Face masks for the public during the covid-19 crisis
BMJ 2020; 369 doi: https://doi.org/10.1136/bmj.m1435 (Published 09 April 2020) Cite this as: BMJ 2020;369:m1435Read our latest coverage of the coronavirus pandemic
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Dear Editor,
I agree with the well argued article and editorial.
I would like to add a further argument in favour of public wearing facemasks - that of viral dose influencing disease severity.
If initial viral dose is a factor in subsequent disease severity, masks could have a huge impact on outcomes. Viral dose has been proven to be factor for other viruses in animal studies and human challenge studies. We do not have, and clearly cannot expect to have direct evidence of this for COVID19 but it is not unreasonable to assume viral dose could play some role.
Without evidence to the contrary, I would prefer that the infected person walking nearby me in the supermarket delivers me a smaller dose of virus due to some being retained by a cloth mask, in the reasonable hope that even I still become infected the subsequent disease is less severe.
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Dear Editor,
Many people are already wearing face masks, especially the green clinical ones. There are already concerns about PPE shortages in clinical settings. The crisis of plastic pollution has not gone away. Most masks will go to landfill and I am seeing many blowing in the wind, which is a major infection risk if the wearer has the infection.
The CDC are advising cloth masks made from old cotton t-shirts. These might not be perfect but they keep clinical masks in clinical settings. They are more environmentally friendly because they are recycling materials, can be washed and reused, and are more biodegradable when disposed. They can be made locally, and act as a reminder that we all have a responsibility to minimise our risk of onward transmission.
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Dear Editor See WSJ April 9, 2020 A18: Hong Kong Sees Masks As Key to Protection, By John Lyons
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Dear Editor
"The ounce of evidence is better than tons of literature"
As in the article itself, there are ounces of evidence in tons of literature which indicate the benefits of social /universal masking in the near past in managing influenza. Influenza is not even understood fully to date but still indicates benefits. The term precautionary principle itself was devised in Germany in the dilemma at that time but later on it was proved beneficial.
Just on the analogy of scientific advancement, the Covid 19 virus and its tackling stretegies are evolving on a day to day basis; if one waits for ample evidence in this scenario now, we might get many, by sacrificing many, human lives.
Therefore, health policy makers have to adopt the precautionary principle on the basis of ethics with available evidence. The principles of medical ethics like beneficence, non-maleficence, justice and autonomy would be weighed down while taking such decision making. If an ounce of evidence of non-maleficence (no harm) for universal masking with cloth is strong, then one should advocate for this practice. It indirectly strengthens the principle of beneficence and justice to frontline health professionals in dire need of medicated masks. The principle of autonomy could be achieved by informing the benefits of community masking (as per CDC) to communities and encourage them to take an informed decision.
Some countries like Japan, Singapore and lately India are advocating for universal masking, in the first instance generating the hypothetical evidence of slow transmission.
"When uncertainty prevails, the certain thing to do is do some uncertain things in an ethical way"
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Dear Editor
My problem with masks is not that they have not been proven effective, it is that they have not been proven safe. Given the rationale for their use they would become contaminated with virus while being worn and as such become more contagious than no mask. Plus touching to reposition them contaminates hands, gloved or not. Also coughing or sneezing thru them would propel virus into the immediate area. This blind dictate for their use is primitive unvalidated potentially dangerous reasoning.
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Dear Editor:
The precautionary principle not only applies to strategies for approaching issues of potential harm but also to those which protect our body from that harm. As we can deduce from Professor Trisha Greenhalgh and colleagues' paper, there are many confounding variables and facts that influence the reviewers' appreciation in favor of using face masks for preventing CoViD19. Why only think about face mask use, and not on optimum physiological state of the people who wear those protective face masks, knowing previously that the pore size of an excellent face mask does not exceed 2.5 micrometers in diameter and that if the radius of a spherical coronavirus ranges from 50 to 80 nanometers; this indicates that the face mask material can easily allow the passage of between 10 and 25 viral particles per pore.
On several occasions, using the great daily opportunity offered by the BMJ editorial group, we have insisted that it is urgent to look at the other side of the coin of the devastating problem that is the CoViD pandemic generating around the world. It has to do with the dynamics of the normal functioning of the human organism.
