Study Finds COVID Vaccine Particularly Benefits Patients Who are Obese, Older

In a recent study, researchers from the University of Wisconsin found that having a COVID-19 vaccination reduces the likelihood of dying from COVID and the size of this effect differs across different patient groups. In particular, the benefits of vaccination are especially great for some of those who otherwise would have had the greatest risk of SARS-CoV-2 mortality. Results are now published in the Journal of General Internal Medicine.

In an assessment of 86,732 patients hospitalized with COVID-19 sometime during January 1, 2021 to January 31, 2022, the researchers found that mortality amongst the unvaccinated was at 8.3% and only 5.1% amongst the vaccinated. However, when immune-compromised patients were removed from the analysis sample (who were unlikely to develop an immune response related to vaccination), the results are even clearer: the mortality rate was 7.9% for unvaccinated patients, and only 3.5% for the vaccinated.

“Vaccination more than halved the likelihood of mortality amongst patients who were not immune compromised,” said Dr. Timothy Baker, UW-CTRI co-founder, Associate Director, and Director of Research. “We also saw somewhat greater reductions in mortality risk for some particular populations. For instance, the obese and severely obese and older patients appeared to benefit especially from vaccination. These patient groups had particularly high mortality rates if they were not vaccinated.

“Surprisingly, however, there was not a strong association between number of vaccine doses and mortality amongst those who were vaccinated.”

The researchers also noted that mortality rates shifted over the course of the year-long study and did so especially for vaccinated patients whose mortality increased to nearly 6.5% for vaccinated patients in the last 6 months of the study.

Dr. Baker speculates that this significant increase may be the result of changing COVID variants over the course of the pandemic.

“Or,” he said, “it may reflect other, unknown factors.”

One thing remains clear: vaccination reduces the risk of mortality across the board. Vaccinated patients were substantially less likely to die than unvaccinated patients.


Contact: Matthew Bettencourt, University of Wisconsin, or 651-269-9892