The masks work. Get over it.

Social media has been buzzing this week for a new study from Denmark on the effectiveness of masks on the risk of contracting Covid-19. Depending on the news source you looked at, you may have heard that masks may not protect the people who wear them or that wearing masks does not prevent the spread of the virus. You may also have read the almost immediate backlash where scientists pointed out all the evidence that masks actually work.

I read the study. It proves nothing, as even its own authors admit.

Let’s break down the actual results just a little to see what it is all about.

The study was conducted in Denmark in April and May of this year and what it tried to do (not very effectively) was to measure the effect of a recommendation wearing masks. That’s right, they were not directly measuring the benefits of masks!

The study enrolled around 6,000 volunteers, and half of them recommended wearing masks whenever they went outdoors. They also provided masks for those volunteers. For the other half, they did nothing. At the time (March and April), Denmark recommended social distancing, but wearing a universal mask was not recommended.

Quite a few people withdrew, so in the end they only had 4862 people in the two groups, about 2400 per group.

What did they measure? Well, they did an antibody test (far from perfect, but let’s not digress) in early June to see whether or not people were infected with SARS-CoV-2, the virus that causes Covid-19.

(Note that they did NOT measure how well the masks could protect anyone else in the community. They were just measuring whether a mask could protect the wearer.)

And the results? 42 people in the mask recommendation group were infected and 51 people in the no-recommendation group were infected. (That’s 1.8% versus 2.1% for each group.) So there was a small reduction, but it wasn’t statistically significant, meaning we can’t really say if the mask recommendation helped. to prevent infection.

The study authors themselves admitted this, writing: “the results are inconclusive … compatible with a 46% decrease up to a 23% increase in infection”. In other words, the results could mean that masks reduce self-infections by 46% or increase them (bizarre as it sounds) by 23%.

In other words, this experiment does not tell us much. If it wasn’t Covid-19, I doubt the Annals of internal medicine I would have published it. (A comment of my colleagues at Hopkins and Stanford suggested the Annals he was right to publish it, provided that scientists “carefully highlight the questions that the trial answers and does not answer”.)

Now some big caveats. First, in the mask recommendation group, only 46% of participants wore masks as recommended. Second, the study did not ask if anyone in the non-recommended group wore masks. Third, the study relied on self-reporting to determine who actually wore their masks consistently – that is, they simply asked participants to tell them how often they wore their masks.

What? Imagine studying the use of seat belts to reduce injuries and only 46% of the people you told to wear seat belts wore them correctly. Also, imagine relying entirely on self-reporting to determine who actually wore the seat belts. This study project is almost useless if you want to know the true benefits of seat belts.

So the study on the Danish mask was inconclusive, as its own authors report. Therefore it would be a huge mistake, scientifically speaking, to take this non-result and conclude that the masks do not protect you. It would be an even bigger mistake to conclude that the study showed that masks do not benefit the community. Unfortunately, that didn’t stop these two Oxford University scientists from jumping to exactly that conclusion. They stated, in an article in The spectator, which the study showed that “wearing masks in the community does not significantly reduce infection rates.” This is completely wrong. The study did not even measure infection rates in the community.

(For an excellent Twitter take on what the studio does not try, see this thread from The Health Nerd.)

And as the CDC has documented, numerous studies have already shown that masks are very effective in limiting the spread of Covid-19. And a study last summer pointed out that increasing mask use by just 15 percent “could prevent the need for blockages and reduce associated losses by up to $ 1 trillion” in the United States alone. So yes, it’s a good idea to wear a mask.

It is also simply common sense that if you wear a mask, the amount of virus you breathe or outside will be reduced. You are not only protecting yourself, you are also protecting everyone around you.

Until we can keep this pandemic under control, we must all wear masks in public. It is absolutely ridiculous that this has become a political issue, as it has in the United States. For those who think that wearing the mask somehow limits their personal freedom: overcome it. When you see a red light at a busy intersection, do you run through it because you need the “freedom” to drive like crazy? No. Civil society requires everyone to follow some basic rules to protect each other, and wearing a mask is one of them during a pandemic. And who do you think that wearing a mask somehow shows their civic virtue? No, this is also wrong. To use the same example, stopping at a red light does not prove that you are virtuous.

It’s just a mask. It is not a political statement. Get over it.