Face masks prevent Covid infections. At least we think they do. The actual evidence has been sketchy, based on old studies from other infectious diseases, lab tests done with petri dishes rather than live patients, and studies that were generally not rigorous or large.
It seems logical that masks would work. Covering one’s mouth and nose to prevent a virus getting in makes sense. And it’s the law that we use them in certain settings. But are face masks actually proven to prevent Covid infections? And if they are, exactly how effective are they?
Until now we haven’t had a big, real-world, randomised, controlled trial to answer that question. But now we do.
Last week a preprint study was released which looked at 340,000 patients randomised into two groups: one got free masks, education on how to use them, and encouragement from respected community leaders. The other group didn’t get any of these things.
The first group tripled its use of masks. Their rates of Covid infection dropped. The results were big: for every 2.5% increase in face mask use, the overall rate of symptomatic Covid infection went down by 1%. For over 60s the effectiveness was roughly triple this.
Face masks might be the magic bullet we have been looking for. Face masks are more effective at preventing illness than the other things we know work: physical distancing, social bubbles, hand washing, and staying home when sick. Face masks are also, of course, more effective than all the things that we know do not work: ivermectin, vitamins, and bleach injections. Face masks are the foundation of any Covid strategy. Face masks are a robust intervention: even if vaccination fails and a resistant variant spreads, there is no reason to think that masks will not continue to be very effective.
The authors from Yale, Stanford, Berkeley, and Deakin universities along with their colleagues in Dhaka, Bangladesh, credited the success of their face mask interventions to three things: the masks were free, were provided alongside education on hygiene practices like physical distancing, and were strongly supported by respected members of the community: clergy, elders and other village leaders. That last one, to my mind, is the key: to the average person seeing someone they know, respect and trust wearing a mask makes an enormous impact.
This huge international study also showed that surgical masks, those blue masks you can buy in most any supermarket, were roughly twice as effective as cloth masks in preventing Covid infection. This fits with prior studies’ results. And while physical distancing increased marginally after the hygiene education, it was mask use that was responsible for the lion’s share of the drop in cases.
The study also supported the well-known risk posed by crowding in houses of worship: unlike in the markets, where distancing increased, in houses of worship physical distancing was ignored despite the educational intervention. A tradition of shoulder-to-shoulder prayer couldn’t be changed, but the protective effect of mask wearing seemed to counteract this. And role-modelling made the difference.
A religious leader wearing a mask might be one of the most effective anti-Covid interventions that exists. One wonders if the converse, a religious leader refusing to wear a mask, might therefore be one of the more virulent factors in supporting Covid spread.
The study analysed many different variations of these interventions. Things that were found not to work included providing some communities’ leaders with incentive payments for compliance, texting people with frequent hygiene reminders, and putting up signs and advertisements supporting mask wearing. Seeing someone you ‘know and trust’ wearing a madk seemed to matter greatly.
This study suggests showing our trusted and respected local leaders wearing face masks at work, school, in sport, and in our houses of worship is something we should highly prioritise in our anti-Covid campaigns, along with providing masks to New Zealanders free of charge. Simply put, face masks appear to be our most effective anti-Covid intervention. And seeing them on the faces of our local leaders makes a difference.