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

Abstract

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.

Maternal and Neonatal Immune Responses Following COVID-19 Infection and Vaccinations in Pregnancy

“…Our results coincide with previous reports showing antibody levels among pregnant women to be significantly higher after the third dose compared to the second dose [19,20,26] and significantly higher after the second dose compared to recovered women [9,12,27]. Similar patterns were demonstrated in neonatal antibody levels [9,12,19,20,27].…”

“…Published reports have confirmed the enhanced humoral response of almost all patients to the third dose, especially in populations with a low humoral response or waning immunity after the first and second doses [28][29][30]. In pregnant women and their neonates, recent studies have shown that similar to the first and second doses of the BNT162b2 vaccine, the third dose is successful in generating a remarkable humoral immune response of SARS-CoV-2 IgG, as well as being safe [18][19][20]. Moreover, a Norwegian population-based cohort study suggested there was a lower risk of a positive test for SARS-CoV-2 during the first 4 months of life among infants born to mothers who were vaccinated during pregnancy [31].…”

“…Recent studies have shown that, similar to the first and second doses of the BNT162b2 vaccine, the third dose is also safe in pregnancy and effective in generating a significant humoral immune response of SARS-CoV-2 IgG in pregnant women and their fetuses. [18][19][20][21].…”

Transplacental transmission of SARS‐CoV‐2 immunoglobulin G antibody to infants from maternal COVID‐19 vaccine immunization before pregnancy

“…The impact of immunization timing and vaccine dose on SARS‐CoV‐2 transplacental antibody transfer may influence neonatal seroprotection. According to previous studies, the COVID‐19 vaccine of pregnant women during the second trimester could be effective to achieve maternal protection and newborn safety during the pandemic 21,24,25 . In this study, we have found that the levels of SARS‐CoV‐2 antibodies were higher in infants from mothers immunizing the COVID‐19 vaccine than unvaccinated before pregnancy.…”

“…According to previous studies, the COVID‐19 vaccine of pregnant women during the second trimester could be effective to achieve maternal protection and newborn safety during the pandemic. 21 , 24 , 25 In this study, we have found that the levels of SARS‐CoV‐2 antibodies were higher in infants from mothers immunizing the COVID‐19 vaccine than unvaccinated before pregnancy. Although the level of SARS‐CoV‐2 IgG antibody decreased with the age of infants, significantly higher SARS‐CoV‐2 IgG antibodies levels in infants from the maternal 3‐dose of inactivated COVID‐19 vaccine before pregnancy compared with the 2‐dose.…”