Transplacental transmission of SARS‐CoV‐2 immunoglobulin G antibody to infants from maternal COVID‐19 vaccine immunization before pregnancy

Abstract The coronavirus disease 2019 (COVID‐19) vaccine generates functional antibodies in maternal circulation that are detectable in infants, while the information is restricted to the usage of COVID‐19 vaccine during pregnancy. In this study, we aimed to evaluate the effect of maternal COVID‐19 vaccines before pregnancy. Infants were included from mothers with no inactivated COVID‐19 vaccine, 1‐, 2‐, and 3‐dose before pregnancy, and severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) immunoglobulin G (IgG) antibodies were tested. Comparative analysis was done between the groups. A total of 130 infants were enrolled in the study. Significantly higher levels of SARS‐CoV‐2 IgG antibodies in infants born to mothers with 3‐dose COVID‐19 vaccine before pregnancy compared with 1‐ and 2‐dose groups ( p < 0.0001). The levels of antibodies decreased significantly with age in infants born to mothers with the 3‐dose COVID‐19 vaccine before pregnancy ( r = −0.338, p = 0.035), and it was still higher than that 2‐dose COVID‐19 vaccine group. The maternal SARS‐CoV‐2 antibodies produced from the inactivated COVID‐19 vaccine before pregnancy can be transferred to newborns via the placenta. Maternal immunization with 3‐dose of the COVID‐19 vaccine before pregnancy could be more beneficial for both mothers and infants.