On Dec.10 you quoted the chair of the Greenfield Board of Health as saying that “one of the things that we know is effective, is wearing masks.” That isn’t correct.
When I challenged the Shelburne Board of Health in October over a similar claim, they simply referred me to the CDC and Massachusetts Department of Public Health websites, but there’s no such data there. (To their credit, the Shelburne board has subsequently rescinded its mandate.)
For those who don’t have time to read the relevant published research, I would recommend a recent survey compiled by the Cato Institute, which is available at https://bit.ly/31W2gm7.
It reaches the following conclusions:
Mechanistic studies show that under (mostly unrealistic) experimental conditions, masks reduce the ejection of droplets, but there has been no demonstration of a positive effect on spread of respiratory illness. (COVID-19 is mostly spread by aerosols.)
There have been two large-scale randomized controlled trials of the effect of mask wearing on the spread of COVID-19 in a community setting, one of which failed to find any statistically significant benefit to wearing masks, and the other of which (the Bangladesh study) purported to find a statistically significant benefit to wearing surgical masks (but none for cloth masks). However, in the Bangladesh study, the claimed statistical significance was marginal, and the benefit was very small.
For anyone interested in a critical review of the Bangladesh study, I would recommend the analysis by Berkeley professor Ben Recht here: https://bit.ly/3yxBOuD. Recht obtained the underlying data from the study authors and concluded that even their claim of a small mask benefit with marginal statistical significance is invalid. A recent study by Guerra and Guerra found no positive relationship between mask mandates or mask use and case growth on a U.S. county-by-county basis: https://bit.ly/3GPzbYg.
John R. Harrington
Shelburne