April 30, 2020

expert comments about face coverings and COVID-19

Some further comments on face coverings and COVID-19 following comments made about face coverings and their potential role in the lifting of lockdown restrictions in this evening’s Government press conference.

Comment issued on Friday 1st May 

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

Is there robust scientific evidence suggesting a benefit of face masks in preventing virus transmission?

“No.  Even most advocates of face masks would admit that there is no strong scientific evidence whatsoever.  A lot of them basically just say: “it makes sense to use them”.

Is it more about giving people confidence to go about their daily lives when measures are lifted?

“There is no evidence for this.  This is one of the things that one would check in a proper scientific study.  There are no such studies and the truth may well be that people will have less confidence.

What do we know from scientific evidence about whether face masks are beneficial?

“Again, there are no robust scientific studies.  Some people suggest that masks must be beneficial as they stop the saliva droplets but they do not mention the potential side effects, or they just could not think of any.  A good scientist has to proactively challenge her/his own hypothesis.  In my letter I have listed the potential side effects.  It is not time to act without evidence.

“By robust scientific study I mean those involving people and measuring their risk to develop/transmit the disease.  All other kinds of studies made in labs (e.g. to see if masks block the droplets using lasers etc.; check how the virus behaves in certain conditions etc.) are not answering the relevant questions.  We need clinical and population studies on face masks.  Face masks may well help the coronavirus – but we don’t have strong evidence either way.

“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: https://www.bmj.com/content/369/bmj.m1435/rr-40.”

Comments issued on Thursday 30 April

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

“Face coverings provide modest protection to others when the person wearing the covering has the virus and no symptoms, or some symptoms but not enough to recognise that they need to stay at home.  Wearing a mask or a scarf on public transport, in a shop or in other indoor settings where it is difficult to stay 2m away from others will, I think, become part of the ‘new normal’ we all need to get used to until effective COVID-19 treatments or a vaccine is available.  Employers should consider making masks or coverings available in settings where social distancing is difficult as workplaces gradually start to open up again.

“In Scotland, we are already seeing more and more people taking this up, following Scottish government advice earlier this week.  I expect the rest of the UK to follow.  Small measures can add to bigger ones in public health.  For the time being, covering our nose and mouth in indoor public places where social distancing isn’t possible is the responsible thing to do until the pandemic is under control.  This seems strange to us in the UK, but it has been accepted in a number of other countries for some time.”

Prof Robert Dingwall, Professor of Sociology, Nottingham Trent University, said:

“I certainly don’t think that face coverings will give people confidence that they can go back to work.  They will be a constant reminder that interaction with other people is dangerous, that going out into society is risky, and that human contact is to be avoided.  I find it very odd that a Prime Minister who has been so critical of the voluntary covering of women’s faces by the niqab should be such an enthusiast for encouraging or even compelling many people to do so for reasons that do not have a robust scientific basis.  This is not ‘following the science’ in any sense that it would be commonly understood, even if we think that that claim is more problematic than ministers allow.  Face coverings are more likely to amplify fear than promote confidence.”

Prof Robert West, Department of Behavioural Science and Health at UCL, and Prof Susan Michie, Director of the UCL Centre for Behaviour Change, UCL, and Fellow of the Academy of Medical Sciences, said:

“We are just completing a rapid review on face masks led by Olga Perski that we think brings together the relevant evidence on face masks in community settings (not health and social care settings) and uses a Bayesian approach to assess directly the relatively likelihood that they confer benefit or harm.  The conclusion is that randomised controlled trial evidence is almost completely equivocal on the issue of benefit versus harm on laboratory or clinically confirmed respiratory infections.  We therefore have to rely on judgements.

“Some health experts are using the ‘it stands to reason’ argument that face masks will confer a benefit but in community settings there are genuine risks that have to be considered.  One of these is false reassurance which may lead people to fail to adhere to other personal protective behaviours (i.e. physical distancing, using tissues to catch coughs and sneezes, hand-cleansing, disinfecting surfaces and objects, not touching eyes, nose or mouth).  Johnson’s remarks about face masks “giving people confidence they can go back to work” goes against sensible scientific advice and are unhelpful in potentially fostering precisely the false reassurance we need to avoid.”

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

“The Prime Minister’s hint that the government may be about to recommend face coverings as the country begins to come out of lockdown comes not a moment too soon.  The Office for Budget Responsibility has estimated that lockdown reduces our national economic output by almost one-third.  Many people who are staying at home simply cannot work – and thousands have already lost their jobs either temporarily or permanently.  It is imperative that we use all possible measures to help get society up and running again – back to work, back to contributing to their communities and back to visiting and supporting their older relatives.  One such measure is covering our faces when we are in crowded places such as supermarkets, public transport and mass gatherings.  Between 30 and 80 percent of people who pass on the Sars-CoV-2 virus do so before they become symptomatic [1,2].  A double layer of cotton in front of the mouth and nose reduces droplet emission by more than 80 percent (95 percent if a waterproof lining is used) [3].  So a home-made face covering will greatly reduce the risk each of us poses to our fellow citizens – and will also give some protection to the wearer.  Importantly, a culture of wearing face coverings in public will convey some important societal messages: we’re taking collective responsibility for stamping out this pandemic (my mask protects you; yours protects me).  This is an unprecedented measure, but we live in unprecedented times.  It will be better than staying in lockdown forever.”

1. Kay J. COVID-19 superspreader events in 28 countries: critical patterns and lessons. Quillette 2020;23rd April

2. Gandhi M, Yokoe DS, Havlir DV. Asymptomatic Transmission, the Achilles’ Heel of Current Strategies to Control Covid-19: Mass Medical Soc, 2020.

3. Konda A, Prakash A, Moss GA, et al. Aerosol Filtration Efficiency of Common Fabrics Used in Respiratory Cloth Masks. ACS Nano 2020 doi: 10.1021/acsnano.0c03252

All our previous output on this subject can be seen at this weblink:

www.sciencemediacentre.org/tag/covid-19

Declared interests

None received.