The week before Gov. Roy Cooper announced his statewide mask mandate, DHHS Secretary Mandy Cohen went in front of the NC House Health Committee to make the case for masking the public. This week, JLF’s Jon Sanders took the liberty of examining the evidence Cohen provided to support a mask mandate. Sanders writes:

Cohen’s presentation included a slide on “Slowing the Spread of the Virus” that included this: “Research on Effectiveness of Face Coverings.” Basically, this research amounts to the administration’s case for requiring face masks statewide. Here is Cohen’s summary of their findings:

  • As many as 230,000 to 450,000 COVID-19 cases may have been averted by May 22 due to face-covering mandates in 15 states and DC.
  • Face covering reduced the number of infections by over 78,000 in Italy (from April 6 to May 9) and by over 66,000 in NYC (from April 17 to May 9).
  • In Germany, the daily growth rate of COVID-19 cases fell by ~40% due to mandatory mask-wearing.


Lyu and Wehby. Community Use Of Face Masks And COVID-19: Evidence From A Natural Experiment Of State Mandates In The US. Health Affairs. June 16, 2020.

Zhang et al. Identifying airborne transmission as the dominant route for the spread of COVID-19. Proceedings of the National Academy of Science. June 11, 2020.

Mitze et al. Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach. Institute of Labor Economics. June 2020.

At first glance, these studies look highly promising, but when our Jon Sanders dug into the matter, the relevance of these studies to North Carolina was found to be highly questionable. For example, Zhang et al piece, Sanders explains:

North Carolina never approached the level of outbreak experienced by Italy and NYC. Those places experienced the feared epidemic “spike” curve, the one that NC and other jurisdictions sought to avoid by adopting policies to “flatten the curve,” i.e., spread out infections so as not to overwhelm hospitals. NC’s curve was flattened, with hospitalizations higher now but still not anywhere near the projected, flattened-curve peak.

What’s more, Sanders writes:

Bear in mind that the epidemic spike not only features a sharp increase in infections before reaching peak infections, but it also features a sharp dropoff in infections afterward. If a policy intervention was made after the peak of infections and during the steep dropoff, it could be credited wrongly for this natural decrease.

That is important because Italy and NYC began mandating masks AFTER the peak began to naturally decline.

What does this mean for this study’s applicability to North Carolina? Sanders writes:


Italy and NYC’s epidemic spike curves are completely different from NC’s flattened curve. Also, Italy and NYC’s impositions of their mask mandates well after their peak of daily new cases makes it difficult to ascertain how much actual effect their mask mandates had on cases. Expecting a linear progression of cases post-peak also seems inflationary to the number of cases (under a no-mask assumption) over time.


The applicability of this study to North Carolina is highly questionable.

Read Sander’s full examination of each study in his research brief here. Read more research briefs like this one in our COVID-19 series here.