Thread by @TorreyJaeckle

I have been very curious about the effects of mask mandates during the Omicron surge. We had 7 states with full indoor mask mandates (CA, HI, IL, NM, NY, OR, WA), one with an unvaccinated only mandate (CT), plus the District of Columbia.

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Using data obtained from the CDC (covid.cdc.gov/covid-data-tra…) I plotted out the 7-day case rate per 100,000 in various ways, comparing the mask mandate states (Red) to the non-mandate states (Blue).

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First I looked at the average for each group, and there is largely no difference in case rates between the two during Omicron.

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Then I looked at the median for each group to factor out any outliers that might be affecting the data. Still no difference.

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Then under the theory that more condensed living in more populous states could impact the results (greater likelihood of higher case rates), I compared the group of all mask mandate states to all remaining Top 10 most populous states (7 total). Again I found no difference.

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Finally, because I noticed that that non-mandate states had higher infection rates during the Delta surge, I wanted a way to factor out the potential effects that prior infection immunity might have had on Omicron infection rates.

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I isolated 15 states that had very close pre-Omicron case rate histories to the group of mask-mandate states. But again, there was no difference in case rates during the Omicron surge.

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In the end, I have been unable to find any meaningful difference in terms of Covid spread between mask-mandate and non-mandate states. If masks played a role in limiting spread, it is not readily apparent in the overall data.

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Update: I now have learned that Rhode Island also had a mandate in effect. However, adding RI to the mix actually makes things look worse for the mask mandate states.