Recently two physicians at the University of California at San Francisco published a commentary in the New England Journal of Medicine (NEJM) where they float a provocative — and unproven — idea: that masks expose the wearer to just enough of the virus to spark a protective immune response.
Suggesting to revive the 18th-century practice of variolation using face covers to prevent severe COVID-19 and confer immunity.
This has created a buzz on the Internet with headlines such as “Coronavirus: Another reason for that mask: You’ll get less sick.”
The paper, written by Monica Gandhi, MD, MPH, and George Rutherford, MD, suggested that face coverings, in the absence of a vaccine, could reduce the inhaled dose of coronavirus by filtering some virus-containing droplets, leading to asymptomatic or mild disease and stimulating T- and B-cell immunity.
Worried scientists warned against the practice in two letters to the editor in the same journal on Oct 23, that the published article, its positioning in a top medical journal, and the resulting media coverage would embolden people to abandon physical distancing and other public health measures in favor of only wearing face coverings.
Printing a hypothesis—without telling the experiments that would need to prove or disprove it—in a prominent journal like NEJM sends the message that the concept has been borne out by evidence, said Angela Rasmussen, Ph.D., an associate research scientist at the Center for Infection and Immunity at Columbia University and co-author of the first letter, adding that the paper would have been acceptable had it been framed as only a hypothesis.
“I think that could encourage irresponsible behavior,” she said.
Rasmussen added, “People should be wearing masks, but they should also be social distancing; masks are not the only nonpharmaceutical intervention.”
Chad Roy, Ph.D., MSPH, of Tulane University School of Medicine, co-author of the second letter, along with Lisa Brosseau ScD, CIH, and Michael Osterholm, Ph.D., MPH, both of the Center for Infectious Disease Research and Policy, publisher of CIDRAP News, called the proposal of variolation “borderline heresy” in terms of modern vaccine design and all of its complexities.
“Variolation was used historically as an incredibly crude way of vaccinating individuals, but it was a completely uncontrolled mechanism by which to achieve vaccination,” Roy said. “Variolation should be considered an antiquity and not anything that anyone would try to use in modern medicine.”
Also problematic is that no one knows what constitutes an infectious dose of the coronavirus, which likely varies from person to person and doesn’t appear to follow a classic dose-response relationship, Rasmussen said. And although it seems counterintuitive, high doses of coronavirus can be less virulent than low ones, Rasmussen said.
That’s because viruses mutate, some to the point that they can no longer cause infection, and may thereby alter a host’s immune response to the virus.
“They think the more virus you have the sicker you’re going to get, but that’s not necessarily true,” she said, adding that it probably depends more on the proportion of noninfectious-to-infectious virus.
“There’s not always a linear relationship between dose and disease severity and outcome.”
Roy pointed out the complexity of trying to define infectious dose in a virus that doesn’t necessarily cause symptoms, even in people with high viral loads. “Most particles are probably empty and just made up of mucous and water with no virions, or else everyone would be infected,” he said.
An additional problematic aspect with the perspective piece is that it doesn’t define what the authors consider a face covering, which ranges from single-layer homemade cloth masks to dependable N95 respirators, according to Rasmussen.
“Certainly, masks could probably block larger droplets, and that kind of gets into the area of the whole droplet-versus-aerosols debate,” she said.
“We just don’t have much evidence that masks protect the person wearing them, unless they are N95s certified by [the National Institute for Occupational Safety and Health].”