But the vast majority of the masks used by the public do NOT retard the spread of the virus so a general assumption of efficacy is untrue.
I've posted this a couple times the past few days, but it bears repeating. If you analyze the results in mask mandate states (39) versus the no-mask mandate states (11), you find the results are the same. Notice that the no-mask mandate states did better than the mask mandate states in the Fall-Winter 2021 surge.