COVID-19: masks for the general public? yes or no?

  • Edna Astbury-Ward, Medscape.com

  • UK Medical News
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UK medical and scientific experts on the SAGE (Scientific Advisory Group for Emergencies) committee have assessed the current evidence on whether the general public should be advised to wear face masks. However, the Government hasn’t yet announced the outcome.

There are concerns a rush to buy masks could divert supplies away from the NHS. 

The Surgeon General of the United States went on TV to show Americans how they can make their own improvised facemask from an old t-shirt and a couple of elastic bands. Everyone from Louis Vuitton to small artisan dressmakers in rural areas has been rushing to their sewing machines to make facemasks. Yet very little good quality research exists on the use of cloth masks, especially in non-medical settings. Neither the World Health Organisation (WHO) nor Public Health England (PHE) has declared a position on mask-wearing by the public. So the UK general public remains unclear about whether or not to use face masks during the COVID-19 pandemic.

Expert Opinions

However, several UK experts have been giving their views. Professor KK Cheng, director of the Institute of Applied Health Research at the University of Birmingham, has said: "In fact, there are strong mechanistic reasons for covering the mouth to reduce respiratory droplet transmission. If it does not work, why do we ask people to cover their mouths when coughing or sneezing?"

Professor Ian Jones, professor of virology at the University of Reading, argued that anything that reduces droplets entering a person’s mouth, even if some droplets do pass through the mesh, is helpful to some extent. He said, "If an aerosol droplet hits the weave of the mask fabric rather than the hole it is clearly arrested. And lessening the aerosol dose chips away at the R0 [reproduction number] and helps to slow the epidemic . . . They are not a cure but they address the longer flatter epidemic curve everyone is trying to achieve."

Timely Advice

It is timely therefore that Professor Trish Greenhalgh, professor of primary care health sciences, Nuffield Department of Primary Care Health Sciences, University of Oxford, took part in the Royal Society of Medicine (RSM) webinar series on COVID-19, one episode of which was devoted to policymaking on masks for the general public.

The session was chaired by Professor Sir Simon Wessely, professor of psychological medicine at King’s College London, president of the Royal College of Psychiatrists, and a consultant psychiatrist at King’s College Hospital and at the Maudsley Hospital.

Sir Simon famously protected himself from catching coronavirus from his wife by using his Chelsea FC scarf (although one listener was heard to declare that would be sufficient for anyone to practice social distancing).

This week there have been a number of announcements on the matter, with more expected by the weekend. Medscape UK has looked at the information available on the subject and reports the outcome of the RSM webinar and various expert opinions.

The Precautionary Principle

The US Centres for Disease Control and Prevention (CDC) has advised all Americans to wear cloth masks in public to prevent the spread of COVID-19, but what about the UK?

The BMJ has reported that the evidence is not sufficiently strong to support widespread use of facemasks as a protective measure against COVID-19. However, there is enough evidence to support the use of facemasks for "short periods of time by particularly vulnerable individuals when in transient higher risk situations".

Transient higher risk situations have been described by Prof Greenhalgh and others as buses, trains, underground, supermarkets, pharmacies and any other places where social distancing cannot be easily maintained. Prof Greenhalgh advocated for widespread mask-wearing, drawing an analogy with the 'precautionary principle' and suggesting that we should sometimes act without definitive evidence, just in case. She argued that in the face of a pandemic, the search for perfect evidence on the matter may be the enemy of good policy. 

Prof Greenhalgh said: "It is time to act without waiting for randomised controlled trial evidence." She is not alone in her views. Prof Sian Griffiths, emeritus professor, Chinese University of Hong Kong, and co-chair of the Hong Kong government’s SARS inquiry, said: "The scientific debate on effectiveness is between different approaches to assessing how effective masks are at stopping infection, particularly in community settings… in the UK we await further updates from ministers when they have reviewed the latest evidence."

Some experts are concerned that the new policy will be introduced before the UK public are fully aware of how to use masks correctly. Prof William Keevil, professor of environmental healthcare, University of Southampton, said: "If wearing a mask becomes common, then the wearer must recognise that they must not keep touching the mask (because if it is loose-fitting then it moves around or irritates the skin)." He added that if governments are going to endorse wearing masks then there must be "an immediate education programme to show the general public how to choose the best quality masks, fit them correctly, wear them for a recommended length of time in a crowded environment and safely dispose of the mask, followed by washing hands".

Lack of Scientific Clarity

During a lively debate at the RSM Webinar on the subject of mask-wearing, Professor Greenhalgh said: "If we take the view of evidence-based medicine, then what we really need is a large randomised controlled trial, preferably a meta-analysis with all the experimental evidence stacking up, that gives a definitive answer that we've done this ‘big experiment’. But, I would say, we need to put aside the traditional hierarchy of evidence, because I don't think we need to hang our hats on big randomised controlled trials right now."  She commented that it was a fairly simple fact that if you cover your nose and mouth when coughing and sneezing that some of the droplets will be prevented from spreading and that there was the likelihood that cloth face coverings would help prevent droplet spread.

Prof Greenhalgh argued against what she described as the ‘Straw Man Theory’ "that if we all wear face coverings then we would suddenly behave irresponsibly in other ways, we would stop washing our hands, we'd go around, hugging people and getting really close to people". She added: "Many people can be taught to use masks properly and will do this consistently without abandoning other important anti-contagion measures."

Mixed Messages

Sir Simon posed the question to Prof Greenhalgh that it is still fairly uncommon to see people in face masks in the UK, compared with other countries, and asked her if there was "more cultural resistance to them in the UK?" She replied: "I think the reason why people are not wearing face coverings is they're getting mixed messages. Different people are saying the evidence is there, the evidence is not there, so I'm not surprised; I wouldn't blame anyone at the moment for not taking action on face masks."

A round-up of the information available to date and an analysis of all the available expert opinion suggests there are four key reasons given against wearing masks (none of which have been either proved or disproved):

  • There is limited evidence of the efficacy of mask-wearing

  • People are unlikely to wear them properly or consistently

  • Wearing a mask might make people feel safe and hence disregard other important public health advice such as hand washing and social distancing

  • Public buying could lead to major supply chain problems especially for key workers

Adapted from Medscape UK.