Covid-19: What is the evidence for cloth masks?

The current pyramid of evidence puts the randomized trial at the top. But the question of whether facemasks work is a question about whether they work in the real world, worn by real people, in real situations.

This is a pragmatic trials question. We should therefore be focusing the argument of benefit or harm around evidence generated from pragmatic trials – trials which have evaluated masks in real world settings. The recent rapid systematic review looked at the question of what is the evidence facemasks work compared to no facemasks (and included evidence from pragmatic and more explanatory type trials; and did not consider the evidence from pragmatic trials of evidence of different types of facemask). The question we should consider to determine whether facemasks will be of benefit in the current pandemic is: what pragmatic evidence is there that facemasks work when worn by real people in real setting in real situations. Here is my summary of the evidence on this:

Evidence from controlled settings

There is little doubt that masks works in controlled settings – they stop particulates penetrating the air [Leung 2020]. Facemasks also seem to prevent infection spreading when worn by people who are infected [Brainard 2020]. Yet, this doesn’t tell us if they will work in the real world.

Evidence from trials of facemasks vs no mask

Systematic review of facemasks vs no mask [Brainard 2020]

There are three RCTs identified in this review where people wore masks to try to prevent other people becoming infected (primary prevention). The authors of the review interpret the evidence from these three RCTs as a small non-significant effect on influenza like illness. But, this is an incorrect interpretation of the result (RR=0.95, 95% CI: 0.75 to 1.19) as this result is compatible with both benefit and harm. The evidence from these three trials should therefore be interpreted as uninformative (or consistent with either benefit or harm). There are observational studies in this review, but these do not allow us to answer the question of whether the masks provide protection as they will be subject to confounding. The largest of the three RCTs was a pragmatic cluster trial in pilgrims [Alfelali 2020]. This is a well conducted pragmatic cluster randomized trial with low risk of bias, but suffered from low compliance. This found OR 1.35, 95% CI 0.88-2.07 which although non-significant, is more suggestive of harm than benefit.

Conclusion: The largest and most pragmatic trial (which informs on how facemasks will perform in the real world) assessing the benefit of facemasks vs no mask is suggestive of more harm than benefit.

Evidence from trials comparing different sorts of facemasks
(This is not based on a systematic review, so there may be other evidence that I am unaware of)

1. CRT of N95 vs surgical mask in health care workers (Respect Trial) [Radonovich 2019]. Large pragmatic trial in health care works. Low risk of bias. The trial reported a non-significant finding which it interpreted as “no significant difference”. However, despite being non-significant, the confidence interval for the primary outcome rules out anything but a small possibility of any clinically important benefit of the N95 respirator. Again, authors have mis interpreted the statistical finding (OR 1.18 95% CI: 0.95 to 1.45). The evidence from this trial in fact supports more that the N95 respirator might be associated with a small amount of harm. Compliance was high. Therefore, this “surprising finding” of increase risk of the N95 mask (when it is known to perform much better in controlled settings) might be attributable to risk compensation.

2. CRT of surgical vs cloth masks in health care workers in LMIC. [MacLntyre 2015] well conducted low risk of bias. Overwhelmingly suggests harm as opposed to benefit (RR=13.00, 95% CI 1.69 to 100.07). The authors conclude this increased risk is likely to be due to the penetration of cloth marks with disease particulates.

Conclusion: The evidence from pragmatic trials (people wearing masks in everyday settings) suggests wearing of facemasks both induces risk compensation behavior and increased virus spreading from poor mask quality.

References

[Leung 2020] Leung, N.H.L., Chu, D.K.W., Shiu, E.Y.C. et al. Respiratory virus shedding in exhaled breath and efficacy of face masks. Nat Med (2020). https://doi.org/10.1038/s41591-020-0843-2

[Brainard 2020] Brainard JS, Jones N, et al. Facemasks and similar barriers to prevent respiratory illness such as COVID-19: a rapid systematic review. medRxiv 2020.04.01.20049528; doi:10.1101/2020.04.01.20049528. https://www.medrxiv.org/content/10.1101/2020.04.01.20049528v1.full.pdf

[Radonovich 2019] Radonovich LJ Jr, Simberkoff MS, Bessesen MT, Brown AC, Cummings DAT, Gaydos CA, Los JG, Krosche AE, Gibert CL, Gorse GJ, Nyquist AC, Reich NG, Rodriguez-Barradas MC, Price CS, Perl TM; ResPECT investigators. N95 Respirators vs Medical Masks for Preventing Influenza Among Health Care Personnel: A Randomized Clinical Trial. JAMA. 2019 Sep 3;322(9):824-833.

[Alfelali 2020] Alfelali, Mohammad and Haworth, Elizabeth Ann and Barasheed, Osamah and Badahdah, Al-Mamoon and Bokhary, Hamid and Tashani, Mohamed and Azeem, Mohammad Irfan and Kok, Jen and Taylor, Janette and Barnes, Elizabeth Helen and El Bashir, Haitham and Khandaker, Gulam and Holmes, Edward Charles and Dwyer, Dominic Edmund and Heron, Leon and Wilson, Godwin Justus and Booy, Robert and Rashid, Harunor, Facemask versus No Facemask in Preventing Viral Respiratory Infections During Hajj: A Cluster Randomised Open Label Trial (March 8, 2019). Available at SSRN: https://ssrn.com/abstract=3349234 or http://dx.doi.org/10.2139/ssrn.3349234

[Maclntyre 2015] MacIntyre CR, Seale H, Dung TC, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open2015;5:e006577. doi:10.1136/bmjopen-2014-006577. pmid:25903751

Dear Editor

Ongoing confusion and debate about whether or not the public should wear face masks against covid-19 is causing more concern than building public confidence. The face mask is a common sense way of personal protection and it is not a new medicine or surgery that requires a hard scientific evidence before use. Any sensible person will know whenever there is a risk of infection, use appropriate gloves, mask, gown, disinfectants and isolate. But for the general public a simple face mask should be used now.

