Babies get Covid-19 antibodies from mothers while in the womb, study finds

Antibodies that protect against the coronavirus often get transferred from mother to infant during pregnancy — a finding that indicates a mother passes along at least some protection to her child, researchers reported Friday.

The findings also suggest that vaccinating pregnant women might protect their unborn babies, as well, the researchers said — and it’s worth studying the possibility. Pregnant women are advised to get influenza vaccines to protect both themselves and their babies.

Newborn specialist Dr. Dustin Flannery of Children’s Hospital of Philadelphia and colleagues studied more than 1,400 mothers and newborns. They found that protective IgG antibodies were transferred across the placenta in 72 out of 83 infected or previously infected pregnant women they studied.

“Our findings demonstrate the potential for maternally derived SARS-CoV-2 specific antibodies to provide neonatal protection from coronavirus disease 2019,” the team wrote in the Journal of the American Medical Association’s JAMA Pediatrics.

None of the babies of infected mothers developed coronavirus infection. And 60% of the women who had antibodies to coronavirus had no symptoms, the researchers reported.

“Could maternal antibodies help delay the onset of infection or protect the infant from becoming infected, having severe disease, or dying of COVID-19?” asked Dr. Flor Munoz, a molecular virologist at the Baylor College of Medicine, who was not involved in the research.

Newborns are vulnerable to infection, and any protection would be welcome, Munoz wrote in an accompanying commentary. But it’s also known that antibodies against other viruses, such as influenza or tetanus, wear off quickly when passed from mother to infant during pregnancy, so it would be important to study when and how to vaccinate infants, Munoz said.

The US Centers for Disease Control and Prevention recommends immunizing babies against the flu at six months, for instance, even if the mothers were vaccinated during pregnancy.

“To what extent can antibodies transferred through breast milk protect lactating newborns?” Munoz asked.

“Should infants be vaccinated regardless of maternal infection, and if so, what is the best timing to initiate infant vaccines? Is there a potential detrimental effect of maternal antibodies on infant responses to active immunization? And what would be the optimal vaccine and vaccination regimen for infants, considering their risk and unique immunologic needs?”