High transferability of neutralizing antibodies against SARS-CoV-2 to umbilical cord blood in pregnant women with BNT162b2 XBB.1.5 vaccine - a retrospective cohort study

Coronavirus disease 2019 (COVID-19), when contracted by pregnant women, can lead to severe respiratory illness, rapid disease progression, and higher rates of intensive care unit admission. COVID-19 infection during pregnancy is associated with an increased risk of preterm delivery, cesarean section, fetal dysfunction, preeclampsia, and perinatal death. Additionally, vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) from pregnant women to their fetuses has been observed. While severe infections in neonates and infants are rare, newborns can experience serious consequences from COVID-19, despite their suboptimal humoral immune system protection. The amino acids in the structural proteins of SARS-CoV-2 are subjected to constant mutation. Since around January 2023, COVID-19, caused by infection with omicron-type SARS-CoV-2 variants, has been prevalent globally. Omicron-type SARS-CoV-2 variants can evade the immune response triggered by traditional mRNA-based COVID-19 vaccines, such as BNT162b2. Therefore, vaccination with a vaccine (BNT162b2 XBB.1.5) that can provide protection against omicron-type SARS-CoV-2 variants is recommended. Therefore, we examined the titers of anti-spike glycoprotein of SARS-CoV-2 IgG and IgA in the blood and umbilical cord blood obtained from pregnant women vaccinated with BNT162b2 XBB.1.5. The results showed that anti-spike glycoprotein of SARS-CoV-2 IgG and IgA titers were highest in the blood and cord blood obtained from pregnant women vaccinated with BNT162b2 XBB.1.5 at late gestational age (28-34 weeks). No serious side effects or adverse events caused by vaccination of pregnant women with BNT162b2 XBB.1.5 were observed in either pregnant women or newborns. In the future, to validate our findings, large cohort clinical studies involving numerous pregnant women must be conducted.