Can Masks Function as a Crude Vaccine?

A new theory suggests masks lead to less severe infections that still offer immunity

Dana G Smith
Medium Coronavirus Blog
7 min readSep 11, 2020

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Credit: Emilija Manevska/Getty Images

There is mounting evidence to suggest that masks are effective at protecting people from Covid-19 both by limiting the chance someone comes into contact with the virus and by reducing the severity of the disease if they do get infected. A new opinion paper published this week in the New England Journal of Medicine takes the power of masks one step further, suggesting they could serve as a sort of crude vaccine — historically known as “variolation” — for the novel coronavirus. The idea is that masks expose people to just enough virus to cause them to develop an immune response to it but not enough to get sick.

The Medium Coronavirus Blog spoke with one of the paper’s authors, Monica Gandhi, MD, MPH, a professor of medicine at the University of California, San Francisco, about the benefits and drawbacks of the idea, which types of masks are best, and why the U.S. doesn’t have a mask mandate. The interview has been lightly edited for length and clarity.

Medium: I’m fascinated by this idea of masks as a sort of variolation, or a stop-gap for a vaccine. I’d love to hear how you came up with this theory.

Monica Gandhi: I’ve been really interested in how much asymptomatic infection there is with Covid-19. It’s very different from other respiratory viruses, or any other virus, where you can get totally sick or you can be completely fine. So I was trying to understand the risk factors for asymptomatic infection, and we started noticing that in any setting where masking was done, there’d be a lot of asymptomatic infection. In cruise ships, food processing plants — people got sick, they started masking, they didn’t get sick anymore. It really seemed to drive up the rate of asymptomatic infection from 40% as a standard to 81% on a cruise ship, 95% in jails, and 95% in food processing plants when they started giving masks routinely.

In our article in the Journal of General Internal Medicine that came out three or four weeks ago, we tried to put together all the evidence for why that would be. And, essentially, masks reduce your viral inoculum [the amount of virus a person is exposed to]. It’s very well known in science that the…

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Dana G Smith
Medium Coronavirus Blog

Health and science writer • PhD in 🧠 • Words in Scientific American, STAT, The Atlantic, The Guardian • Award-winning Covid-19 coverage for Elemental