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A New Theory Asks: Could a Mask Be a Crude ‘Vaccine’?

Scientists float a provocative — and unproven — idea: that masks expose the wearer to just enough of the virus to spark a protective immune response.

As the world awaits the arrival of a safe and effective coronavirus vaccine, a team of researchers has come forward with a provocative new theory: that masks might help to crudely immunize some people against the virus.

The unproven idea, described in a commentary published Tuesday in the New England Journal of Medicine, is inspired by the age-old concept of variolation, the deliberate exposure to a pathogen to generate a protective immune response. First tried against smallpox, the risky practice eventually fell out of favor, but paved the way for the rise of modern vaccines.

Masked exposures are no substitute for a bona fide vaccine. But data from animals infected with the coronavirus, as well as insights gleaned from other diseases, suggest that masks, by cutting down on the number of viruses that encounter a person’s airway, might reduce the wearer’s chances of getting sick. And if a small number of pathogens still slip through, the researchers argue, these might prompt the body to produce immune cells that can remember the virus and stick around to fight it off again.

“You can have this virus but be asymptomatic,” said Dr. Monica Gandhi, an infectious disease physician at the University of California, San Francisco, and one of the commentary’s authors. “So if you can drive up rates of asymptomatic infection with masks, maybe that becomes a way to variolate the population.”

That does not mean people should don a mask to intentionally inoculate themselves with the virus. “This is not the recommendation at all,” Dr. Gandhi said. “Neither are pox parties,” she added, referring to social gatherings that mingle the healthy and the sick.

Experiments in hamsters have hinted at a connection between dose and disease. Earlier this year, a team of researchers in China found that hamsters housed behind a barrier made of surgical masks were less likely to get infected by the coronavirus. And those who did contract the virus became less sick than other animals without masks to protect them.

A few observations in humans seem to support this trend as well. In crowded settings where masks are in widespread use, infection rates seem to plummet. And although face coverings cannot block all inbound virus particles for all people, they do seem to be linked to less illness. Researchers have uncovered largely silent, symptomless outbreaks in venues from cruise ships to food processing plants, all full of mostly masked people.

Data linking dose to symptoms have been gathered for other microbes that attack the human airway, including influenza viruses and the bacteria that cause tuberculosis.