A new RSV drug designed to protect young children was 93% effective in preventing hospitalization for the viral illness, a new study reports. In addition, the drug was 89% effective in preventing all types of doctor visits for RSV, short for \”respiratory syncytial virus.\”
The new research, published Monday (Dec. 9) in the journal JAMA Pediatrics, focused on a drug approved in 2023, niresevimab (Befortus). This drug, given as an injection, uses antibodies made in a laboratory to block RSV from getting into cells. Unlike a vaccine, niresevimab does not teach the body to make its own antibodies; rather, it provides a ready supply.
The new study results show that niresevimab is very effective in preventing young children from needing to be hospitalized for RSV, as well as other lesser degrees of medical care, such as outpatient visits. However, the study authors pointed out that \”only a small fraction\” of the infants in the study who were eligible for the drug actually received nirasevimab.
Ultimately, the findings suggest that if the drug is used more widely, nirasevimab could have a \”substantial public health impact\” in future RSV seasons, they concluded.
Prior to nirasevimab\’s approval in 2023, there was no comprehensive strategy for preventing RSV in infants, for whom the virus is the leading cause of hospitalization.
Each year in the United States, 2 to 3 of every 100 infants younger than 6 months are hospitalized for RSV, according to the Centers for Disease Control and Prevention (CDC). These cases start out mild, causing a runny nose and cough, but then progress to inflammation and infection in the lungs. Children hospitalized for RSV often require supplemental oxygen and IV fluids, as well as breathing assistance from a ventilator.
To see how well nirasevimab is working in the real world, the study authors compared the three RSV seasons before the drug\’s approval to the 2023-2024 season after its approval. The three pre-approval seasons spanned from 2017 to 2020, before the pandemic, which disrupted the normal pattern of RSV spread.
The drug is currently recommended for all infants younger than 8 months whose mothers have not received a maternal vaccine against RSV. (If a person gets vaccinated during pregnancy, the resulting antibodies are passed to the fetus before birth.)
The CDC recommends that eligible infants be given nirasevimab just before the start of their first RSV season — around October — or within a week of birth if they are born between October and March. Select older children are also advised to take the drug before their second RSV season.
Overall, the new study included data from about 28,700 children under age 5 who needed medical care for respiratory infections during RSV season. The children were treated at seven academic pediatric centers, and required varying levels of care, including outpatient doctor visits and hospitalizations.
Of the children, about 7,500 were treated for RSV, and 4,500 of those were hospitalized for the infection. The remaining children, who tested negative for RSV, served as a point of comparison for the study\’s analysis.
The study found that RSV accounted for a similar proportion of respiratory-infection-related medical visits before and after nirasevimab\’s approval. Looking at the 2023-2024 season, the researchers found that the number of infants who received niresvimab was lower: 402 received the newer drug, while 16 received an older drug called palivizumab (Synagis), which is only recommended for some children.
\”Only a small fraction of infants received niresvimab in their first RSV season,\” the authors wrote. An additional 70 infants were born to mothers who had received a maternal RSV vaccine. The researchers plan to study the vaccine\’s real-world effectiveness, but said they would need more data to do so.
The authors noted that there may be several reasons why use of both niresvimab and the vaccine may have been lower in 2023. For example, there were supply issues with niresvimab during the 2023-2024 season. In addition, the RSV season started unusually early in 2023, and the maternal vaccine did not become available until nearly the same time.
Despite the study\’s limitations, the research and other work collectively suggest that nirasevimab has the potential to substantially reduce the likelihood of infant RSV hospitalizations — if and when it becomes more widely used.