Transmission of Anti-SARS-CoV-2 IgG Antibodies to Newborns by Vaccination of Pregnant Women

Background and Aims: Vaccination in pregnant women is already performed for viruses and bacteria, which has advantages for the mother and the newborn. Besides a general rejection of COVID-19 vaccines in this population, these are considered safe, effective and may prevent severe disease in pregnant women. Neutralizing antibodies titer measured in vaccinated pregnant is highly predictive of immune protection and can have a protective effect on the newborn. This study aimed to confirm the transfer of the antibodies across the placenta and to test if other factors impact the antibodies titer in the newborn circulation.

Study design and methods: We collected 24 samples of umbilical cord blood from women vaccinated during pregnancy or in the three months before pregnancy and analyzed the data of those pregnancies.

Place and Duration of Study: This cohort study was developed in our hospital between March 2021 and May 2022.

Results: This study confirms the passage of anti-Spike antibodies to the newborn. When comparing the IgG anti-S titers with the timing of vaccination, the analysis suggests that vaccination during the second or third trimester of pregnancy is more effective than before or in early pregnancy (p=0,005). As for the vaccine used (p=0,23) and the mode of delivery (p=0,48), there were no statistical differences.

Conclusion: We suggest the passage of antibodies during the pregnancy, which appears to be more effective during the second and third trimester of gestation. Despite lack of evidence for how long and how effectively this passive immunity can protect the neonate from infection, vaccination of pregnant women should be considered.