Mothers who get vaccinated against Covid-19 while pregnant likely protect their babies from hospitalization due to the virus when they are born, according to the Centers for Disease Control and Prevention.
Babies younger than 6 months old were 61% less likely to be hospitalized with Covid if their mothers received Pfizer or Moderna's two-dose vaccine during pregnancy, a study published Tuesday in the CDC's Morbidity and Mortality Weekly Report found.
Maternal vaccination later in pregnancy, 21 weeks to 14 days before delivery, was associated with an even higher level of protection, 80%, for the baby against Covid hospitalization.
Dr. Dana Meaney-Delman, head of the CDC's infant outcomes branch, said the study suggests antibodies transferred from the mother to her developing fetus protect the newborn against Covid.
"Unfortunately, vaccination of infants younger than 6 months old is not currently on the horizon, highlighting why vaccination during pregnancy is so important for these young infants," Meaney-Delman told reporters during a conference call on Tuesday.
Previous research, published in the American Journal of Obstetrics and Gynecology, had found the mother's antibodies from the Covid vaccine are transferred across the placenta to the developing fetus. The CDC study provides some real-world evidence that the antibodies are protective in newborn infants.
The overwhelming majority of infants, 84%, hospitalized with Covid in the study were born to unvaccinated mothers. The study examined 379 infants across 20 children's hospitals in 17 states from July through January. The infants were split between two groups, 176 who had Covid and 203 who didn't have it. Sixteen percent of the Covid positive infants' mothers were fully vaccinated while, 32% of the Covid negative infants' mothers were fully vaccinated.
The CDC said the study had some limitations. It did not test if the mothers were Covid positive or negative before or during pregnancy, nor did it look at vaccine effectiveness against specific variants. It's also unclear if other differences in behavior between vaccinated and unvaccinated mothers contributed to the risk of infection for their newborns.
The CDC recommends women who are pregnant, planning to get pregnant or breastfeeding should get vaccinated against Covid. People who are currently or recently pregnant are at a higher risk of severe illness from Covid, according to the CDC.