"The Case for Universal Cloth Mask Adoption & Policies to Increase the Supply of Medical Masks for Health Workers" by me @judy_chevalier @NAChristakis @thehowie E Kaplan, A Ko (Chair of Epidemiology @yale) S Vermund (Dean of School of Public Health @yale) dropbox.com/s/6ua7j979dbqb…
We have two principal recommendations: 1) everyone should immediately begin wearing cloth masks in public, 2) The govt. should immediately use all available means to increase the supply of medical masks, especially by heavily rewarding producers.
The basis for our recommendation is simple: anything that combats the spread of the virus is absurdly valuable due to the resulting reduction in mortality risk (not to mention accelerating resumption of normal economic activity).
We have very good evidence that universal adoption of cloth masks will combat the spread of the virus. Specifically, we know that 1) asymptomatic people spread the virus, 2) mask wearing by infected people prevents them from transmitting the virus (the report provides citations).
How large are the benefits? Even if masks reduce transmission probabilities by only 10% (and as you'll see, that is likely very conservative), the value of *each cloth mask* is between $3,000 and $6,000. Our best estimate is that their protective value is closer to 40-50%.
These estimates are of course sensitive to the assumptions made in the underlying epidemiological models. But even if those models overstate mortality risk by a factor of TEN, each cloth mask *conservatively* generates $300 in value!
So we must urgently promote universal cloth mask adoption. Why cloth masks? Because there is one policy with *even larger* benefits at the current moment than the average person wearing masks.
That policy is getting more medical masks to healthcare workers. The same economic argument that says that masks for the average person are worth thousands of dollars suggests that each N95 respirator for a healthcare worker could be worth *millions* of dollars (report says why).
This is not just us making up numbers to say something is important – in a pandemic situation, it is possible that each medical mask for a healthcare worker saves a life in expectation by containing the spread of the virus. So donate your medical masks today!
If recommending that everyone wear masks resulted in medical personnel being unable to get medical masks, even in the short term, this would be a serious problem.
This is why we recommend universal adoption of *cloth masks*, at least until there is no (domestic or global) shortage of medical masks for healthcare workers. Homemade cloth masks do not interfere with the production of medical masks.
We should encourage people with cloth masks to donate medical masks, and hopefully, universal cloth mask adoption will make health workers *safer* by slowing the spread of the virus. But additional policies are needed.
Our main policy recommendations are: first, the purchase of medical masks should receive very large subsidies, several times larger than their usual prices.
Priority should be given to orders from medical personnel, using fines or other penalties for any manufacturers who fail to prioritize these orders. The DPA should also be invoked, but is not a substitute for heavily rewarding private manufacturers who produce masks.
Such rewards are necessary to incentivize private manufactures to expand capacity now. This expanded capacity will be crucial as the epidemic spreads globally, and will also send the right signals to manufacturers to stockpile for future pandemics.
Additionally, technologies and strategies for mask sterilization and reuse should be deployed as a stopgap until N95 respirators are available for all health workers.
Our second major policy recommendation is: everyone else should immediately produce and wear cloth masks when in public.
Where do we get that these would reduce transmission of the virus by 40-50%? One source of evidence is direct medical studies investigating the ability of droplets to penetrate such masks.
We also consider the cross-country evidence -- we replace and extend the twitter-famous graph countries with and w/o masks. Thanks to the internet for helping us collect data (which we subsequently checked: ).
We show a similar result holds with a wider range of countries, that it holds using death as an outcome instead of positive tests, and that it holds when we control for a few observed policy variables.
Attached is our version of the graph, with blue countries having norms of mask-wearing for sick people, green countries having no such norms but adopting mask regulations in response to the spread of the virus, and orange countries doing neither. 
Our main result is that growth of the virus is slower in blue countries. Of course, many policies are not controlled for, such as better tracking policies or norms that avoid handshakes, among others. We will post all data and analysis later today in Github (and I'll tweet it).
The report points out the many needed caveats. This analysis is not meant to be definitive. But it is also mistaken to dismiss this evidence out of hand. The cross-country evidence should move our priors in the direction of masks working, especially given the clear mechanism.
To reiterate, the case for universal cloth mask adoption is extremely strong. The best evidence indicates that the benefits of universal adoption of cloth masks are likely thousands of dollars *per mask* because masks prevent transmission of the virus from asymptomatic people.
The biggest concern with this policy is that broader mask adoption will jeopardize the availability of masks for healthcare workers. This is a serious concern, so concurrent policies are necessary to expand the supply of medical masks.
Promoting homemade cloth mask-wearing mitigates the risk to healthcare workers while policies designed to combat the shortage of medical masks kick in. Neither policy can wait. Both are urgently needed and should be pursued immediately.
