(The Hill) — The RSV preventive shot for infants approved last year was 90% effective at preventing hospitalizations, according to an analysis released by the Centers for Disease Control and Prevention.

The CDC’s early analysis published Thursday looked at RSV-associated hospitalizations among infants experiencing their first RSV season. Among the nearly 700 infants hospitalized with acute respiratory illness, only 8% had received the RSV monoclonal antibody shot nirsevimab — known commercially as Beyfortus — more than seven days beforehand.

Based on the verified receipt of immunization status among the infants, the analysis determined Beyfortus was 90% effective at preventing RSV-associated hospitalization.

“This early effectiveness estimate supports existing recommendations for the prevention of severe RSV disease in infants in their first RSV season,” the CDC’s analysis stated.

Some limitations cited in the analysis included the relatively small number of infants hospitalized with acute respiratory illness who had received the shot due to delayed availability. And many infants may have contracted RSV before the shot became available, after RSV season had begun.

In July, the Food and Drug Administration approved Beyfortus for preventing RSV in infants. Despite widespread anticipation for the shot, U.S. health officials advised providers to reserve the injection for infants at the highest risk of severe disease due to a short supply and higher than expected demand.

The analysis acknowledged that infants who received the shot were more likely to have underlying conditions.

According to the CDC, only about 41% of females with an infant under 8 months of age reported that their child had gotten the shot as of January.

Last month, Beyfortus manufacturers Sanofi and AstraZeneca announced a reservation program to help ensure readiness for the 2024-25 RSV season.