NPR looked at deaths per 100,000 people in roughly 3,000 counties across the U.S. from May 2021, the point at which vaccinations widely became available. People living in counties that went 60% or higher for Trump in November 2020 had 2.7 times the death rates of those that went for Biden. Counties with an even higher share of the vote for Trump saw higher COVID-19 mortality rates.

The trend was robust, even when controlling for age, which is the primary demographic risk of COVID-19 mortality. The data also reveal a major contributing factor to the death rate difference: The higher the vote share for Trump, the lower the vaccination rate…

“An unvaccinated person is three times as likely to lean Republican as they are to lean Democrat,” says Liz Hamel, vice president of public opinion and survey research at the Kaiser Family Foundation, a nonpartisan health policy think tank that tracks attitudes toward vaccination. Political affiliation is now the strongest indicator of whether someone is vaccinated, she says: “If I wanted to guess if somebody was vaccinated or not and I could only know one thing about them, I would probably ask what their party affiliation is.”