Maternal and Neonatal Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Immunoglobulin G Levels After the Pfizer-BioNTech Booster Dose for Coronavirus Disease 2019 (COVID-19) Vaccination During the Second Trimester of Pregnancy.

Objective: To evaluate maternal and neonatal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) immunoglobulin G (IgG) antibody levels at birth after a third (booster) dose of the Pfizer-BioNTech messenger RNA (Pfizer) coronavirus disease 2019 (COVID-19) vaccine during the second trimester of pregnancy, and compare them with those in women who received two vaccine doses during the second trimester.

Methods: We conducted a prospective cohort study of women admitted to the delivery ward at a single center who received the third Pfizer COVID-19 vaccine dose (booster group) at 17-30 weeks of pregnancy and who did not have previous SARS-CoV-2 infection. Maternal and neonatal antibody levels were measured on admission for delivery and in the umbilical cord blood after birth.