Second Doses of COVID-19 mRNA Vaccines Are Important in Pregnancy

The immune system of a pregnant woman maintains a delicate balance: It must tolerate the “foreign” antigens of the fetus while still protecting the mother and fetus from foreign pathogens. Unvaccinated pregnant women who get COVID-19 often develop severe illness, perhaps because their immune response is more tolerant of foreign antigens.

The unusual immunological milieu of pregnancy also could alter the response to vaccines. A multi-institutional team studied response to the Pfizer and Moderna COVID-19 mRNA vaccines in pregnant women, lactating women, and nonpregnant age-matched controls. Following the first dose of these two-dose vaccines, the ability of the antibodies' Fc region to bind to pathogens and to pathogen-infected cells was lower…