Researchers at Massachusetts General Hospital, Brigham and Women’s Hospital, and the Ragon Institute of MGH, MIT, and Harvard examined 131 women who received the Pfizer / BioNTech or Moderna Covid-19 vaccine. Of the participants, 84 were pregnant, 31 breastfeeding and 16 were not pregnant. The samples were taken between December 17, 2020 and March 2, 2021.
Vaccine-induced antibody levels were equivalent in pregnant and lactating women compared to non-pregnant women. Antibody levels were “remarkably higher” than those resulting from coronavirus infection during pregnancy, the team noted.
“These vaccines appear to work incredibly effectively in these women,” said one of the researchers, Galit Alter, professor of medicine at the Ragon Institute.
Additionally, the team found that women pass protective antibodies to their newborns, measured in breast milk and placenta.
Participants used the U.S. Centers for Disease Control and Prevention’s V-safe tool, which allows people who have received a Covid-19 vaccine to track their reaction. Alter said they found no evidence of stronger side effects or more intense side effects in pregnant and breastfeeding women than in the general population.
While the team found similar antibody levels in women vaccinated with both vaccines, Alter said they found higher levels of IgA antibodies in pregnant women who received the Moderna vaccine. She said this particular type of antibody can be transferred to babies more effectively, over a longer period of time.
“There is reason to believe that having higher IgA immunity levels might be more protective,” noted Alter. She said further research on this finding could help inform policy decisions about which vaccines are used for pregnant populations.
Recent research has also revealed that mRNA vaccines produce illicit antibodies in pregnant women that can be transferred to their babies, although this is the largest vaccine study in pregnant women to date. Pregnant and lactating women were not included in the initial clinical trials of the vaccines.
With no data to review to help pregnant women get vaccinated against Covid-19, Alter said researchers and new and expecting mothers – especially healthcare workers – have stepped up to fill the void .
“This is an urgent need because we are not just protecting one person in this vaccination effort, we are protecting two people at the same time,” Alter said.
Keri Enriquez of CNN Health contributed to this report.