Sydney Nobles

Introduction The Severe Acute Respiratory Syndrome Corona Virus 2, or SARS-CoV-2, is transmitted via nasal passages by respiratory droplets, and infects pulmonary cells by binding to their angiotensin- converting enzyme 2 (ACE2) and transmembrane serine protease 2 (TMPRSS2) receptors¹. Spike protein is the specific glycoprotein on the virus that mediates entry into host cell binding ACE2 and TMPRSS2². Type II Alveolar Cells, the cells found in the lung that secrete pulmonary surfactant, seem to be a main cell target, or tropism of SARS-CoV-2². Two vaccines against SARS-CoV-2 were authorized by the FDA for emergency use in December of 2020. As of May 23, 2021, 1.65 billion doses have been distributed worldwide, with 284 million of those doses being distributed in the United States³. Methods A study investigated levels of ACE2 and TMPRSS2 placental tissue throughout gestation⁴. Another study measured maternal serum and cord blood for SARS-CoV-2 anti-spike and anti-receptor binding domain immunoglobulins in both post vaccination and post natural SARS-CoV-2 infection⁵. SARS-CoV-2 immunoglobulins were also measured in breastmilk of lactating women¹. Results Statically significant (p < 0.0011) increases were seen in SARS-CoV-2 antibodies in vaccinated pregnant women compared to naturally infected pregnant women¹. The placental transfer ratio of anti-Spike IgG and anti-Receptor Binding Domain specific IgG were 0.44 and 0.24, respectivly⁵. Levels of vaccine mediated IgA SARS-Cov-2 antibodies in breastmilk were lower in a vaccine response compared to natural infections¹. Conclusions Studies have found that the SARS-CoV-2 vaccine elicits a higher antibody response than a natural infection, which is important since fetal levels of maternally derived SARS-CoV-2 antibodies are directly correlated to the maternal levels¹. However, the placental transfer ratio was found to be lower than other standard gestational vaccines⁵. This suggests that there is an optimal time for the vaccination during gestation, to maximize the placental transfer ratio⁵. IgG SARS-Cov-2 antibodies were the predominant antibody seen in breastmilk in lactating women after the COVID-19 vaccine, whereas IgA SARS-Cov-2 antibodies are predominant in breastmilk after a natural infectiong¹. This difference is thought to be due to a natural infection eliciting a mucosal initiated immune response due to the virus being transmitted through droplets while the vaccine elicits an intramuscular initiated immune response¹.

1. Gray KJ, Bordt EA, Atyeo C, et al. COVID-19 vaccine response in pregnant and lactating women: a cohort study. Am J Obstet Gynecol. Published online March 26, 2021. doi:10.1016/j.ajog.2021.03.023
2. Fenizia C, Biasin M, Cetin I, et al. Analysis of SARS-CoV-2 vertical transmission during pregnancy. Nat Commun. 2020;11(1):5128. doi:10.1038/s41467-020-18933-4
3. COVID Data Tracker. Centers for Disease Control and Prevention. Published March 28, 2020. Accessed March 2, 2021. https://covid.cdc.gov/covid-data-tracker
4. Wastnedge EAN, Reynolds RM, van Boeckel SR, et al. Pregnancy and COVID-19. Physiol Rev. 2021;101(1):303-318. doi:10.1152/physrev.00024.2020
5. Shen C, Xu H, Liu D, Veazey RS, Wang X. Development of serum antibodies during early infancy in rhesus macaques: implications for humoral immune responses to vaccination at birth. Vaccine. 2014;32(41):5337-5342. doi:10.1016/j.vaccine.2014.07.036