4 noviembre, 2021

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

Although pregnancy blunted response to the first dose, that deficiency resolved after the second dose.

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 in both pregnant and lactating women, compared with responses in nonpregnant women. However, following the second dose, this deficiency resolved — in both blood and breast milk of the lactating women.


This study emphasizes the importance of making sure pregnant women receive their second doses of mRNA vaccines for COVID-19, because the binding ability of the antibody Fc region is important to the innate immune response. Although this study did not report clinical outcomes directly, other studies have shown that clinical responses after two doses are superior to responses after one dose.

Créditos: Comité científico Covid

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