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expert reaction to the Scottish government announcing that they now recommended people cover their faces while in some enclosed public spaces, such as shops and public transport

The Scottish Government have announced new recommendations that people cover their faces while in some enclosed public spaces, such as shops and public transport.


Comments sent on Thursday 30th April

Dr Antonio Lazzarino, Department of Epidemiology and Public Health, UCL, said:

“The question is not whether facemasks decrease or increase the spread of the coronavirus.  We don’t have a yes/no question here.  The questions is: by how much can they be protective and by how much can they be harmful?  This reasoning is routinely adopted for all drugs, instruments, equipments and surgical techniques we can use.  We must adopt it for face covers too.  Although we do not have enough time to quantify those effects in the appropriate way now, we must make hypotheses, as follows.

“By how much can face covers decrease the probability of infection?  By very little.  Face masks block the droplets, which are the big, visible, particles of saliva we may emit when we sneeze or cough or pronounce certain words.  For this virus to be so contagious, the main route of transmission must be via the smaller, invisible particles, which are not filtered by surgical masks or scarves or bandanas.  Therefore, trying to block the bigger particles gives a minor protection against the transmission.

“On the other hand, there are many possible side effects of carrying face masks.  The risks they give is likely to be higher than the desired protective effect.  These are described in my BMJ letter:


Comments sent out on Tuesday 28 April

Professor Robert Matthews, Visiting Professor in statistics, Department of Mathematics, Aston University, Birmingham, said:

[Comment on how evidence is being assessed on facemask use]

“The public may well be puzzled by the continuing lack of scientific consensus over the wearing of face masks by the public. Part of the reason is that rigorous assessment of their pros and cons is very challenging. Randomised controlled trials – usually regarded as the “gold standard” in assessing efficacy – are not necessarily ideal, as they may fail to reflect the problems of everyday mask use. While observational studies may do better here, they raise other issues, such as people exaggerating how diligent they were in using the masks.

“The studies that have been conducted are generally small, leading to substantial uncertainty about the size of the protective effect. Even when their results are pooled together, the outcome is often statistically non-significant.

“Worryingly, some major systematic reviews of the evidence have made the basic inferential blunder of interpreting non-significance as evidence of no effect. Non-significance means simply that a finding is so uncertain that it fails to meet a widely-used (and misinterpreted) standard of evidence. As such, it represents an absence of evidence of benefit, not evidence of its absence.

“In the case of studies of face masks, non-significance reflects the fact that most studies are too small to provide strong evidence either way. Taken at face value, systematic reviews actually suggest face masks could play a useful role in helping to move beyond lock-downs. Yet considerable doubt remains.

“It is regrettable that the inadequacy of the existing literature for resolving these doubts was not recognised much sooner. Then the seemingly endless – and often flawed – debate over its interpretation could have been replaced by a major research programme akin to that adopted for vaccines and anti-virals.

“This could identify materials and designs of face masks suitable for home production, in order to preserve supplies for health workers. Candidate designs could then be tested at accredited laboratories to assess efficacy, safety and suitability for use alongside existing countermeasures such as social distancing. 

“Governments are looking to the research community for guidance on ending the current lockdowns. What role, if any, facemasks can play is best addressed by a multidisciplinary research programme, not by trawling the literature.”


Prof Trish Greenhalgh, Professor of Primary Care Health Sciences, Nuffield Department of Primary Care Health Sciences, University of Oxford, said:

“The Scottish Government’s decision to support the wearing of face coverings by the lay public in shops and other public places is important and timely. As we all anxiously wonder how long lockdown is going to last and contemplate what the ‘new normal’ will be like after the first wave of covid-19, we should be reconsidering all measures that have a reasonable possibility of getting the country back on its feet again. 

“Face coverings are a common-sense way of reducing the transmission of viral illnesses by droplet infection. They are as evidence-based as school closures, handwashing and lockdown (i.e. none of these measures is supported by definitive randomised controlled trials but all are supported by other kinds of science).

“Over 50 countries are now recommending or requiring the wearing of face coverings by the public. Those who introduced this measure early flattened the curve early and have had far fewer deaths. There is not a single example worldwide where the introduction of face coverings for the public was associated with a worsening of national figures on new cases or deaths.

“The reluctance of our government’s scientific advisors to support this measure while at the same time supporting messages to “sneeze into your elbow” is surprising: face coverings are highly unlikely to cause harm and may well save lives.”  


