In the year of COVID-19, many things that are really scientific questions have become absurdly politicized. There’s hydroxychloroquine, which as an anti-malarial drug really shouldn’t be the topic of much political conversation, but somehow is. There’s herd immunity, which has gone from a fairly niche epidemiological concept mostly discussed by experts to one of the most political topics in the world.
And, of course, there’s masks, which have somehow become arguably the key political battle in the COVID-19 war.
This is very strange, because ultimately wearing a mask is arguably the easiest way to reduce your risk of COVID-19 infection. While the benefits of mask mandates — especially those that only target public, open areas — are perhaps more debatable, at an individual level the idea that a mask should be an extreme political choice is really just bizarre.
And now a new study has dropped into this tumultuous dialogue. Danish researchers have published the first large, randomized trial of mask wearing that apparently shows that masks don’t work for COVID-19. Denialists everywhere are celebrating, which is again very odd because masks are arguably the only intervention against COVID-19 that doesn’t require restrictive rules and business shutdowns.
Unfortunately for the denialists, of course, this study doesn’t say anything of the sort. They didn’t find any benefit for masks, but that doesn’t mean that we can say that masks don’t work.
Confused? Let me explain.
The study in question was called DANMASK-19, and was a fairly simple randomized-controlled trial in Denmark looking at whether giving people masks and telling them to wear the masks could prevent COVID-19 in those people, on top of lockdowns and other social distancing measures. They found that, after one month, there was no statistically significant difference between the mask and non-mask group in the study.
Cue the ridiculous tweet-storm from people delirious with joy that they no longer had to wear thin cloth on their faces for up to minutes at a time.
The thing is, the study didn’t actually answer most of the important questions that we have about masks. It really meant nothing at all to almost anything that we actually want to know about masks, because it wasn’t designed to tell us whether, for example, we should enact mask mandates in public places or not, or whether a mask would reduce your risk of infection if you wore it correctly whenever you were around other people.
What the study was designed to show, specifically, is that when a country is in lockdown and/or under significant social distancing restrictions, advising people to wear masks and providing them with masks does not reduce their risk of getting COVID-19 by more than half. That may sound finicky and specific to you, but it is also literally the only thing that the study was constructed to show us.
Some things that the study didn’t, and couldn’t, tell us:
— Whether mask mandates are useful
— Whether you should wear a mask
— Whether masks prevent less than 50% of infections
— Whether masks could be effective outside of lockdown situations
— Whether public health policy should include masks
And on, and on. Indeed, given that the study took place while Denmark was largely in lockdown, it’s hard to say what it means for situations where social distancing laws are less severe. The study was also very underpowered to detect any effect smaller than 50% — basically, you need truly enormous numbers of people to find a statistically meaningful reduction in infection rates if only 2% of people are getting infected in your study. For some context, to know whether masks reduce the risk of infection by 20%, the study would’ve had to recruit about 240,000 people, or 40x the number that they did.
It’s also important to note that this didn’t test whether masks prevent infection themselves. The researchers told people to wear masks, and gave them masks, but many people still didn’t wear them. In fact, less than half of the people in the mask group actually wore the masks as advised, which is really not a lot.
So where does that leave us in terms of masks?
The unfortunate fact is that this study basically doesn’t change the evidence around masks at all, despite what the denialist crowd have been saying. In fact, the lead author of the research has publicly stated that you should wear a mask if possible, because while their research indicates there is not a huge benefit to individuals, even a tiny reduction of infection at the individual level can be meaningful to the population.
And really, that seems to be the main take-home here. Even if there isn’t a huge benefit to you individually from a mask, if infection numbers are incredibly high and rising in your local area then every little helps. At this late stage in the pandemic, mask production is through the roof and it’s unlikely that you’ll be taking one away from someone in need, especially if you get a reusable one. On a day when about 1 in 50 people in the entire United States currently has COVID-19, and 1 in 4,000 people are currently hospitalized, the cost-benefit of wearing a mask leans very heavily in favour.
Yes, the benefit to you is unlikely to be large. But that’s the story of every public health intervention — it’s rare that the main benefit will be for you as an individual. Most of public health is trying to get people to act as a group when only a relatively small number of them will directly benefit, and masks are no different.
Ultimately, the reality is that when you’ve got an accelerating epidemic that has killed hundreds of thousands in the U.S. alone, any little helps. Masks probably won’t reduce your risk of infection by 50% or more, but it’s not unlikely that they could reduce it by 20%, which in context may be extremely beneficial at the population level.
And don’t believe the hype.
The new mask study really didn’t tell us much at all.