In the November 27th Mobility and Mortality Weekly Report, CDC epidemiologists confirmed the value of wearing masks based on a study conducted in Kansas from June through late August.  On July 3rd, Kansas Governor Laura Kelly (R), issued an executive order requiring face masks in public with the proviso that individual counties could opt out of the mandate.  COVID incidence rates in the twenty-four counties complying with the Gubernatorial order were compared with eighty-one non-mandated counties.  The seven-day rolling average number of new cases per 100,000 population (seven-day incidence) was compared for the periods prior to and subsequent to the mandate for the twenty-four compliant counties. There was a reduction of six cases per 100,000 population for the period August 17th-23rd compared to July 3rd-9th coinciding with the mandate.  In contrast in the eighty-one non-mandated counties, the incidence rate increased by 100 per 100,000 for the comparable period.

The authors concluded that the county-wide mask mandate contributed to a significant reduction in levels of COVID-19 transmission.  The CDC reiterates the use of masks in public, physical distancing, self-confinement when ill and avoiding congregation in large groups as practical measures to reduce COVID-19 incidence rates.

*Van Dyke, M. et al.  Trends in county-level COVID-19 incidence in counties with or without a mask mandate-Kansas, June 1st-August 23rd 2020 MMWR 69:177(2020)