Prof Linda Bauld, Bruce and John Usher Chair in Public Health, University of Edinburgh, said:

“I welcome this recommendation from the Scottish Government as it represents practical advice that the public should find relatively easy to follow. They have advised that people in Scotland should use a secure face covering, comprising washable fabric, to cover their nose and mouth in specific circumstances. This is on public transport and when shopping for essential food and medicines – or likely in future, in any other indoor settings where it is difficult to avoid other people. They’ve also made clear that there is no good reason to wear face coverings outside or in the home, and that there will be certain groups (children under the age of 2, those with conditions for whom it is not possible or appropriate) who don’t need to follow this guidance. 

“The evidence for the effectiveness of face coverings of this type in limiting virus transmission is very limited. However, in common with other public health measures, sometimes adding a small change on top of bigger changes (in this case, face coverings plus social distancing plus hygiene) can add up to more than a single measure. There is a risk that people won’t use these coverings properly – for example not washing them, taking them off and putting them on surfaces which would be counter-productive. But I do see more and more people in Scotland wearing them anyway. So our social norms are gradually shifting and it is likely that wearing one in certain circumstances will become part of the ‘new normal’ that we are all getting used to.”


Prof Sian Griffiths, Emeritus Professor, the Chinese University of Hong Kong, and co-chair of the Hong Kong government’s SARS inquiry, said:

“The use of cloth face coverings/masks has been widely debated. The general view is now that they are not a substitute for good hygiene measures or social distancing but they may contribute to reducing spread of infection as part of a public heath platform . This has been recognised by many other countries in Europe as they move towards releasing lock down as well as being routine practice in other parts of the world most notably East Asia .The key challenge is to make sure that those most in need , i.e. those caring for sick patients as well as those in situations where they are at risk such as older peoples care homes, are able to get the masks they need. This is why Scotland , in line with the US CDC , have recommended wearing a face covering. At the same time , the public need to be alerted to false reassurance that this will protect them from infection and need to maintain their awareness of the risk of Covid and need for mitigating behaviours.”


Prof Babak Javid, Principal Investigator, Tsinghua University School of Medicine, Beijing, and Consultant in infectious diseases at Cambridge University Hospitals, said:

“This is welcome news from the Scottish first minister with regards to use of face coverings in enclosed spaces where physical distancing may be difficult.  It should be re-iterated that for public wearing of masks to have appreciable impact on a population level, most mathematical models agree that more than 50% of people would need to comply.  I hope that the Scottish public will embrace this recommendation as an altruistic act that will benefit the population as a whole.”


Prof Keith Neal, Emeritus Professor of the Epidemiology of Infectious Diseases, University of Nottingham, said:

“It is impossible to know why this has been suggested now given there has been no change in the evidence.  The decision seems political given it is against the Scottish and other UK scientific advice that has been given.  There is no indication to make this UK wide due to the lack of evidence and strong possibility that they will not work.  They might provide a false sense of protection reducing the need for other known effective measures such as distancing in shops.  The guidance excludes people with asthma from wearing masks which is a large percentage of the population.  It is recommended that the mask is washed at 60 deg after each use.  This will destroy many modern fabrics and washing  a single item, or a few items, is very wasteful environmentally for no benefit.  They are suggesting people use cloth masks but no doubt hospital masks will be obtained by some people in the belief they are better or people cannot obtain cloth masks.  My only suitable item is a thermal neck warmer which would be impossible to use comfortably and shops are currently closed to purchase alternatives.”


Prof Ian Jones, Professor of Virology, University of Reading, said:

“The decision follows similar advice in several other European countries emerging from lockdown and is, simply, a no brainer. The arguments against mask use always centre on if they are worn appropriately, if they lead to a false sense of security or if their use will limit supplies. But the real scientific question is “can they reduce transmission” and the answer to that is yes. There will always be a level of misuse and usage when it is pointless to do so but that does not detract from them having a percentage impact overall. In essence it is no different from parents telling their children to “put your hand to your mouth” when they cough. The issue of supply is obviously important, priorities will need addressing and alternatives suggested, but the recommendation is reasonable advice that can help keep the epidemic at a basal level, especially as social mobility returns.”  


Dr Simon Clarke, Associate Professor in Cellular Microbiology, University of Reading, said:

“The announcement by the Scottish Government that it will now advise people to cover their faces in certain enclosed spaces is a significant one.  The First Minister has been clear that she follows the science in formulating policy during this crisis, so I will be interested to hear what new evidence has come to light or perhaps what they’ve now decided to discount.  Professor Jason Leitch, Scotland’s National Clinical Director has previously been very firm in stating that “masks in the general population don’t work”, so I’m keen to hear what’s changed.  I do hope that someone of his stature is giving advice based on evidence rather than political imperative.”


Declared interests

None declared


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