Mask Mandates Associated with 60% Reduction in COVID-19

Kansas counties that adopted mask mandates during the COVID-19 pandemic saw fewer cases, hospitalizations and deaths from the disease than those without mandates, a new study found.

The research letter, published in JAMA Network Open, evaluated 15 counties that adopted the Kansas executive order calling for mask mandates and 68 counties that did not between July and October 2020.

“Mask mandates were effective at slowing the spread of COVID-19 cases, hospitalizations and deaths in counties that adopted them,” lead author Donna Ginther, PhD, director of the Institute for Policy & Social Research at the University of Kansas told Contagion. “Our estimates show that those counties had 35,000 fewer cases, 1,500 fewer hospitalizations and over 500 fewer deaths.”

The study, co-written by Carlos Zambrana, an associate researcher at the Institute for Policy & Social Research, included data from the New York Times and the Kansas Department of Health and Environment. The investigators used linear regression difference-in-difference models to allow for changes in mask wearing behavior after mandates were adopted.

At the time the mask mandate was adopted, rates of COVID-19 were 3 times higher in counties that adopted the masking requirement, with 15 cases per 100,000 population compared with 5.

By Oct. 26, case rates in counties without mask mandates shot past those with mask mandates. At that time, those counties without mask mandates saw 2.1 times more cases at 44 cases per 100,000 population compared with 21 cases per 100,000 population in those with mask mandates. By mid-October, hospitalization rates were 1.4 times greater in counties without mask mandates (2.6 hospitalizations per 100,000 population compared with 1.8).

Through Dec. 4, cases and hospitalizations per day were reduced by 60% and deaths dropped by 65% in counties that adopted mask mandates, the study showed. Cases per day were 20.33 lower in counties with mask mandates (95% CI, −26.54 to −14.12) compared with a mean of 34.18 (95% CI, 33.31 to 35.06). Hospitalizations per day in those counties were 0.81 lower (95% CI, −1.21 to −0.40) compared with a mean of 1.35 (95% CI, 1.30 to 1.39). Deaths were lower by 0.29 (95% CI, −0.51 to −0.08) compared with a mean of 0.45 (95% CI, 0.42 to 0.48).

“We were surprised by how consistent the reductions were across the board (60% compared to non-mask counties for cases and hospitalizations and 65% for deaths),” Ginther said. “Mask mandates and mask-wearing are an effective approach to slowing the spread of COVID-19.”

Limitations of the study include that it did not control for daily testing rates, which were not available. It also doesn’t equate mask mandates with compliance.

“We are in the process of examining whether the mask mandates had any effect (positive or negative) on economic activity,” Ginther said.

In May, the US Centers for Disease Control and Prevention issued new guidance for mask wearing, announcing that people who are fully vaccinated against COVID-19 no longer needed to wear masks. The announcement was met with surprise and concern among some in the healthcare community.

The Kansas study is consistent with previous research, including a study in Delaware, that found mask mandates, along with stay-at-home orders and contact tracing were associated with significant drops in COVID-19 incidence and mortality.