Tennessee counties that aren’t mandating masks are reporting death rates at least twice as high as those requiring face coverings. That’s according to new research published Tuesday by Vanderbilt University.

There are currently more than four deaths per 100,000 people each week in areas with no mandate, compared to a death rate of two deaths per week in areas that adopted a requirement over the summer. In the “early adopter” counties that required masks before the worst surge in July and August, the death rate is closer to one per week for every 100,000 people.

That lines up with WPLN News’ analysis of death rates by county over the course of the pandemic. Nashville, which has been under a mask mandate since late June, has reported 53 deaths per 100,000 people since March. Clay County, on the other hand, has no mask mandate. It’s now reporting 223 deaths per 100,000 people since the pandemic started, the worst death rate in the state.

Vanderbilt’s data shows less than two-thirds of Tennesseans live where masks are currently required. Many counties previously had mandates but let them expire, and 8% of residents live where local governments have never required masks in the pandemic.

Researchers say the good news is that more than 80% of Tennesseans report they are wearing masks as of this month, according to data from Carnegie Mellon University. That’s despite the fact that Gov. Bill Lee has continued to reject the idea of a statewide mandate.