Washington, D.C. — Moderna’s updated 2024-25 COVID-19 vaccine offers significant, though waning, protection against illness and hospitalization, according to a large new study. The vaccine was 39% effective at preventing medically attended illness among adults and 53% effective against hospitalization, particularly for those at higher risk.
Boosters Still Matter: New Data on 2024-25 COVID Vaccine
A new observational study confirms the continued benefit of annual COVID-19 vaccination, even as the virus evolves.
- The updated Moderna vaccine (mRNA-1273) targets the Omicron KP.2 variant.
- Vaccine effectiveness against hospitalization was 52.8% after a median of 55 days.
- Protection remained significant even after four months, at 45.2% against hospitalization and 33.1% against illness.
- Over 70% of participants had received a 2023-24 mRNA vaccine, highlighting the additive effect of yearly boosters.
Q: How effective is the new Moderna COVID vaccine?
A: The study found the 2024-25 Moderna vaccine was 39% effective at preventing COVID-19 illness requiring medical care and 53% effective at preventing hospitalization, offering substantial protection, especially for vulnerable populations.
The observational study, published late last week in Infectious Diseases and Therapy, analyzed data from 596,248 adults who received the updated mRNA-1273 vaccine between August 2024 and April 2025. Researchers matched each vaccinated individual with an unvaccinated counterpart to compare outcomes.
Overall, vaccine effectiveness (VE) against COVID-19-related hospitalization was estimated at 52.8% after a median follow-up of 55 days. Protection against illness requiring medical attention reached 39.4% over the same period. As time passed, VE against hospitalization decreased slightly but remained substantial at 45.2% during an extended follow-up. Protection against illness needing medical attention was 33.1% after a median of 127 days (approximately four months).
Researchers observed consistent protection across various subgroups, including older adults and individuals with pre-existing medical conditions. “Protection was consistently observed across subgroups, including older adults and those with other specific underlying medical conditions that may increase the risk of severe COVID-19,” the authors wrote.
Incremental Benefit of Annual Vaccination
Because more than 70% of the study participants had already received a 2023-24 mRNA-1273 vaccine, the findings underscore the additional protection provided by the 2024-25 vaccine. This suggests that staying up-to-date with annual boosters is crucial for maintaining immunity.
“As COVID-19 vaccination uptake remains low, it is imperative to communicate the additive protection COVID-19 vaccine provide year after year to reinforce confidence in vaccination among clinicians and the general population,” the researchers emphasized.
It’s important to note that this was an observational study, meaning participants weren’t randomly assigned to receive the vaccine. This introduces the possibility that differences between the vaccinated and unvaccinated groups could have influenced the results. For example, vaccinated individuals might have generally been healthier or practiced more preventative behaviors.
To account for these potential confounding factors, the researchers employed multiple analytical approaches and carefully matched vaccinated and unvaccinated adults based on key characteristics, including age, sex, race, geographic location, prior vaccination status, and previous healthcare utilization.
“The updated 2024–2025 mRNA-1273 KP.2 vaccine demonstrated substantial and incremental protection against hospitalization and medically-attended COVID-19 during the 2024/2025 respiratory virus season in the US,” the authors concluded. “These findings support continued annual vaccination efforts to reduce the burden of COVID-19, particularly among older adults and high-risk populations.”
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