Antibodies that guard against Covid-19 can transfer from mothers to babies while in the womb, say researchers indicating that vaccinating mother-to-be may also have benefits for their newborns.
The study showed that, among the participants, the vast majority of the babies born to women - 78 percent - had detectable antibodies in their umbilical cord blood.
There was no evidence that any of the infants had been directly infected with the virus and all were Covid-19 negative at the time of birth, further indicating that the antibodies had crossed the placenta - the organ that provides oxygen and nutrients to a growing baby during pregnancy - into the fetal bloodstream, the researchers said.
"Since we can now say that the antibodies pregnant women make against Covid-19 have been shown to be passed down to their babies, we suspect that there's a good chance they could pass down the antibodies the body makes after being vaccinated as well," said researcher Yawei Jenny Yang from the Cornell University.
For the study, published in the American Journal of Obstetrics and Gynecology, the team analyzed blood samples from 88 women who gave birth between March and May 2020 in the US.
All of the women had Covid-19 antibodies in their blood, indicating that they had contracted the virus at some point even though 58 per cent of those women had no symptoms.
Furthermore, while antibodies were detected in both symptomatic and asymptomatic women, the researchers observed that the concentration of antibodies was significantly higher in symptomatic women.
The team also found that the general pattern of antibody response was similar to the response seen in other patients, confirming that pregnant women have the same kind of immune response to the virus as the larger patient population -- something that hadn't previously been known for sure since a woman's immune system changes throughout pregnancy.
This data implies that pregnant women could pass along vaccine-generated antibodies in the same way, potentially shielding both mother and child from future infection. However, it is not yet known exactly how protective these antibodies might be, or how long that protection might last, they added.