Inspired atmospheric air is a toxic mixture of gases: it always contains microorganisms, hundreds of compounds, and particulate matter, for instance, supramolecular complexes such as viruses, formed of nucleic acids, lipid and proteins. All of them always have been considered very dangerous to human health, because they may significantly contribute to development of several diseases, mainly in those organic systems in direct contact with the environment. This means the skin and respiratory, gastro-intestinal, and genitourinary systems. SARS Coronary viruses can cause severe harm to humans because of a deleterious immunologic function related to permanent protein malnutrition; the harm is characterized by deficient activity in the innate and adaptive immune responses that produce delayed airway epithelial responses to permanent antigen inhalations, thus allowing microbial colonization and invasion.
Working well, and without masks, the nasal cavity mucosa acts as a wonderful filter and traps pollutants and other harmful substances found in the air. In addition to that, it contains very active compounds - for instance, the dipeptidil peptidase more popularly known as angiotensin converting enzyme and the neutral endopeptidase enzymes - which in normal physiologic conditions, neutralize the action of pro-inflammatory compounds. There are also substances with a high scavenger activity, antioxidants which protect very well airway epithelial cells. The absence of well functioning immune airway epithelia creates the ideal ground for entering and proliferation of microorganisms which potentiate responses related to bronchoconstriction, recruitment, and activation of neurogenic inflammation.
Throughout world history, several objects have been used to improve the social presentation of people. Dresses, jeans, hats, necklaces, bracelets, glasses, several kind of jewelry objects, at different times have been fashionable among people. Because of the great variety of face masks distributed and sold now, there are of all kinds and colors, with impressions alluding to anything but health. The way masks are used by people in their daily life means, we believe, that a face mask is a fashion icon in CoViD19 times.
Competing interests: No competing interests
Preventing the spread of the coronarovirus causing Covid-19 is currently based in most countries on social distancing for all. Following Geoffrey Rose, this preventive strategy is "population-based" (1,2). Strengths of this approach, if respected, are its radicality to prevent spread of the virus and the large potential benefit at a population level. Further, because it is legally enforced, it does not rely on the good will and motivation of the people (1,3). One major limitation is however the huge harm on economic activities, making impossible its long-term implementation.
With the decrease in the number of cases, public health authorities will move progressively toward a "high-risk" preventive strategy (1), i.e., through the finding and isolation of cases and contacts, also called a "catch-and-isolate" approach (3). In the absence of vaccine, and as long as herd immunity is not high enough, this is an efficient strategy to prevent new epidemic waves. However, it requires important material and human ressources. Further, while it may have worked in countries like Singapore, it will be much more difficult to be implemented on a large scale in European countries.
Face masks for all can be considered as an in-between preventive strategy (4). It has to be seriously considered because it will help lower the degree of social distancing and ease the - urgently needed - return toward a higher level of economic activity. After a period of acclimatation, its acceptance will be certainly high even in populations not used to wearing face masks.
1. Rose G. Strategy of Preventive Medicine. Oxford, UK : Oxford University Press , 1992. Re-edited in 2008.
2. Chiolero A, Paradis G, Paccaud F. The pseudo-high-risk prevention strategy. Int J Epidemiol. 2015;44(5):1469–1473.
3. Watkins J. Preventing a covid-19 pandemic. BMJ. 2020; 368:m810.
4. Greenhalgh T et al. Face masks for the public during the covid-19 crisis. BMJ 2020; 369:m1435
Competing interests: No competing interests
Dear Editor
The article by Trisha Greenhalgh and colleagues presents a pragmatic argument for face mask use by the public in response to COVID-19. [1] Their precautionary principle approach in the absence of clear evidence of benefit includes invoking the parachute approach to evidence-based medicine. [2] This seems sensible and to extend that analogy, while a trial of parachutes seems redundant, one would remain concerned about matters such as quality control, ‘user’ training and ultimately, reach. How guidance such as that offered by the CDC may be implemented at scale and how it may work to benefit some but not others needs consideration. [3]
The health impact of COVID-19 and living within social distancing restrictions will be experienced differently within the populations affected. For example, manual key workers, those unable to work from home or those who fear the loss of their jobs will have increased exposure. Social distancing works better for some than others. [4] Levels of risk factors such as smoking will sharply differ across social gradients. [5] Whilst the pandemic will affect all communities, some will be more affected than others.
