Study indicates COVID-19 boosters among vaccinated individuals significantly reduce hospitalization rates

A Providence study released online today in the Journal of the American Medical Association sheds new light on the added benefit of a booster dose of a COVID-19 mRNA vaccine among previously vaccinated individuals.

Researchers found that boosters add about 70% extra protection, which lasts for 4–5 months, and concluded that booster vaccination is associated with significantly decreased odds of hospitalization for COVID-19 among fully vaccinated individuals. Odds of decreased hospitalization varied based on time since booster administration.

While previous studies have established the association between boosters and decreased risk of developing severe COVID-19 when compared with unvaccinated individuals, this study is unique in its focus on individuals who are already fully vaccinated with the primary series of an mRNA vaccine. It adds to the growing body of research around the effect of booster doses in various populations.

This research shows us that even if you're fully vaccinated, there's a real value to getting a booster," said Ari Robicsek, M.D., Providence's chief medical analytics officer and senior author of the study. "Compared to people who only had their initial vaccinations, people with boosters were a lot less likely to have severe COVID for 4–5 months after the booster shot."

Providence, a not-for-profit health system serving the Western U.S., conducted the research at sites across six western states. It matched 3,052 cases hospitalized for COVID-19 within a Providence facility 4:1 with 12,248 controls admitted to a Providence facility non-electively for reasons other COVID-19. Cases were hospitalized between October 1, 2021, and July 26, 2022, and controls were admitted to a facility within three days in the same geographic location as their case and received a second vaccine within seven days of their case.