Caroline Keefer

Introduction: SARS-CoV-2 is the virus responsible for the COVID-19 pandemic. As of May 9, 2022, more than 500 million people have been infected, and more than six million people have died.¹ In this study, IgG and IgA transmission was investigated, studying its role in conferring immunity to fetuses and infants after natural infection, vaccination, and during breastfeeding. One of the main concerns at the beginning of the pandemic was how pregnant people and fetuses would be affected, so this research topic is significant. The purpose of this study was to determine what the safest and most efficient mode of antibody transfer was for fetuses and infants, since they cannot currently be vaccinated against SARS-CoV-2. Risks of COVID-19 disease during pregnancy include greater instances of stillbirth, pre-eclampsia, placental inflammation, preterm delivery, and maternal and neonatal mortality.²  Methods: Antibodies are commonly passed from mother to fetus via endosomal transmission across the placenta,³ so it was important to compare cord blood samples to their maternal counterpart.^4,5 Researchers analyzed blood samples in maternal-fetal and maternal-infant dyads before and after infection, vaccination, and during breastfeeding.^4,6 Enzyme-linked immunosorbent assay (ELISA) was utilized to analyze antibody titers.⁴ Researchers also investigated whether COVID-19 is transferred vertically by testing cord blood and breastmilk for SARS-CoV-2.^2,5 Results: Vertical transmission of SARS-CoV-2 is rare, and this was determined by analyzing cord blood samples.⁵ After infection, IgG was elevated in dyad samples, with statically significant p-values for levels in maternal blood and cord blood samples.⁵ However, some researchers found compromised antibody transfer during infection.³ Vaccination also leads to elevated levels of anti-spike protein IgG antibodies in maternal and cord blood, with p-values less than 0.001.⁴ Mothers who were vaccinated with an mRNA vaccine between 20 and 32 weeks of pregnancy showed higher levels of IgG in their blood post-vaccination compared to naturally infected mothers.⁴ After mRNA vaccination, breastmilk elicited IgG and IgA neutralization capabilities.⁶ Researchers also found that at six months of age, infants of vaccinated mothers had higher levels of anti-spike protein IgG in their blood.⁴ Conclusion: SARS-CoV-2 infection during pregnancy will provide IgG protection, but not as effectively as vaccination.⁴ Due to the risks that come with natural infection during pregnancy,² vaccination is the safer option for pregnant people to confer immunity to their child. It can also be concluded that it is beneficial to breastfeed after COVID-19 vaccination, as IgG and IgA are transferred via breastmilk.⁶

1. WHO Coronavirus (COVID-19) Dashboard. https://covid19.who.int/ Accessed May 9, 2022.
2. Male, V. SARS-CoV-2 infection and COVID-19 vaccination in pregnancy. Nat Rev Immunol22, 277–282 (2022). https://doi.org/10.1038/s41577-022-00703-6
3. Atyeo C, Pullen KM, Bordt EA, et al. Compromised SARS-CoV-2-specific placental antibody transfer. Cell. 2021;184(3):628-642.e10. doi:10.1016/j.cell.2020.12.027
4. Shook LL, Atyeo CG, Yonker LM, et al. Durability of Anti-Spike Antibodies in Infants After Maternal COVID-19 Vaccination or Natural Infection. JAMA. 2022;327(11):1087–1089. doi:10.1001/jama.2022.1206
5. Garcia-Flores, V., Romero, R., Xu, Y. et al. Maternal-fetal immune responses in pregnant women infected with SARS-CoV-2. Nat Commun 13, 320 (2022). https://doi.org/10.1038/s41467-021-27745-z
6. Rosenberg-Friedman, M., Kigel, A., Bahar, Y. et al. BNT162b2 mRNA vaccine elicited antibody response in blood and milk of breastfeeding women. Nat Commun 12, 6222 (2021). https://doi.org/10.1038/s41467-021-26507-1