An mRNA RSV vaccine was linked to fewer RSV hospital stays in veterans 50 and older
Infections and vaccines after 50Part of a story we are following · 9 articles · See every update
The mRNA-1345 RSV vaccine had an estimated effectiveness of 81.8% against RSV hospitalization in one season in US veterans 50 and older, with lower protection in the oldest group, in a study published Oct. 1, 2026, in JAMA Network Open. It adds real-world data on vaccines against these infections.
RSV, or respiratory syncytial virus, is often thought of as a children’s illness, but it also sends many older adults to the hospital each winter. Several RSV vaccines are now available for adults, including mRNA-1345, which uses the same mRNA technology as some COVID vaccines.
What did the study do?
Researchers used health records from the Veterans Health Administration in the US. Veterans 50 years and older who got a single dose of mRNA-1345 between October 1, 2025, and January 31, 2026, were matched with similar unvaccinated veterans. They were followed for up to 24 weeks, into May 2026. This design, called target trial emulation, tries to mimic a randomized trial using real-world data. The median age was 73.0 years and 91.3% were men.
What did the study find about infections?
| Any documented infection | 60.3% |
|---|---|
| Emergency or urgent care | 60.2% |
| Hospitalization | 81.8% |
| 50 to 59 | 82.9% |
|---|---|
| 80 or older (uncertain) | 28.6% |
Protection against infection fell with age: from 82.9% in people aged 50 to 59 to 28.6% in those 80 or older, and the latter result was uncertain. When vaccinated people who also got a flu shot the same day were compared with people who got only the flu shot, estimates were similar or higher.
Why does this matter?
Trials showed the vaccine works; this study suggests it also protects in a broad, older population, especially against hospital stays. The weaker result in people 80 and older is worth watching, since they are at the highest risk.
How solid is this evidence?
It’s moderate. Mongevity rates it C on our A-to-E scale: a large, well-designed observational study, but not randomized, so differences between vaccinated and unvaccinated people may remain. It covered one season, mostly men, and didn’t compare against other RSV vaccines.
What does this mean for you?
If you’re 50 or older, or caring for someone who is, ask your doctor or pharmacist whether an RSV vaccine is recommended for you this season and which one. Getting it along with your flu shot is an option.
How do I explain this at dinner?
RSV isn’t just a kids’ virus; it lands many older adults in the hospital. A large study of US veterans found that one shot of an mRNA RSV vaccine was linked to far fewer RSV hospital stays during the season, though protection was weaker in the oldest group. A good question for the table: who here is due for an RSV shot?
In one sentence: in veterans 50 and older, the mRNA-1345 RSV vaccine was linked to strong protection against RSV hospitalization in one season, with less protection after 80.
Questions and answers
- What is mRNA-1345?
- An mRNA vaccine against respiratory syncytial virus for adults.
- How well did it protect?
- Estimated effectiveness was 81.8% against RSV hospitalization and 60.3% against any documented infection.
- Does it work in the oldest adults?
- Protection against infection was lower at 80 or older (28.6%), and that estimate was uncertain.
