WASHINGTON, March 8, 2024 (BSS/AFP) - A new treatment for infant respiratory syncytial virus (RSV) -- a leading cause of severe illness in US babies -- is 90 percent effective in preventing hospitalization, health authorities said Thursday.

A study from the Centers for Disease Control and Prevention (CDC) showed that nirsevimab prevented infants from being hospitalized with RSV, which causes bronchiolitis, in nine out of ten cases, the agency said.

The CDC said it recommends the antibody drug for infants under eight months whose mothers did not receive the existing maternal RSV vaccine during pregnancy and who are entering their first RSV season, which runs from October to March in the United States.

Around 58,000 to 80,000 children aged under age five are hospitalized with RSV each year in the United States, according to the CDC, with an estimated 100 to 300 infant deaths.

The study, which followed the cases of 685 babies from October to February, is the first public data on the effectiveness of nirsevimab, which was first introduced in August.

"Results show that nirsevimab was 90% effective at preventing RSV-associated hospitalization in infants during their first RSV season," the CDC said in a statement.

However, the health body noted that it was continuing to review the treatment and that more research was needed to determine its effectiveness over a full RSV season.

A separate measure, a maternal RSV vaccine called abrysvo, is already available in the United States for those in their 32nd through 36th weeks of pregnancy, if that period falls between September and January.