The association of maternal SARS-CoV-2 vaccination-to-delivery interval and the levels of maternal and cord blood antibodies.

Abstract

ObjectiveTo evaluate the correlation of maternal and cord blood levels of SARS‐CoV‐2 antibodies in pregnant women immunized against COVID‐19.MethodsA prospective cohort study was performed of pregnant women who delivered at a single university affiliated tertiary medical center. Women who received the COVID‐19 vaccine (BNT162b2 Pfizer©) were approached. The correlation between levels of maternal sera and umbilical cord SARS‐CoV‐2 specific IgG was assessed.ResultsOverall, 58 women were included; of them, 19 had received a single dose and 39 received two doses of the COVID‐19 vaccine. Positive levels of umbilical cord IgG were found in 13/19 (68.4%) and 38/39 (97.4%) women after the administration of a single dose and two doses of the vaccine, respectively. The levels of SARS‐CoV‐2 IgG antibodies in the maternal sera of vaccinated women were positively correlated to their respective concentrations in cord blood sera (ρ = 0.857; R2 linear = 0.719; P < 0.001). Thirteen days after vaccination, the ratio of maternal‐to‐umbilical cord anti Spike IgG antibodies was approximately 1, indicating relatively similar levels in maternal and cord sera.ConclusionAfter the SARS‐CoV‐2 vaccine, levels of maternal and cord blood antibodies were positively correlated, especially when tested after 13 days following administration of the first dose of the vaccine.