Earlier this month, the Toronto Star contacted medical officers of health in Ontario to see whether they would be wearing a mask in public once Ontario’s mandate ends Monday. My answer was “no,” but the Star reporter did not seem terribly interested to hear my rationale.
Of course, important information can sometimes be gleaned from statistical investigations of what has happened naturally, (we call these studies observational rather than experimental) but these are prone to bias and subsequent contradiction. Is it that flossing your teeth halves the risk of heart disease? Or is it that people who don’t floss have other habits that cause heart disease? For decades, the question was argued in medical journals and the popular news media. Experiments show no link, and so the skeptics are validated.
Conversely, it was first determined that cigarettes cause cancer by looking at rates of lung cancer in non-smokers versus smokers. A famous 1950 BMJ paper showed that doctors who smoke were ten to thirty times more likely to die of lung cancer than those who do not. However, it took subsequent animal experimentation to convince the public of the link. It would be unethical to experimentally subject humans to cigarette smoke, but we now have experiments of smoking cessation that show reduced lung cancer in humans. The link has been found to hold at every level of scientific evidence; there really is no room for skepticism.
Overwhelmingly, the skeptics who wait for randomized trials before believing in a medical intervention have been proven right more often. It is only in situations, as with cigarettes, where the correlation is very strong and very dire where I would be tempted to believe otherwise.
A massive RCT of masking called the DANMASK trial investigated the question of whether a person could prevent themselves from getting COVID by wearing a mask in public. It did not show an effect. The study was heavily criticized because it only looked at the personal health effects of personally masking. It did not look at the community-wide effects of asking a whole community to mask.
There have been many observational studies of community masking on COVID-19 transmission in humans. Sadly, after two years of pandemic, there has only been one RCT. The study was performed by researchers from Yale and Stanford in Bangladesh. Fortunately for us, it was monumental in scope, randomizing 300 villages to intensive community masking promotion and 300 villages to the status quo.
They found little to no effect on COVID-19 transmission from the use of cloth masks. They found a small benefit, 11 per cent decrease in transmission, from the use of surgical masks. Surgical masks prevented Covid cases in adults over 50 but showed little effect in adults under 50.
The authors do allow that with universal masking there could have been a greater reduction in transmission, but that doesn’t detract from the fact that cloth masks were of almost no benefit and that where surgical masks were used, age was the determining factor.
Frankly, this is very underwhelming. By way of comparison, initial RCTs of COVID vaccines showed that they reduce transmission by 95 per cent. The effect has since waned, but they still reduce the risk of hospitalization or death by about 90 per cent. A booster dose reduces the risk of transmission by about 50 per cent.
Notably, the Bangladesh study was performed over the winter of 2020, when vaccination rates were roughly zero, and test positivity was very high (10-15 per cent). Currently in Ontario, all adults have had more than ample opportunity to get three if not four doses of vaccine. Of the 10 per cent who have not availed themselves thereof, a high proportion have since been infected and now have robust natural immunity. The marginal benefit of community masking observed in the Bangladesh trial is likely to be even more marginal in present-day Ontario.
At the beginning of the pandemic, we were told by experts that face masks would not be effective at preventing Covid-19 infection. At Kingston Health Sciences Centre, where I worked, administrators went so far as to order medical residents not to wear masks around the hospital.
It has always seemed to me that some sorts of face masks would be beneficial in some situations for some people. Extremism on either side, “face masks don’t work,” or “everyone should wear a face mask at all times” was unlikely to be validated by science.
Many self-styled “experts” are demanding mask mandates be reinstituted in Ontario. We need to be very careful. In modern medicine, our knowledge base is founded on RCTs. At present, the best evidence we have suggests that cloth masks are of almost no value and community masking is of little value to individuals under 50. Anyone who promotes a return to cloth masking or masking for the sake of children would appear to be out of touch with this knowledge base and therefore, definitionally, not an expert.
I will wear a high-quality clinical face covering when I interact with high-risk individuals in high-risk settings. For the most part, this will be in the hospital. If I am feeling sick or recently came into unprotected contact with a COVID patient, I will stay home.
Otherwise, I am looking forward to smiling at students, coworkers, and store clerks again.
Matt Strauss is an ICU physician practicing in Ontario. He is the acting Medical Officer of Health for Haldimand-Norfolk.