Of course there is no corona virus specific tailor made masks available now and that is not a scientific ground to condemn any other creative masks as no good or a possibly harmful means of spreading the disease. If that is the case, then our own cloths, coat, jacket, hand bags, accessories, etc. could be even more harmful in spreading the disease even faster than a tiny mask can do. This is a critical time, and a virus can enter the body easily through the breathing passages and any sensible attempt at personal protection, at least some resistance and filtration through a face mask, is better than no attempt at all; this is not a false sense of security. World advisory authorities have encouraged people to cough or sneeze in their own folded arm cloth with elbow bent. Is there any scientific evidence to prove that method is safe and protective and not itself a serious source of infection to spread the disease and make it even worse? A face mask in comparison is no more harmful than all these sources where we are at risk.

Science should provide evidence to justify that a face mask does not work before it can advise against it. The advisory authorities are more anxious about a sudden surge in huge demand for resources and political pressure on responsible bodies to supply masks to the entire population, but that is not at all necessary: people can use common sense to make their own face masks, as they are doing it in many parts of the world, rather successfully, and without any evidence of spreading the disease. Let’s not confuse people who are already confused being locked up at home, and let them make their own face masks without adding pressure on the reserved resources for health care staff and worrying advisory authorities, until science can give us better advice.

Dear Editor
I fully support the view common sense should come into the discussion of whether masks are useful.
1. Evidence that it works? There has never been any randomised trial done in an urban setting with exposure during a severe epidemic with the subjects exposed to elevators and public transport, and busy shopping areas. The lack of such trials means simply we do not know. But that does not mean mask use is of no use. It is simply that we are in a knowledge vacuum state. There is no evidence that it does not work either. We need proper trials , not pontification. WHO is taking a stand against a the use of mask on economic grounds rather that medical ground.
2. There are growing evidence that sars-CoV2 virus is viable for some hours in aerosol form, and it is generated in speech, and travel a fair distance with coughing. Mask wearing by everyone with likely reduce the release of such virus as well as giving protection to others. The percentage of asymptomatic covid-19 positive subjects is very high so if Europeans and Americans who have a cultural prejudice against mask all wear one, it will mean less transmission of the virus by asymptomatic positive subjects in their regions.
3. Social distancing is not always possible in urban environment. How do you do social distance with public transport, and elevator use, or with shopping. when not in a lockdown?
4. Mask is just one of the tools for reducing the public risk of getting infected. You need mask, social distancing, and diligent hand washing to be effective. I notice that many commentators forget to mention hand washing as a sine qua non when railing against the use of mask! People in Hong Kong , Taiwan, Korea do all three, and the result is there to see. If wearing a mask will make people forget social distancing , does social distancing reduce one's hand washing and that is the cause why the outbreak is so bad in Europe and America? Surely we should push for all three, rather than pontifying against the use of mask.

Dear Editor

Face masks as a protective measure against the spread of respiratory viruses have been in vogue among health care personnel. Their use has been advocated for protection against any infectious disease such as seasonal influenza, tuberculosis, other upper respiratory tract infections. The traditional advice given to patients also emphasizes the use of face masks or as such any other materials such as a piece of cloth or handkerchief to place over the mouth during cough or sneeze so that the infected droplets do not reach the health care provider during consultations and also the close contacts of the patient either in the home or in the workplace setting. Besides, they are also taught about hand hygiene involving hand washing with soap water or sanitizer along with maintaining social distancing measures. Such a practice is not new. However, the current pandemic has led to the controversies of using a face mask by affected persons, common people and health care staff.

The recommendations of the World Health Organization seem to be related to the availability of surgical face masks, which are in short supply throughout the globe and, hence, their rational use is limited to health care providers. The emerging problem with the SARS CoV 2 virus is that there are a large number of asymptomatic persons who are difficult to identify and they are the potential source of spreading the infection. With the limited knowledge about the transmission through droplet infections, speculation about transmission through routine breathing and aerosol besides fomites, contaminated surfaces (1), and quick transmission of the virus from one person to another, it seems to be imperative to consider that everyone is at risk when the virus has spread globally and taken large tolls.

Such an alarming figure of infection at a short time creates panic and every citizen needs protection. Under such circumstances, despite lack of evidence, the rationale of creating a barrier from getting droplet infection using any barrier means such as a mask prepared by using any cloth available in the household with the specification that the fabric of the cloth should not be seen (light should not pass easily through the fibres while placing it before a bright light source) could be useful to some extent, though not in totality in reducing the quantum of virus getting transmitted through droplets. (2) There is, thus, a need for educating the people about the use of such masks, their disposal, in addition to the need for hand hygiene and social distancing during this pandemic. We cannot wait for any randomized trials during this pandemic, rather, it should be considered as an opportunity to see the effectiveness of homemade masks.

References
1. Doremalen NV, Bushmaker T, Morris DH, Holbrook MG, Gamble A, Williamson BN, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Eng J Med March 17, 2020 DOI: 10.1056/NEJMc20049732020
2. Parker-Pope T. What’s is the best material for a mask ? The New York Times. Available at https://nyti.ms/2wgpCTB (published on 12th April 2020).