New data released Nov. 10 from Vanderbilt University Medical Center shows counties in Tennessee with mask mandates have lower coronavirus-related death rates than counties without mask mandates.

A recent study from VUMC led by John Graves, associate professor of health policy and director of the Vanderbilt Center for Health Economic Modeling, found that counties with mask mandates saw death rates decline in later months, while counties without mandates saw death rates rise.

“This analysis shows that strategies, including but not limited to masking while in contact with others, can have real impact on people’s lives,” Graves said. “Mask mandates are associated with greater mask wearing and other behaviors like limiting close contacts with others, and the combined impact is clear and substantial.”

In Williamson County, officials instituted a mask mandate in the summer but allowed it to expire Aug. 29 as cases began to decline.

However, the county instituted a new mandate in October after the area began to see large increases in new cases. The new mandate is scheduled to last through at least Dec. 29.

As of early November, about two thirds of the state is under a mask mandate. Tennessee Gov. Bill Lee has not instituted a statewide mandate but has allowed county mayors the power to institute a mandate at the local level.

The study uses data from up to Oct. 1, before the recent surge in new cases, according to VUMC. Another study from late October also found that areas without mask requirements had higher rates of coronavirus-related hospitalizations.

Researchers said it can take some time for death rates to decline after a mask mandate is instituted, as deaths due to coronavirus typically follow other data markers.

“Deaths are a lagging indicator, following increases in cases and then hospitalizations, so we expect any intervention such as a mask requirement to take some time to demonstrate effectiveness," said Melissa McPheeters, research professor of Health Policy and Biomedical Informatics in a VUMC release. "Rising rates of COVID-19 are a big ship to turn, and it is important to act early enough to be effective.”