Maternal and cord anti-SARS-CoV-2-spike IgG following COVID-19 vaccination vs. infection during pregnancy: a prospective study, Israel October 2021-March 2022.

At the time of epidemic, receiving an additional COVID-19 vaccine dose in the third-trimester resulted in a higher IgG-GMC compared to the second-trimester. Relatively higher levels of maternal and cord IgG-GMC were achieved following vaccination than infection. Women infected during or before the first-trimester might benefit from an additional third-trimester dose to prevent peripartum infection and to passively immunize their newborn. The higher levels of maternal IgG-GMC in the Omicron period are suggestive of hybrid immunity.