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Paris (AFP)
Could the mask, already seen by many scientists as the most effective shield against Covid-19, have another benefit? Some researchers now believe that they expose users to smaller, less harmful doses of the disease that trigger an immune response.
This unproven theory suggests that face masks could help inoculate people while we wait for a vaccine.
Non-medical fabrics or disposable masks have been recommended around the world, primarily as a way to help prevent infected people from spreading the new coronavirus.
While they do not offer complete protection, masks can potentially reduce the amount of virus inhaled by a user, according to a recent article published this month in the prestigious New England Journal of Medicine (NEJM).
“We presume that the higher the dose (or inoculum) of virus that enters your body, the more you get sick,” Monica Gandhi, an infectious disease specialist at the University of California, San Francisco, told AFP.
“We believe that the masks reduce the dose of virus that is inhaled and thus increase the rates of asymptomatic infection.”
Gandhi, director of the UCSF-Gladstone Center for AIDS Research, said the asymptomatic infection was linked to a strong immune response from T lymphocytes, a type of white blood cell, which can act against Covid-19.
“We think that the masks can act as a kind of ‘bridge’ to a vaccine by giving us some immunity,” he said, adding that the researchers were launching several studies to test and test the theory.
These would include analyzing whether the requirement for a mask in certain cities had reduced the severity of illness there.
They are also studying antibody studies in Taiwan, where masks are ubiquitous but there are very few restrictions.
“Of course, it is still a theory, but there are many arguments in its favor,” Bruno Hoen, director of medical research at the Institut Pasteur in Paris, told AFP.
He said that we should “look at the use of masks in a different way”, which initially the health authorities considered unnecessary, in a context of scarcity.
Today, they are widely recommended to slow the spread of infection.
– Lessons from smallpox –
The theory echoes “variolation,” a rudimentary technique used before the advent of vaccines that involved giving people a mild disease to try to inoculate them against more severe forms of a disease.
In Asia, early variolation often meant blowing dry scabs from smallpox patients down the noses of healthy people, according to the U.S. National Library of Medicine.
When it came to Europe and America in the 18th century, the practice, sometimes killing the patient, commonly involved inserting smallpox under the skin.
The NEJM article suggests a parallel in the idea that being exposed to small doses of the virus increases immunity.
“It’s an interesting theory with a reasonable hypothesis,” Archie Clements, vice chancellor of the Australian Curtin University School of Health Sciences, told AFP.
But others expressed reservations.
Angela Rasmussen, a virologist at Columbia University in New York, said she was “quite skeptical that this was a good idea.”
He noted that we don’t yet know if a lower dose of virus means milder illness.
We don’t know if masks reduce exposure to the virus, he said on Twitter, adding that the duration and level of immunity are also poorly understood.
“This is an interesting idea, but there are too many unknowns to say that masks should be used as a tool to ‘variolate’ people against SARS-CoV-2,” he added.
A key obstacle to answering these questions is that the UCSF researchers’ hypothesis is difficult to test.
“It is true that such a hypothesis in humans using gold standard methods (of experimental design) can never be tested since we cannot deliberately expose humans to the virus,” Gandhi said.
But some studies have been helpful, he said, including research conducted in Hong Kong on hamsters.
The scientists simulated wearing a mask by placing one between the cages of the infected and healthy rodents.
They found that hamsters were less likely to get Covid-19 if they were “masked,” and even if they did catch it, their symptoms were milder.
There have also been some accidental experiments in the real world.
In one case, a cruise ship that left Argentina in mid-March sent surgical masks to everyone on board after the first sign of infection.
The researchers found that 81 percent of those who contracted the virus were asymptomatic, which Gandhi said compared to around 40 percent on other ships where masks were not routinely worn.
© 2020 AFP
