People who receive mRNA COVID-19 vaccines are up to 91 percent less likely to develop the disease than those who are unvaccinated, according to a new nationwide study of eight sites, including Salt Lake City, conducted by Dr. Sarang Yoon and colleagues at the University of Utah Rocky Mountain Center for Occupational and Environmental Health (RMCOEH). For those few vaccinated people who do still get an infection, or “breakthrough” cases, the study also suggests that vaccines reduce the severity of COVID-19 symptoms and shorten its duration.

Researchers said these results are among the first to show that mRNA vaccination benefits even those individuals who experience breakthrough infections.

“One of the unique things about this study is that it measured the secondary benefits of the vaccine,” said Yoon, a study co-author and assistant professor at RMCOEH. Yoon was the principal investigator of the study called RECOVER (Research on the Epidemiology of SARS-CoV-2 in Essential Response Personnel).

Yoon said the study, published online in the New England Journal of Medicine, builds on preliminary data released by the Centers for Disease Control and Prevention (CDC) in March.

The study was designed to measure the risks and rates of infection among those on the front lines of the pandemic.

“We gave these vaccines to some of the highest risk groups in this country — doctors, nurses and first responders,” Yoon said. “These are the people who are getting exposure to the virus day in and day out, and the vaccine protected them against getting the disease. Those who unfortunately got COVID-19 despite being vaccinated were still better off than those who didn’t.”

In addition to Salt Lake City, study sites included Miami; Temple, Texas; Portland; Duluth, Minnesota; and Phoenix and Tucson, as well as other areas in Arizona.

Overall, the researchers concluded the study’s findings support the CDC’s recommendation for people to get fully vaccinated as soon as possible.