A small study indicates that babies born to mothers who were vaccinated against COVID-19 during pregnancy are more likely to have antibodies against the virus in their blood at six months of age than babies born to unvaccinated mothers who were infected while pregnant.
Researchers published a study in JAMA on Monday that included 28 six-month-old infants born to women who were vaccinated with two doses of an mRNA vaccine between 20 and 32 weeks' gestation, when transfer of maternal antibodies to the fetus via the placenta is at its peak, and 12 babies of the same age whose mothers were infected during the same time period.
They discovered detectable levels of immunoglobulin G (IgG), the most common antibody in the blood, in 57 percent of vaccinated mothers' newborns but just 8% of infected, unvaccinated mothers' babies.
Other preliminary research findings, as well as data from the Centers for Disease Control and Prevention, corroborate the new results.
COVID-19 vaccines can also generate a high immune response in pregnant women, who subsequently convey the antibodies to their babies through the placenta and breast milk, according to a 2021 study.
The blood and breast milk of 131 women of reproductive age, including 84 pregnant, 31 breastfeeding, and 16 who were not pregnant, were studied by researchers at Brigham and Women's Hospital and Massachusetts General Hospital and published in the American Journal of Obstetrics and Gynecology.
The women received two doses of either the Pfizer/BioNTech or Moderna vaccine between Dec. 17, 2020 and Mar. 2, 2021.
The scientists found that the vaccine-induced antibody levels were similarly high in all three groups of women.
"COVID vaccination in pregnancy and lactation generated robust humoral immunity similar to that observed in nonpregnant women with similar side effect profiles," the authors said.
According to Live Science, experts suspected vaccines would be safe and beneficial in pregnant and lactating mothers at the time, but they didn't have strong data because these individuals were excluded from trials.
Antibodies aren't the body's main defense mechanism, therefore it's unclear how high they need to be to defend against infection.
However, "many interested parties, from parents to pediatricians, want to know how long maternal antibodies persist in infants after vaccination," according to Dr. Andrea Edlow of Massachusetts General Hospital in Boston.
"We hope these findings will provide further incentive for pregnant people to get vaccinated," the research team behind the new paper concluded.
