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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. Antibody levels for the booster group were compared with those in a historical control group of pregnant women who received their second vaccine dose (twodose group) within the same gestational age window. RESULTS:Between October 2021 and February 2022, antibody levels were measured in 121 women and 109 neonates at a mean6SD of 15.363.9 weeks after booster vaccination. Neonatal titers measured two times higher than maternal titers, with inverse correlation between maternal and neonatal titers at birth and time interval from third vaccination. The two-dose group included 121 women and 107 neonates, with antibody levels measured at a mean6SD of 14.662.6 weeks after the second dose. Median [interquartile range] maternal antibody titers were higher in the booster group (4,485 [2,569-9,702] AU/mL) compared with the twodose group (1,122 [735-1,872] AU/mL) (P,.001). Furthermore, neonatal antibody titers were higher in the booster group (8,773 [5,143-18,830] AU/mL) compared with the twodose group (3,280 [2,087-5,754] AU/mL) (P,.001).CONCLUSION: Maternal and neonatal SARS-CoV-2 IgG antibody titers after second-trimester maternal Pfizer COVID-19 vaccination were significantly higher after the booster dose compared with the two-dose vaccination series. Although there is uncertainty as to whether antibody levels correlate with protection, these data support the importance of booster vaccination during pregnancy to restore maternal and neonatal protection against COVID-19.

Background Protocols for preventing early‐onset group B streptococcal (GBS) neonatal infection may result in unnecessary antibiotics administration. Real‐time polymerase chain reaction (PCR) can provide a result within 30–60 min and has been found to be specific and sensitive for defining intrapartum GBS status. Objective To evaluate whether implementation of GBS fast real‐time PCR to all women who require GBS prophylaxis may reduce the use of maternal prophylactic antibiotics. Methods This prospective cohort study included women admitted to a single delivery ward who required prophylactic antibiotics either due to a positive antepartum GBS culture screening performed at 35–37 weeks or due to an unknown GBS status with an intrapartum risk factor. All the women were tested by a double vaginal swab (real‐time PCR and culture) as soon as it became apparent, they required antibiotic prophylaxis and prior to its administration. Results Between May 2019 and August 2020, 303 women met eligibility criteria and were enrolled, but four were excluded from the analysis due to failed culture or PCR tests. Of 299 women included in the study, 208 (69.5%) and 180 (60.2%) women, showed no evidence of GBS on intrapartum culture or PCR, respectively. Of 89 GBS antepartum carriers, 43 (48.3%) and 32 (35.9%) had negative intrapartum culture and PCR results, respectively. Of the 210 women with risk factors, 165 (78.5%) were culture negative and 148 (70.4%) had a negative PCR. Using intrapartum culture as the gold standard, intrapartum GBS real‐time PCR was found to have a sensitivity of 97.8% (95% confidence interval [CI] 92.3, 99.7) and a specificity of 85.6% (95% CI 80.1, 90.1). Conclusions Compared with antepartum universal culture screening or intrapartum risk‐factor assessment, the need for maternal antibiotic treatment may be substantially reduced by implementation of intrapartum GBS real‐time PCR, without compromising the sensitivity of GBS detection.

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