Robert Gordon, Director, Michigan Department of Health and Human Services, says that wearing masks can reduce the chance of transmitting COVID by about 70%. He’s got 4 links:
Scientific research - the Conclusions were “We detected an immediate and significant reversal in SARS-CoV-2 epidemic suppression after relaxation of social distancing measures across the U.S. Premature relaxation of social distancing measures undermined the country’s ability to control the disease burden associated with COVID-19.” Social distancing, nothing about masks here.
Linked mandates - The Introduction states “Our estimates imply that nationally implementing mandatory face masks for employees in public businesses on March 14th would have reduced the growth rate of cases and that of deaths by approximately 10 percentage points in late April. As shown in Figure 1, this leads to reductions of 21% and 34% in cumulative reported cases and deaths, respectively, by the end of May with 90 percent confidence intervals of [9, 32]% and [19, 47]%, which
roughly implies that 34 thousand lives could have been saved.”
This does not support Gordon’s 70% figure. Nor does it inform us on the effect as of now, as some of the lives saved by the end of May might have been lost after that. However, a reduction in deaths by 34% is a significant finding, if true.
The paper continues with “Whether wearing masks in public place should be mandatory or not has been one of the
most contested policy issues with health authorities of different countries providing contradictory recommendations. Reviewing evidence, Greenhalgh et al. (2020) recognize that there is no randomized controlled trial evidence for the effectiveness of face masks, but they state “indirect evidence exists to support the argument for the public wearing masks in the
Covid-19 pandemic.”
Reductions - The link says 25 to 40%, not 70%
COVID’s spread - Abstract has declines in the daily COVID growth rate ranging from 0.9 to 2.0% for periods ranging from 1 to 21 days. Nothing about a 70% reduction.
This was the first time I’ve seen anyone quote a figure for the reduction in transmission. Interestingly, the CDC website had nothing quantitative when I looked on September 30th.
Here’s a link to Gordon’s statement:
https://www.michigan.gov/mdhhs/0,5885,7-339-73970_71692-541432—,00.html
Thanks. Those links are helpful, but if that’s all he’s got, the “science” is far from clear. The most promising is the “linked mandates” article. The summary hints at some useful conclusions, but again, we need to look at the data, the methodology, the basis of estimates to determine if they were justified. Furthermore, the study is retrospective (actions taken in April may be useless today); it refers to “employees”, not to the general public; it doesn’t compare “mandatory” to “voluntary”; it uses the weasel word “imply”. Etc, etc.
If I were a public decision maker, this article would incline me to encourage voluntary masking of employees at public businesses to see if it helps. That is, assuming, after reading the research carefully, I don’t conclude it’s full of crap. If the research were particularly compelling, I might even encourage mandatory masking of employees of public businesses, for a time, and, after a time, see if it made any difference. And I’d carefully define what an effective mask was. I wouldn’t conclude “everyone must wear masks at all times under penalty of law, civil liberties be damned; the science is clear”.