Study finds pregnant, lactating women protected by COVID-19 vaccines, pass antibodies to newborns

The largest study of its kind to date found that the Pfizer-BioNTech and Moderna COVID-19 vaccines provide "robust" immunity for pregnant and lactating women, who can also pass protective vaccine-generated antibodies to newborns.

The initial COVID-19 vaccine trials did not include data on pregnant and lactating women. And while the overall risk for severe illness is low, pregnant women with COVID-19 are more likely to become severely ill and may be at increased risk for poor outcomes, such as preterm birth, according to the U.S. Centers for Disease Control and Prevention.

The new research, published Thursday in the American Journal of Obstetrics and Gynecology, looked at 131 women who either received the Pfizer-BioNTech or Moderna COVID-19 vaccine. Among the participants, 84 were pregnant, 31 were lactating and 16 were not pregnant. Samples were taken between Dec. 17, 2020 and March 2, 2021.

The study found that the vaccines generated "robust humoral immunity in pregnant and lactating women," and the immune response generated by the shots was similar to that observed in the women who weren’t pregnant. 

Perinatal Center of Tatarstan's Republican Clinical Hospital in Kazan

FILE - A pregnant patient receives an ultrasound during the COVID-19 pandemic in an undated file image. (Photo by Yegor AleyevTASS via Getty Images)

The team also compared vaccine-induced antibody levels to those induced by natural COVID-19 infection during pregnancy and found significantly higher levels of antibodies from vaccination.

Regarding infants, the research found that vaccine-generated antibodies were also present in all umbilical cord blood and breast milk samples taken — showing the transfer of antibodies from mothers to newborns.

"We now have clear evidence the COVID vaccines can induce immunity that will protect infants," said Galit Alter with the Ragon Institute and co-senior author of the study. "We hope this study will catalyze vaccine developers to recognize the importance of studying pregnant and lactating individuals, and include them in trials."

The study was done by researchers at Massachusetts General Hospital (MGH), Brigham and Women’s Hospital and the Ragon Institute of MGH, MIT and Harvard.

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The study also offered insight into potential differences between the immune response from the Pfizer vaccine compared to the Moderna vaccine. 

While the study found comparable levels of antibodies in women from both shots, researchers noted that the levels of mucosal (IgA) antibodies were higher after the second dose of Moderna compared to the second dose of Pfizer. 

IgA is a predominant antibody in breast milk.

"This finding is important for all individuals, since SARS-CoV-2 is acquired through mucosal surfaces like the nose, mouth and eyes," said Kathryn Gray, an obstetrician at Brigham and Women’s Hospital and a first author of the paper. "But it also holds special importance for pregnant and lactating women because IgA is a key antibody present in breast milk."

Participants in the study used the CDC’s V-safe tool on smartphones, which allows people who have received their COVID-19 vaccine to report any side effects after getting inoculated. Side effects after vaccination were rare and also comparable across all three groups, the authors noted.

Andrea Edlow, a maternal-fetal medicine specialist at MGH and co-senior author of the study, called the research "very encouraging for pregnant and breastfeeding women, who were left out of the initial COVID-19 vaccine trials."

"Filling in the information gaps with real data is key — especially for our pregnant patients who are at greater risk for complications from COVID-19," Edlow added.

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This story was reported from Cincinnati.