RSV vaccine succeeds in phase 3 trial of adults ages 60 and older.

An important new study came out yesterday in the New England Journal of Medicine which found that a candidate vaccine against RSV was highly effective in preventing lower respiratory tract (read: lung) disease. The study also found the vaccine prevented severe disease.

The study has many of the features you want to see from a well-conducted study: the vaccine was compared to placebo and the study was blinded, meaning that participants and the scientists carrying out the analysis were not aware of who got what. The study had 25,000 participants and was carried out across 17 nations.

The vaccine was found to be over 80% effective against lower respiratory tract disease (the main outcome the study was designed to measure) and 94% effective against severe disease. This is great news.

The study took place from May 2021-January 2022, meaning the Covid-19 mitigation was still in place. As a result, the rates of RSV were lower than we might normally expect—that is, rates were low in the placebo group and vanishingly low in the vaccinated group.

I was curious what these data could mean on a population level during a “normal year.” Assuming that the vaccine is also 94% effective in preventing RSV-related hospitalizations, I applied CDC surveillance data to the study’s findings to get some idea of the impact this vaccine could have for seniors.

In the US, there are around 76.5 million people ages 60 and over. In the last pre-Covid season, approximately 45.1 people out of every 100,000 in the entire US population ages 60 and up had an RSV-related hospitalization. That means around 34,500 people in this age group got hospitalized in one season (2019-2020) with RSV. If the vaccine prevented 94% of these, that number would fall to just above 2,000. I think that’s a relevant decrease—and the real improvement may be even greater, as we get better at tracking RSV in general.

Another study, also out in the New England Journal also found encouraging data for a different vaccine platform. A commentary describing the technical challenges that have finally been surmounted in developing vaccines for RSV was also published alongside these two research articles.

If we can decimate flu, Covid, and RSV-related hospitalizations in the future, both patients and the healthcare system may finally get a well-deserved break.

These new data are important pieces of that puzzle, and as the kids say, “We love to see it!”