• Posted September 12, 2025

Even Healthy Babies At Risk For Severe RSV Infection

RSV can make even healthy, full-term babies sick enough to land in the hospital or require intensive care, a new study says.

In fact, more than half of RSV-infected infants and children who required intensive care or prolonged hospitalization were born at term and had no chronic health problems, researchers reported Sept. 9 in The Lancet Regional Health-Europe.

RSV is shorthand for respiratory syncytial virus. The findings support recommendations that all newborns be protected against it, either by maternal vaccination during pregnancy or by preventive antibody treatment, researchers said.

“We know that several underlying diseases increase the risk of severe RSV infection, and it is these children who have so far been targeted for protection with the preventive treatment that has been available,” said senior researcher Samuel Rhedin, a resident physician at Sachs’ Children and Youth Hospital in Stockholm, Sweden.

“However, the study highlights that a large proportion of children who require intensive care due to their RSV infection were previously healthy,” Rhedin said in a news release. “Now that better preventive medicines are available, it is, therefore, positive that the definition of risk groups is being broadened to offer protection during the RSV season to previously healthy infants as well.”

Each year in the U.S., an estimated 58,000 to 80,000 children younger than 5 are hospitalized due to RSV, according to the U.S. Centers for Disease Control and Prevention (CDC). The younger the child, the higher the risk for a severe infection.

The CDC recommends that all infants be inoculated against RSV. Pregnant women can get a dose of the vaccine Abrysvo, or babies younger than 8 months can get a dose of either nirsevimab or clesrovimab, both monoclonal antibodies, prior to their first cold-and-flu season.

For the new study, researchers analyzed data from more than 2.3 million children born in Sweden between 2001 and 2022.

More than 1 in 10 (12%) infected with RSV wound up with a severe illness that either caused death or required ICU care or hospitalization for more than a week, results showed.

Underlying health problems were found in about 41% of children admitted to the ICU, nearly 34% of those who spent a week or more in the hospital and 55% of those who died, researchers said.

The median age of children who needed intensive care was just under 2 months, the study says. Among babies 2 months or younger, only 40% had other health problems that raised their risk of severe RSV.

The research team identified several factors that increased a child’s risk of dying or requiring intensive care:

• Children born in the winter had about a tripled risk.

• Babies with a twin or a sibling 3 years of age or younger had triple the risk.

• Children born small at birth had a nearly quadrupled risk.

• Children with underlying health problems had a more than fourfold increased risk.

“When shaping treatment strategies, it is important to take into account that even healthy infants can be severely affected by RSV,” lead researcher Dr. Giulia Dallagiacoma, a physician and doctoral student at the Karolinska Institute in Sweden, said in a news release. “The good news is that there is now preventive treatment that can be given to newborns, and a vaccine that can be given to pregnant women.”

More information

The U.S. Centers for Disease Control and Prevention has more on RSV protection for babies.

SOURCE: Karolinska Institute, news release, Sept. 9, 2025