Enhanced placental antibody transfer efficiency with longer interval between maternal respiratory syncytial virus vaccination and birth

We conducted a prospective cohort study at 2 academic medical centers between September 20, 2023 and March 21, 2024. Individuals who received the respiratory syncytial virus (RSV) vaccine were enrolled. Maternal and cord blood samples (dyads) were collected at delivery, and capillary blood samples were obtained from a subset of infants at 2 months of age. The study examined how gestational age at vaccination and the time elapsed from vaccination to delivery impacted the transfer of maternal antibodies to the fetus, measured in umbilical cord blood, and their persistence in infants peripheral blood at 2 months of age.