This is another of those studies that clearly was done to try to justify the use of a particular treatment, in this case a vaccine, but the study itself is quite weak. Respiratory syncytial virus is usually thought of as a problem in children but it can affect adults as well, and particularly older adults. Vaccines have arisen in the last couple of years and of course the manufacturers are trying to expand their use to make more money. This study looked at effectiveness in a nursing home setting. These institutions are likely breeding grounds for all kinds of infections so there is rationale for use there. About 600,000 fee-for-service Medicare beneficiaries who were in a nursing home for at least one day were studied during the period September 2023 to March 2024. (JAMA Article)
The first thing to note is that including people who were in a nursing home for very short days is misleading about effectiveness in nursing homes. The study should have been limited to longer stays, at least three months, but 53% of subjects were characterized as short stay–less than 100 days. The study relied on claims data and grouped the subjects by RSV-associated events. How they determined an event was “associated” with RSV is beyond me and not described as other than an assumption that if there was an RSV diagnosis, all health care was due to that infection, so apparently it is like CV-19 deaths, if you ever had CV-19 and you die at some point, it must have been because of CV-19. Supposedly vaccine effectiveness against hospitalization was 73%, meaning a vaxed person was 73% less likely to be hospitalized; against death was 56% and against a “severe” outcome was 59%. All these had wide confidence intervals, undermining any definitive result.
This is a very sloppy study, and one of its flaws is complete failure to identify pre-existing RSV immune response from prior infections. As we learned with CV-19, this is an extremely relevant confounder. We also see the usual effect with respiratory virus vaccines–effectiveness weakens quickly after vaccination. And we get no information about adverse events. The best that can be said is that there is very weak evidence that the vaccines will protect against severe RSV outcomes in nursing home residents, especially people who were real residents with long stays.
