Masks are going to be mandatory – we need clear messaging now to ensure it happens | Daniel Howden

On 24 July it becomes compulsory to wear face masks in shops and supermarkets in England. What determines how we can expect such measures to play out? Largely, three things: how confident we can be in the available evidence, the size of the estimated effect among a compliant population, and the degree of compliance.

While a lot of attention has focused – rightly – on the first two of these, the third is equally important. Compliance not only encompasses questions of whether there is adherence to the guidance, but also the quality of the adherence. It is instructive, then, to compare the case of face masks with that of another very recent public health intervention: the recommendation of handwashing to stop the spread of Covid-19.

Handwashing is simple for most people. It is relatively cheap, and the means required to comply with the request – soap, running water – were largely already available in March, when advice on doing so began. While prior knowledge on handwashing existed, public health campaigns emphasised how best to do so, with simple messaging – “sing Happy Birthday twice” – combined with regular social media and TV campaigns providing more detailed advice.

Wearing a face mask is a more complex and costly act, and less familiar. People will face various difficulties in complying. Assuming that any positive effect of making masks mandatory exists, it is vital that these benefits are maximised and any potential downsides mitigated. This raises many additional questions. What sort of masks should be worn? How should they be worn? How often can they be worn? How often do they need to be cleaned? Is it more important to emphasise mask-wearing for certain groups? Might it be sensible to not recommend mask-wearing for others?

All this means at least two things: first, we need a public information campaign that helps widespread, effective compliance. This must not say simply “wear a mask”, or bury the answers to these questions on a government website; it should make the guidance highly visible and clear to understand. The World Health Organization has produced infographics and films that provide a good template.

Second, compliance needs to be possible for everyone. This crisis, and actions taken to mitigate it, has already had a devastating financial impact on many people. The price in a supermarket for a disposable face mask is about 70p: that cost has to be multiplied by the number of daily trips on public transport where masks are already mandatory – and, in one week’s time, will be multiplied by the number of visits to a shop or supermarket. While fabric masks are available, they need to be washed regularly – the WHO says at least once a day – adding more costs. Face masks are already being given away for free at some Network Rail-operated train stations: this could be rolled out more broadly, to other public transport hubs and at supermarkets.

The face mask has become something of an unlikely culture-war symbol, whose evidenced benefits are being exaggerated by some of its proponents and whose imposition is feverishly seen as barely a step away from the actions of a totalitarian state by many of its opponents. But concentrating now on whether face masks should be mandatory is to miss the most pressing point.

Subject to several exemptions, masks are being made mandatory in shops in England. To continue a proxy war on political or cultural issues – be it Brexit or anything else – into the arena of public health should be unconscionable.

This is a debate that, in practical terms, those in favour of masks have won. While there should be subsequent reviews of this policy, a government about-turn ahead of 24 July is extremely unlikely. And so we should demand that they be mandated in a way that means that any health benefits which may arise are maximised and any potential health costs minimised.

This makes necessary an extremely visible and easy to understand public health campaign, laying out the merits, rules and requirements of wearing face masks in public. Ideally that would have started a month ago, but that ship has sailed, so at the very least, it needs to start right now. It also means ensuring that the costs of compliance don’t take the greatest toll on people in lower income brackets. Those who have insisted on the introduction of face masks also have a responsibility to demand both of these things.