For all the talk about how much masks help, I haven't seen great studies that aren't in vitro, not specifically in health care settings, and not specifically around someone known to have it. I found this which is at least a natural experiment:
> Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1,1.4, 1.7, and 2.0 percentage points in 1–5, 6–10, 11–15, 16–20, and 21 or more days after state face mask orders were signed, respectively.
I'm trying to sort of if those percentages are absolute or relative. I think they're absolute because some of the graphs are labeled "percentage point change," but using absolute percentage point changes for an analysis like this is seriously flawed because a 2% reduction could range anywhere from a miracle to statistically significant, but negligible.
It's also not clear if people feel safer wearing face masks, so they engage in riskier activities.
My guess is they're not as effective as claimed because while the Bay Area has pretty high compliance, if masks were systemically very effective, we'd see case rates drop a lot faster, not still be above mid-June numbers. That said, whatever the Bay Area is doing right now is working.
https://www.healthaffairs.org/doi/pdf/10.1377/hlthaff.2020.0...
> Mandating face mask use in public is associated with a decline in the daily COVID-19 growth rate by 0.9, 1.1,1.4, 1.7, and 2.0 percentage points in 1–5, 6–10, 11–15, 16–20, and 21 or more days after state face mask orders were signed, respectively.
I'm trying to sort of if those percentages are absolute or relative. I think they're absolute because some of the graphs are labeled "percentage point change," but using absolute percentage point changes for an analysis like this is seriously flawed because a 2% reduction could range anywhere from a miracle to statistically significant, but negligible.
It's also not clear if people feel safer wearing face masks, so they engage in riskier activities.
My guess is they're not as effective as claimed because while the Bay Area has pretty high compliance, if masks were systemically very effective, we'd see case rates drop a lot faster, not still be above mid-June numbers. That said, whatever the Bay Area is doing right now is working.