■ Some research is showing pregnant women may pass on virus resistance to their babies,

Pregnant women who receive a coronavirus vaccine not only acquire protective antibodies against the virus for themselves but also may pass along immunity to their babies, emerging research shows. Several preliminary studies suggest that women who received an MRNA vaccine (Pfizer or Moderna) during pregnancy had COVID19 antibodies in their umbilical cord blood. Another study also detected antibodies in their breastmilk, indicating that at least some immunity could be transferred to babies both before and after birth.

WHY IT MATTERS

Researchers have seen that pregnant women who recover from COVID-19 can pass along their natural immunity to their babies. But the observation that vaccine-induced antibodies may reach a fetus through cord blood and a newborn through breastmilk is a new discovery that may have broader implications in the fight against the virus.

WHAT IT MEANS

Brenna Hughes, vice chair for obstetrics and quality at Duke University, said several recent papers that have not yet been peer-reviewed are “the first to show what we had hoped would be true, which is that these vaccines could be potentially protective through antibodies passed on to the fetus.”

“So worries about possible risk and harm may be proven quite the opposite. In fact, it may be proven that the vaccines actually provide protection to the developing fetus,” said Hughes. She was not involved in the studies.

VACCINES DIFFER

Andrea Edlow, who co-authored the study, said one interesting aspect was that the researchers were able to compare antibody responses between the Moderna and Pfizer vaccines. They found that the women who had received the Moderna vaccine had higher levels of one type of antibody, called IGA. This mucosal antibody is typically found in breastmilk and protects breastfed babies against diseases, such as COVID-19, that attack mucosal areas, particularly the respiratory tract.

“The significance of generating a more robust IGA response is not totally clear,” said Edlow, assistant professor of obstetrics and gynecology at Harvard Medical School. But, she added, “If moms are getting a better IGA boost from the Moderna vaccine, could that somehow translate into improved protection of their baby through breastmilk?”

MOTHERS AT RISK

“Overall, I think the message is good news,” said Denise Jamieson, professor and chair of the department of gynecology and obstetrics at Emory University.

Jamieson, who was not involved in the studies, said “it’s also important to remember that the main reason why we’re so focused on getting pregnant women vaccinated for COVID is because we know the mothers are at increased risk of severe disease.”

WHAT’S NEXT

Edlow said the researchers will soon study the effects of the Johnson & Johnson vaccine. And experts must also determine how effective the infant antibodies are and how long the protection will last.