Pregnant women gain COVID antibodies from vaccine — and pass them to baby, study finds

Because pregnant and breastfeeding women were left out of initial clinical trials for COVID-19 vaccines, much remains unknown about how safe and effective the shots are for this group.

But now, a new study shows they gain similar levels of antibodies after vaccination than non-pregnant and non-lactating women.

What’s more, these antibodies were also found in the umbilical cord blood and breast milk of every woman included in the study, meaning coronavirus immunity is passed on from mother to baby, according to the study published Thursday in the American Journal of Obstetrics and Gynecology.

The finding offers encouraging news for pregnant and breastfeeding women, who face increased risks for severe COVID-19, including intensive care unit admission, mechanical ventilation and death, as well as dangerous pregnancy outcomes such as preterm birth.

“We now have clear evidence the COVID vaccines can induce immunity that will protect infants. We hope this study will catalyze vaccine developers to recognize the importance of studying pregnant and lactating individuals, and include them in trials,” co-senior author of the study Dr. Galit Alter, a core member of the Ragon Institute at the Massachusetts General Hospital, said in a statement. “The potential for rational vaccine design to drive improved outcomes for mothers and infants is limitless, but developers must realize that pregnancy is a distinct immunological state, where two lives can be saved simultaneously with a powerful vaccine.”

COVID-19 vaccines offer more protection than natural infection

The team of researchers studied 131 women who received either the Pfizer or Moderna coronavirus vaccine; 84 were pregnant, 31 lactating and 16 non-pregnant.

Antibody levels were “equivalent” across all three groups, although levels of antibodies following second doses of the Moderna shot were higher compared to those after the Pfizer vaccine. Side effects were also rare and comparable among all the study participants.

The researchers also found “significantly higher” antibody levels after vaccination compared to those from natural infection.

Dr. Iffath Hoskins, an OB-GYN at NYU Langone Medical Center in New York, told NBC News the study results are “very much reassuring,” given there was debate among the medical community about how well the vaccines would work in pregnant women because their immune system’s are busy supporting the fetus — adding the job of building immunity against a novel virus introduced many unknowns.

“What this study is showing us is that the mother does mount a robust response,” Hoskins, who is also president-elect of the American College of Obstetricians and Gynecologists, told the outlet. “Her body does wake up … making antibodies to the prod that just happened, which is the coronavirus vaccine.”

A separate study published in December found that pregnant women who had COVID-19 didn’t transfer the coronavirus to their babies, despite the virus’s presence in the mother’s respiratory system. The researchers suspected viral transmission was blocked because of the lack of virus particles in the mother’s blood and major proteins the virus uses to enter cells in the placenta.

The study also found that mother-to-newborn transfer of coronavirus antibodies from natural infection was “significantly lower” than the transfer of flu antibodies.

Vaccination is a “personal choice”

The Centers for Disease Control and Prevention says that getting vaccinated against COVID-19 is a “personal choice” for pregnant and breastfeeding women, and that any of the authorized vaccines can be offered to them in the U.S.

Still, experts “believe they are unlikely to pose a specific risk for people who are pregnant” because of how the vaccine works, the CDC said.

The Pfizer and Moderna vaccines pump mRNA, a molecule that is already in your body, directly into muscles. This mRNA carries instructions that teach cells to produce antibodies against the coronavirus.

The vaccines do not inject live (weakened) virus or an inactivated (killed) virus, and therefore cannot give someone COVID-19.

All the contents of the vaccine disappear after a couple of days as cells quickly break down the material, leaving only your immune system’s memory of the shot and its acquired protection against the coronavirus, according to the CDC.