In general, engagement with supportive health care and health promotion messages will also vary along socio-demographic lines and levels of health literacy. [6] Currently promoted health behaviours to address COVID-19 such as hand washing will mirror such generic differences. In a cross-sectional survey in Hong Kong fifteen years after the SARS outbreak, higher education level and lower age predicted hand hygiene behaviour. [7] Also in Hong Kong, Suen and colleagues found female gender and higher-level education better predicted hand hygiene knowledge and behaviour. [8] Individuals and communities will respond more and less effectively when presented with health promoting guidance.
While tackling COVID-19 requires rapid action from governments, there is also a possibility that key messages will unintentionally cause some differences in response which re-enforce health inequality. A policy move towards promoting face masks for the public seems desirable in the absence of clear harms. Nevertheless, care should be exercised to ensure that variable uptake does not re-enforce existing health inequalities and so perpetuate the effects of Tudor Hart’s Inverse Care Law. [9]
References
1. Greenhalgh T, Schmid MB, Czypionka T, et al. Face masks for the public during the covid-19 crisis BMJ 2020;369:m1435.
2. Potts M, Prata N, Walsh J, Grossman A. Parachute approach to evidence based medicine. BMJ 2006;333:701-3. 10.1136/bmj.333.7570.70110.1136/bmj.333.7570.701 17008675
3. Centers for Disease Control. How to protect yourself. 4 Apr 2020. https://www.cdc.gov/ coronavirus/2019-ncov/prevent-getting-sick/prevention.html?CDC_AA_refVal=https%3A% 2F%2Fwww.cdc.gov%2Fcoronavirus%2F2019-ncov%2Fprepare%2Fprevention.html.
4. https://www.theguardian.com/commentisfree/2020/apr/01/coronavirus-covid-...
5. Office for National Statistics. Adult smoking habits in the UK: 2018. Statistics Bulletin Release date 2 July 2019
6. Marmot M, Allen J, Boyce T, Goldblatt P, Morrison J. (2020) Health equity in England: The Marmot Review 10 years on. London: Institute of Health Equity
7. Wong JSW, Lee JKF. The Common Missed Handwashing Instances and Areas after 15 Years of Hand-Hygiene Education. Journal of Environmental and Public Health Volume 2019, Article ID 5928924, 7 pages https://doi.org/10.1155/2019/5928924
8. Suen LKP So ZYY, Yeung SKW, Lo KYK, Lam SC. Epidemiological investigation on hand hygiene knowledge and behaviour: a cross-sectional study on gender disparity BMC Public Health (2019) 19:401 https://doi.org/10.1186/s12889-019-6705-5
9. Tudor Hart J. The Inverse Care Law. The Lancet 1971; 297, 405-412
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Dear Editor
Another useful review, however this weekend it is cold comfort as we all learn rapidly how to manage the resources available to our local health and social care systems. Pressure has to bear on government to commission the production of PPE that is of a standard that works (specification unclear); antigen and antibody tests that are reliable (antigen test has ~70% sensitivity); a vaccine that will achieve sufficient herd immunity (next year).
What is being forgotten here is that care staff in particular are in the front line but have had little training in how to protect themselves and their clients. You could provide an endless supply of FP3 masks but if you don't give training in donning and doffing they could do little more than be a reminder not to touch your face.
Competing interests: No competing interests
Re: Face masks for the public during the covid-19 crisis
Dear Editor,
we happened to make a mistake with regard to reference 39. In our article we cited a republication instead of the original publication. The correct reference 39 should read:
Smith GC, Pell JP. Parachute use to prevent death and major trauma related to gravitational challenge: systematic review of randomised controlled trials. Br Med J 2003;327:1459-61.14684649
We apologize for this error.
Manuel Schmid
Competing interests: No competing interests