This prospective observational study was conducted at the Rabin Medical Center, Israel. Mothers were enrolled from September 2021 to mid-February 2022, prior to transfer to the delivery room, and followed at the Maternity and Infant Ward. The study was approved by the institutional ethics committee (RMC- 0275-21). Written informed consent was obtained from the participating mothers. Inclusion criteria included maternal recipient of at least one dose of the BNT162b2 mRNA COVID-19 vaccine or prior microbiologically-confirmed natural COVID-19 infection. Exclusion criteria included (a) preterm birth at \<34 weeks gestation; (b) congenital or acquired immune deficiency, including recipient of biological agents during the prior year to enrolment.
