Association of State-Issued Mask Mandates with COVID-19 Case and Death Counts

"Abstract

We have interpreted and extended an analysis published on the US CDC website 5 March 2021, which calculated the benefits of imposed mask mandates. Historical studies of masking in the general population have produced contradictory results with respect to their effectiveness in stemming spread of respiratory viral infections. The CDC study is based on a comparison of Daily Growth Rate (DGR) in number of COVID cases (or deaths) before and after imposition of mask mandates. We show that the downward trend in DGR began before masking and continued after masking. We add controls to the CDC methodology by comparing states that imposed mask mandates to states that did not. We report evidence of short-term benefit for the first 30 days that is lost when DGR increased in the fall more in masked states than unmasked...

Discussion

... In our examination by county of daily cumulative cases of Covid-19, using data extracted from the CDC’s (publicly-available) National Environmental Public Health database, we were able to identify two pairs of states where reasonable comparisons between a mask vs no mask mandate could be made. In each pair, the state with no mask mandates was more densely populated, yet suffered essentially the same burden of disease as their masked counterpart.

Our investigation parallels a recent study comparing European countries with severe lockdown and masking restrictions to other countries with looser restrictions. Bjørnskov found no evidence that the restrictions affected COVID case rates, consistent with our US comparisons.

We find that the benefits that CDC attributes to lockdowns and masking can largely be explained by saturation effects and seasonality."