Can masks really help to prevent the spread of COVID-19?

I don’t really get the whole ‘anti mask’ thing. But many kind people on Twitter and elsewhere have been attempting to correct my poor understanding of the effects of mask-wearing, after a recent blog post of mine. That blog post was mainly about statistics being used to bamboozle but I seem to have tapped into a large pool of mask-resentment.

My new friends and correspondents have provided me with lots of shiny data to ‘show’ why masks don’t work. This can be boiled down into two types:

• papers from journals about the effectiveness of masks against influenza

• graphs showing a rise in cases of COVID-19 even after mask-wearing has been made obligatory.

For the latter, I don’t think that anyone is claiming that masks will stop waves of infections spreading through a population. What masks may do is to reduce the overall numbers of people with the infection.

For the former, we need to be careful extrapolating from one disease to draw conclusions about another. SARS-CoV-2 and flu viruses are very different in nature.

There’s another factor here to, in that many studies on masks do not just look at masks; they look at combinations of masks and other preventative strategies. Many of the studies are also done in communities rather than in lab settings, and so it is impossible to monitor how strictly people adhere to mask-wearing protocols. Unpicking all of this to draw a conclusion about masks is tricky.

The other thing to point out is that, contrary to popular opinion, the methods by which COVID-19 is transmitted is still an active field of research. We still aren’t sure of all the ways in which the virus can be transmitted from person to person.

However, as the pandemic has progressed, more and more studies have been done on transmission prevention and COVID-19; we no longer need to rely on extrapolation because we now have COVID-19-specific data. And a lot of the unpicking of this data and systematic analysis of the current research on masks has usefully been undertaken by Howard et al. Their paper was published in January in PNAS - Proceedings of the National Academy of Sciences of the United States of America (a highly respected scientific journal). The link is below.

The paper’s conclusion is that “nonmedical masks have been effective in reducing transmission of respiratory viruses; and places and time periods where mask usage is required or widespread have shown substantially lower community transmission.”

The evidence in favour of wearing a face mask to protect yourself from COVID-19 is actually not particularly strong. However, the evidence in favour of wearing a face mask to protect others from you is much stronger. Given that many people can be totally asymptomatic with COVID-19 and many others do not have symptoms at the start of infection, this is what the focus should be on. Forget about it being PPE and think of wearing a mask as CPE (Community Protective Equipment). So, for me, if wearing a mask is going to save just one person from getting a severe life-changing form of COVID-19, then I’m going to wear one (no matter how convinced I am that I don’t have COVID-19).  

The other encouraging point from all this research is that most face coverings are almost as effective as N95 respirators. It also seems that masks in general are much more effective in preventing COVID-19 transmission than they are at stopping the spread of influenza viruses.

Even so, mask wearing is not going to be the complete and only answer. Mask-wearing on its own does seem make a contribution to preventing community spread of COVID-19 but it has to be used with other protective measures.

Back to my new friends on social media. The anti-maskers seem to come in four varieties:

• those who don’t believe the virus exists and it’s all a big hoax

• those who think that masks harm your health (by trapping carbon dioxide etc.)

• those who don't believe they work so don't think people should wear them

• those who object to the loss of civil liberties in being made to wear a mask.

And a fair summary of my responses are:

It’s a hoax

• The hoax idea doesn’t work for me, and that’s the subject for a different blog! But (a) I can’t understand why any government would want to ruin their economy for the sake of making their citizens live in fear, (b) when it takes governments from different countries years to agree on the simplest of things, I can’t really see how all the governments across the world have suddenly agreed on this and (c) if it’s not SARS-CoV-2 that’s responsible for the 100 000 excess deaths in the UK in the last year, then I’m very scared of whatever unknown phenomenon is doing this.

Masks damage your health

• There's lots of evidence that close-fitting respirator masks do trap a certain amount of heat and carbon dioxide (much like being in a stuffy room) and can increase heart rate.

However, loose fitting surgical masks or homemade masks made out of rubber bands and an old T-shirt do not suffer from these problems. Surgeons wear surgical masks all day, and you don't find them dropping like flies from doing so. (Oh, and before anyone mentions it ... there are surgeons that have asthma too.)

Masks don’t work

• I was a mask sceptic. I remember about a year ago chatting to my friend Ana about this. I wasn't convinced that they made a lot of difference to viral transmission. Then some evidence came out that, in a public setting, they did have some effect. I have now worn a mask every time I have been out since last March. As a scientist, my views and opinions change with the evidence … I try not to fall into the trap of finding evidence to fit what I think must be right.

It’s taking away my civil liberties

• Many of my civil liberties are constrained by society and laws. I cannot, for example, go to Sainsbury's without any clothes on. In terms of civil liberties, I see no difference in being told to wear clothes than in being told to wear a mask. The difference is that the sight of my naked body is unlikely to kill anyone or give them a long-term illness. Or, I don’t think so anyway.

Generally, I'm very polite in my dealings with people who disagree with me. Freedom of speech is a privilege that many people around the world do not have, and I enjoy the intellectual aspect of having a debate and examining evidence.

However, on the subject of masks, I really do wish that some people would just wise-up and put a bloody mask on, rather than continually bleating on about how this is affecting their ability to live.

The countries that beat this pandemic first are the ones where citizens play as a team. In any team, not everyone will agree with the team captain or the manager in terms of tactics. However, players in any good team will accept the decisions (even if they voice their own unhappiness). The teams that fail are those that contain players who do not understand the basic concept of a team.

Howard et al. 

An evidence review of face masks against COVID-19

https://www.pnas.org/content/118/4/e2014564118

Text: Mark Levesley   @marklevesley    levesley.com

Photo: Alexandra Koch via Pixabay