of coronavirus disease 2019 (COVID‐19) and clinical features of congenital and neonatal COVID‐19 and to disclose the efficacy of maternally transferred antibodies by maternal vaccination against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Methods: This multicenter, prospective observational study included a comprehensive testing protocol with appropriate precautions. Mothers and infants were enrolled and classified into an active infection group (mothers with COVID‐19 at delivery), a postinfection group (mothers recovered from COVID‐19 during pregnancy), and a vaccination group (mothers vaccinated during pregnancy). Specimen collections, polymerase chain reaction assays, anti‐SARS‐CoV‐2 antibody measurements, and clinical examinations were conducted for 6 months from delivery. Results: Sixty‐nine mothers and 70 infants were enrolled. SARS‐CoV‐2 was detected in the placenta in 22% of the active infection group and in 21% of the postinfection group. Neither SARS‐CoV‐2 nor SARS‐CoV‐2‐specific IgM was detected in infants. No anomalies, functional disorders, or developmental problems were observed in infants for 6 months. Compared with the postinfection group, there was a significant increase in maternally transferred antibody titers in the vaccination group according to the number of vaccinations, which was maintained for longer than the first month of life. Conclusions: Vertical transmission of COVID‐19 was not observed despite a comprehensive testing protocol. SARS‐CoV‐2 was detected more often in the placenta, which appeared to prevent vertical transmission. Maternal vaccination increased maternally transferred antibody titers in infants and was considered immunologically efficient. Vaccination during pregnancy is considered important for preventing congenital, neonatal, and infantile COVID‐19. [ABSTRACT FROM AUTHOR]