A new theory published in an opinion paper in the New England Journal of Medicine this week suggests that masks lead to less severe infections that still offer immunity. Elemental senior writer Dana Smith spoke to paper author Monica Gandhi, MD, MPH, a professor of medicine at the University of California, San Francisco, about the benefits and drawbacks of using masks as a poor man’s vaccine, which types of masks are best, and why the U.S. doesn’t have a mask mandate. Here’s an excerpt of the interview:
Elemental: I’m fascinated by this idea of masks as a sort of variolation, or a stopgap 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 lower viral inoculum you get, the less sick you get. So putting it all together, it seems like masks increase rates of asymptomatic infection by decreasing viral inoculum.
Then, over the last month, we’ve been getting these amazing studies about asymptomatic infection leading to really strong T cell immunity. This isn’t shocking because it’s actually probably the process by which you get asymptomatic infections — the lower viral inoculum allows you to have a really strong and organized adaptive immune response. And we’ve been seeing cases go up in places that have opened up, like San Francisco, but the case fatality rate has been so low in cities that mask compliantly. So are we actually getting immunity by getting cases with our masks but not getting fatalities?
Read the full interview below.