Interesting but hardly conclusive.
It could have been a situation where the hard hit places no longer could be hit as hard.
We saw cities get slammed and then later the center of the country.
for instance...
"Second, this analysis did not account for mask ordinances in six cities in non–mask-mandated counties. However, in sensitivity analyses recategorizing nonmandated counties that included cities mandating masks as mandated counties, results were consistent with those in primary analyses, although they were attenuated. In those analyses, after the governor’s executive order, COVID-19 incidence among mandated counties stabilized rather than decreased, and incidence continued to increase among nonmandated counties."
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