Babies under 6 months old still have one of the highest rates of hospitalization from COVID-19 infections compared to other age groups, but no COVID vaccine is available for these infants.
That's one reason the American College of Obstetricians and Gynecologists, or ACOG, recommends COVID vaccination during pregnancy.
"There are a number of studies that show one of the benefits of COVID vaccination during pregnancy is the passage of antibodies to the newborn, and then that protects the newborn against COVID," says Dr. Kevin Ault, a professor of obstetrics and gynecology at Western Michigan University Homer Stryker M.D. School of Medicine in Kalamazoo, Mich.
ACOG reaffirmed that guidance last week, and a new study of more than 140,000 infants further confirms the protection that COVID vaccination during pregnancy offers babies in their first few months of life. The journal Pediatrics published the study Friday.
The research also shows that the vaccine does not increase the risk of other infections in children whose mothers got the COVID shot during pregnancy, contradicting claims by at least one member of the vaccine policy committee appointed by Secretary of Health Robert F. Kennedy, Jr.
"There is often an increased risk for a subsequent infection after a viral infection, such as an increased risk of pneumonia after influenza infection, so we wanted to study whether protection against COVID-19 could influence the risk of other infections as well," Dr. Helena Niemi Eide, the study's lead author, from the University of Oslo in Norway, says. "But we found that COVID vaccination in pregnancy protected the infant against COVID and had no apparent effect on other infections."
Back in 2021 to 2023, the period of time covered by the new study, "people would ask us, should we vaccinate pregnant women?" says Dr. Thomas Nguyen, a pediatrician in northeast Ohio and an associate professor at Ohio University's Heritage College of Osteopathic Medicine in Athens. The data had become clear by then that pregnancy increased the risk of hospitalization and needing a ventilator from COVID, leading ACOG and other leading medical organizations to recommend COVID vaccination during pregnancy.
"Because the recommendations from those organizations were so strong, we said yes," Nguyen says. "This study basically confirms that we were correct in making those recommendations, so it's good to see our expectations were met with respect to COVID vaccines protecting young infants before they were old enough to get vaccinated themselves."
U.S. infants under 6 months old have COVID hospitalization rates as high as those in people who are 65 to 74 years old, according to a study from September 2024. About one in five babies hospitalized with COVID were admitted to the ICU, that research found. Other studies have also supported the safety of receiving the COVID vaccine during pregnancy.
In this new study, researchers in Norway tracked 146,031 children born between March 2020 and December 2023 and looked at their medical records for up to two years after birth. The mothers of one in four of those children received the COVID vaccine while pregnant.
Babies exposed to the vaccine before birth were no more likely to visit the hospital for overall infections (of any kind) than those whose mothers did not get vaccinated in pregnancy. However, infants whose mothers were vaccinated were about half as likely to visit the hospital specifically for COVID in their first two months of life compared to babies not exposed to the vaccine in utero.
When babies were 3 to 5 months old, the risk of a hospital visit for COVID was 24% lower in those exposed to the vaccine, but the vaccine's protection against COVID wore off by the time infants were older than 6 months.
The researchers also looked at children's visits to primary care. Babies whose mothers were vaccinated were about 5% more likely to see a doctor for an infection, but further analysis of the data suggested that the increase had more to do with different behaviors of mothers who got the vaccine compared to those who didn't.
"If you're more likely to get vaccinated during pregnancy, you're probably more likely to take your newborn to the doctor to be checked out for those kinds of illnesses," Ault says. "There's not really a biological mechanism to explain those findings," otherwise, he says.
In Norway, there is no cost associated with doctor visits or immunizations. Differences in how often vaccinated people versus unvaccinated people visit health care professionals are a common complicating factor that affects vaccine studies, explains Niemi Eide. "We therefore tried to restrict the analysis to women with similar health seeking behavior to see if that influenced the results," she says. Other research has also found different health-related behaviors in people who get the COVID vaccine compared to those who don't, namely that those who get vaccinated are more likely to visit the doctor in general.
Nguyen says this study is particularly reassuring because it includes so many children, which is easier for European countries with single-payer health care systems to do than the U.S. since they can track patients more easily.
The findings are also helpful, Nguyen says, in rebutting claims made by Robert Malone, who Kennedy appointed as chair of the CDC committee that makes vaccine policy for the country. A federal judge ruled last week that Malone's role on the committee, like those of other members appointed last year, is not legally valid because Kennedy did not appear to follow federal law when he replaced the members he dismissed from the committee.
Malone has repeatedly claimed, without evidence, that "immune dysregulation" can result from the vaccine and cause more infections in those exposed to it. If that were true, this study would have found a higher risk of infection in babies whose mothers got the vaccine during pregnancy, Nguyen says. Since the researchers found no increased risk of overall infections, "the findings of this paper refute the whole idea of that being a problem," he says.
The study was funded by the University of Oslo and a Scandinavian government agency with no funding from pharmaceutical companies. It's part of a larger research collaboration with several studies on Covid vaccination during pregnancy, Niemi Eide says.
Tara Haelle is an independent health and science journalist and author of Vaccination Investigation and The Informed Parent.
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