Not only are people vaccinated against COVID-19 less likely to die of that disease, they're also less likely to die from any cause, a new study shows.

Researchers compared 6.4 million people who were fully vaccinated against COVID-19 to 4.6 million people who received flu shots in recent years but weren't vaccinated against COVID-19, CNN reported.

Compared to unvaccinated people, those who had two doses of the Pfizer vaccine were 34% as likely to die of non-COVID-19 causes over the following three months, those who had two doses of Moderna vaccine were 31% as likely, and those who got the single-dose Johnson & Johnson's Janssen vaccine were 54% as likely to die, according to the findings published Oct. 22 in the U.S. Centers for Disease Control and Prevention's Morbidity and Mortality Weekly Report.

The lower death risk "after COVID-19 vaccination suggests substantial healthy vaccine effects [i.e., vaccinated persons tend to be healthier than unvaccinated persons], which will be explored in future analyses," study leader Stanley Xu, a researcher at the Kaiser Permanente Southern California Department of Research and Evaluation, and colleagues wrote.

The researchers launched the study to assess the safety of the three COVID-19 vaccines authorized for use in the United States.

"COVID-19 vaccines authorized in the United States have shown again and again to be safe. This study also confirms their safety," Xu told CNN.

"This finding reinforces the safety profile of currently approved COVID-19 vaccines in the United States. All persons aged 12 years and older should receive a COVID-19 vaccine," the researchers concluded.