Pregnant women infected with SARS-CoV-2 are at greater risk of hospitalization for COVID-19, admission to the intensive care unit and death than nonpregnant women of reproductive age. Unfortunately, pregnant and lactating women were initially excluded from COVID-19 vaccine trials until a trial of the Pfizer/BioNTech vaccine in pregnant women began in February of this year.

Now that the rollout of the COVID vaccines has begun, scientists are looking to see if mRNA vaccines such as those from Pfizer/BioNTech and Moderna will produce sufficient immunity to SARS-CoV-2 in pregnant or breastfeeding women and give their babies immunity through cord blood or breast milk. The results are promising.

Antibodies detected in cord blood and breast milk indicate that vaccinations given to pregnant women also conferred immunity to their newborns.

Researchers from Brigham and Women’s Hospital, Massachusetts General Hospital and the Ragon Institute found vaccine-induced antibody levels in more than 130 pregnant and lactating women were the same as those in nonpregnant women. Importantly, antibody levels among vaccinated women in all three groups were higher than antibody levels in women who were naturally infected with SARS-CoV-2 during their pregnancy.

The findings fill an important gap and should reassure women that getting vaccinated carries real benefits. Pregnant and lactating women have long been reluctant to participate in clinical trials, presumably for safety concerns, Kathryn Gray, lead author on the study, said. And, unfortunately, that has frequently left women without any data on which to base decisions about medications and therapies, and has often delayed their access to treatment.

Antibodies detected in cord blood and breast milk indicate that vaccinations given to pregnant women also conferred immunity to their newborns, Gray told TheDoctor. The study also shows how eager pregnant and lactating women are to participate in research.

The immune responses of pregnant women were similar to those of nonpregnant women. “We were expecting that, but it was still very encouraging to see,” she said.

The results support the current CDC guidelines that pregnant and lactating women should be eligible to get the vaccine, although women need to weigh the risks and benefits for themselves and with their doctors, said Gray, a maternal-fetal medicine specialist at Brigham and Women’s Hospital, adding, “More pregnant and breastfeeding women will be looking at the evidence and trying to decide whether or not they want to get the vaccine. We are approaching the majority of those conversations because of the way the vaccines have been rolled out.”

Going forward, Gray and her team want to examine how the time between vaccination and delivery affects the number of antibodies detected in the cord blood supplied to an infant. The vaccine had just become available at the time of this study, and doctors had only records on deliveries by women who were vaccinated in their third trimester.

“We would like to see how the level of antibodies detected in the cord blood varies in women vaccinated in their first or second trimester, so we can time vaccine delivery during pregnancy to give optimal benefit to mom and baby,” Gray indicated.

The study is published in the American Journal of Obstetrics and Gynecology.