A large observational study using US healthcare claims and electronic health record data suggests that Moderna’s updated 2024-25 COVID vaccine was 39% effective at preventing medically attended illness among adults and 53% effective against hospitalization, particularly those at high risk for severe disease.

The study, led by scientists from the vaccine manufacturer and published late last week in Infectious Diseases and Therapy, analyzed outcomes among 596,248 adults who received the updated mRNA-1273 vaccine, which targeted the Omicron KP.2 variant, from August 2024 to April 2025. Vaccinated people were matched 1:1 with unvaccinated counterparts.