With a number of countries moving to ease lockdown restrictions, face masks are becoming the new norm. In Austria, people now have to wear face masks when shopping. In Germany, vending machines at train stations are being stocked up with masks in a bid to help curb the spread of coronavirus among commuters.
Officials in the UK, though, have stopped short of recommending widespread use of face masks. Until now. On April 28, Scotland’s first minister Nicola Sturgeon advised the Scottish public to wear face masks in public spaces where space is too limited to follow social distancing rules.
Across the world, face masks are increasingly viewed as a step out of lockdown, with some countries mandating them in public. Despite Sturgeon’s recent comments, the rest of the UK still isn’t following suit. So what gives? It’s a complicated and controversial question. There have been concerns that people will rush to buy medical-grade masks causing the NHS to face even greater supply shortages, and that masks could create a false sense of security and lead to a lapse in social distancing. It is also unclear whether or not face masks actually protect individuals against the novel coronavirus.
But emerging evidence suggests the benefits may outweigh the risks. We now know that people are infectious before symptoms of the Covid-19 disease start to appear, and some never show any symptoms at all. In a report from April 23, researchers from Imperial College of London pointed out that around 40 per cent of infections among healthcare workers seems to occur before symptoms set in. So the argument is that, rather than protecting healthy wearers from infection, face masks could prevent carriers who are either asymptomatic or minimally symptomatic from unknowingly spreading the virus to others when coughing, sneezing, or during a conversation.
The problem is that testing the efficacy of face masks is no easy task. Randomised control trials – where one group has the intervention being tested and the other receives an alternative intervention, a placebo or no intervention at all – are the gold standard for studying causal relationships. But while it is possible to control confounding factors in a laboratory, randomised control trials tend to produce little evidence of effects when done on people in their households or in public.
Julii Brainard, a senior researcher in health protection at the University of East Anglia, and her colleagues looked at 31 published studies about how well face masks protect against influenza-like illness and found poor compliance in most studies conducted as randomised control trials. That is because participants who were supposed to wear the masks often didn’t wear them and people who weren’t supposed to wear them did, which skewed the results.
“Part of the reason why the research has been so difficult is that what should be our best-quality experiments aren’t very good. So we’re then stuck with what are called observational studies where researchers ask people what they did,” says Brainard. In households where an infected person and their housemate both wore masks, the healthy members of the household were indeed 19 per cent less likely to become ill. There are however many transmission paths for viruses within a household, says Brainard, which makes it difficult to work out where and how someone may have caught an illness or not.
The scientific debate over the use of face masks to prevent the spread of coronavirus is also revealing a double standard, says Babak Javid, a professor at the Tsinghua University School of Medicine in Beijing and a consultant in infectious diseases at Cambridge University Hospitals. Despite the lack of trials looking at how different hand-washing practices stop the spread of coronavirus, governments and health institutions still advocated the 20-second rule. “There have been similar sorts of [laboratory] studies for hand washing, and they’re equally disappointing,” he says adding that there have also been no trials to test the two-metre social distancing rule in public.
Besides the traditional masks used by health workers, researchers have put homemade masks made from cotton, nylon and other fabrics to the tests in lab experiments and heavyweight “quilter’s cotton” with a tight weave has proved particularly effective at filtering out small particles. “That kind of makes sense. It even makes more sense than washing your hands because [Covid-19] is a respiratory infection,” says Javid. Infected people spread coronavirus through contaminated droplets from their nose or mouth, which then may land on surfaces around them.
Javid argues “natural experiments” suggest at least a correlation between mask-wearing and reduced transmission of the novel coronavirus. Jena was the only German city to have imposed face masks by March 31 and it recorded no new infections in the following eight days, while surrounding cities continued to see a rise. The Czech Republic was the first country in Europe to mandate face masks in public on March 18. While the number of new daily infections and deaths continued to climb for another three weeks, the relative growth rate there slowed down compared with neighbouring Austria, Germany and Poland. “They’re very similar places, have otherwise similar public health measures, and they are seeing different rates of growth of the disease. The only apparent difference seems to be the face mask. I think that’s more compelling for me than comparing Asia with Europe,” says Javid.
The widespread use of face masks might also serve a symbolic function, as it has in many Asian countries where wearing masks has long been culturally acceptable. As Ed Yong notes in The Atlantic, healthy individuals could signal to others in society that they are taking the coronavirus pandemic seriously by wearing face masks in public and that they are poised to protect them from possible infection rather than themselves.
Taking the scientific limitations into account, Brainard’s review of 31 studies found that face masks can be protective for vulnerable individuals when worn for short periods of time, particularly in crowded environments such as on public transport or in shops where it is difficult to stay two metres apart. Wearing masks for hours at a time in office spaces, for instance, would however not be practical as people will slip into their usual habits and have to take them off to eat.
The UK government’s scientific advisory group for emergencies (Sage) met on April 21 to review the latest evidence and may make new recommendations in the coming weeks. “It’s quite conceivable that they will recommend something like wearing masks in crowded places where you can’t keep two meters apart,” says Brainard. “I could see there being a much more supportive position on it.”
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