Maternal COVID-19 vaccine antibody response and passage into cord blood.

Prabhu M, Murphy EA, Sukhu AC, Yee J, Singh S, Eng D, et al. Antibody Response to Coronavirus Disease 2019 (COVID-19) Messenger RNA Vaccination in Pregnant Women and Transplacental Passage Into Cord Blood. Obstet Gynecol 2021. https://doi.org/10.1097/AOG.0000000000004438

Question

What is the timing of maternal antibody response and passage to the baby (cord blood)?

Design

Case series.

Setting

New York-Presbyterian Hospital/Weill Cornell Medical Center, New York.

Participants

122 pregnant women with cord blood available at the time of birth who reported receiving 1 or both mRNA–based COVID-19 vaccines and gave birth to a singleton neonate.

Intervention

Semi-quantitative testing for antibodies against S-receptor binding domain was performed on leftover clinical sera of maternal peripheral blood to identify antibodies mounted against the vaccine, but who tested negative for antibodies against the nucleocapsid protein antigen (found following COVID-19 infection).

Outcomes

Passive COVID-19 antibodies.

Main Results

By the time of delivery, 55 pregnant women had received 1 dose of an mRNA vaccine and 67 had received both vaccine doses. All women (who were at least 4 weeks after vaccine dose 1) and cord blood samples, except for 1, had detectable IgG antibodies. 54% and 99% of cord blood samples had detectable IgG from women who received only 1 vaccine dose vs both vaccine doses, respectively. The earliest maternal and cord-blood IgG detection was 5 days and 16 days after the first dose, respectively, and increased over the following number of weeks.

Conclusions

These results shed light on possible vaccination strategies for pregnant women.

Commentary

When mRNA COVID-19 vaccines received emergency use authorization, no studies had been conducted in pregnancy. This important study by Prabhu et al was one of the first to delineate the effects of vaccine timing on maternal and neonatal SARS-CoV-2 IgG levels. Although maternal and neonatal IgG can be detected as early as 1-2 weeks following vaccine dose 1, more than one-half of neonates do not have detectable IgG until after maternal vaccine dose 2 and titers continue to increase with time since maternal vaccination. Thus, to optimize neonatal immune protection, both vaccine doses should be administered in pregnancy prior to delivery. As study participants were all in the 3rd trimester at the time of vaccination, further data are needed to understand the effects of vaccine administration earlier in pregnancy on placenta-mediated IgG transfer to the neonate. Taken together with other recent work on COVID-19 vaccination in pregnancy, , as well as the CDC VSafe Pregnancy Registry data, substantial evidence is now available on the efficacy and safety of the mRNA COVID-19 vaccines in pregnancy. Given that both pregnant individuals and neonates are at higher risk for severe COVID-19, vaccination is an important tool for protection of these vulnerable populations.