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A cluster randomised trial of cloth masks compared with medical masks in healthcare workers
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  • Published on:
    It is important to consider the size and incident flow rate of particles tested here compare with the size and typical incident flow rate of respiratory droplets?
    • Daniel W Sazer, Graduate student researcher Rice University Department of Bioengineering

    Very nice work by the authors. Perhaps they could provide additional details about the methods used here to test particle filtration.

    Conflict of Interest:
    None declared.
  • Published on:
    A cluster randomised trial of cloth masks compared with medical masks in healthcare workers

    The suggestion that cloth masks can lead to increased infection compared to no mask is not substantiated The control arm had less than 1% of no mask use and therefore the statement is an assumption not a proof . It could be possible for bacteria or fungi that could multiply on the mask but for virus it would have to shown there is more bioavailability than no mask .

    Conflict of Interest:
    None declared.
  • Published on:
    Vicki Macleod

    The authors do not state what kind / standard of cloth masks were used. Is there any chance they could do this. Given the huge shortage of FFP2 and FFP3 masks, it would be helpful to know the authors’ views of advice from the CDC in the US. https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/diy-cloth...

    Conflict of Interest:
    None declared.
  • Published on:
    Microbiologist & Regional Industrial Hygienist
    • Jorge K. Leong, Biological scientist U.S. Occupational Health & Safety Administration (former employer)

    I like the article. However, in my humble opinion, I wish there is a Material section in it describing the different types of fabrics the masks are made of. If circumstances do not permit detail descriptions of individual masks, it would generate more scientific value if the materials can be grouped and categorized, at least broadly, such as solid cotton sheet, gauze, etc. Similarly, statements, on the number of fabric layers in and photographs of the different shapes of representative groups of masks would be very useful.

    Conflict of Interest:
    None declared.
  • Published on:
    Cloth masks for general population

    Thank you for your work. It seems that in addition to healthcare workers, many people in the general population are referring to your research about cloth masks for guidance about homemade ("DIY")masks for use in the general population. If you are able to provide an addendum to your original research similar to this one addressing the question of their suitability for the general population that would be very helpful.

    Conflict of Interest:
    None declared.
  • Published on:
    Why not interpret the cloth masks as being less protective rather than presenting high risk?

    This is a critical study, being the only C-RCT to evaluate cloth masks, and it will carry inordinate weight until more studies are done. It makes findings and recommendations which have pretty drastic implications and gainsay widespread practice. It therefore is appropriate, I think to test it with some devil's advocate interrogation. I wish to raise 3 such arguments that I hope will generate debate.

    1. The 2015 study shows that the cloth masks have higher rates of infection in the health workers (RR 1.51 for CRI, 1.72 for for lab confirmed infection). Actual infection rates were 7.6% versus 4.8%. But as the authors have stated, there was no no-mask control group. To quote the authors "The finding of a much higher rate of infection in the cloth mask arm could be interpreted as harm caused by cloth masks, efficacy of medical masks, or most likely a combination of both.” But why not draw the conclusion that the cloth masks are simply less effective at reducing infection.

    For example, some studies indicate medical masks are highly effective – assume an 80% reduction of infection, for both N95 and surgical masks. If, say, out of 100 infections that would have occurred, medical masks prevented 80, resulting in 20 infections, and according to this study, cloth masks would result in 51% more (RR=1.51), i.e. 30 cases, or at upper limit of 95%CI, RR=2.49 i.e. 50 cases, then the cloth masks have still avoided between 50 and 70 cases, i.e. more than half...

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    Conflict of Interest:
    None declared.
  • Published on:
    COVID-19, shortages of masks and the use of cloth masks as a last resort
    • Chandini R MacIntyre, Academic physician The Kirby Institute, University of New South Wales
    • Other Contributors:
      • Chi Dung Tham, Academic physician
      • Holly Seale, Academic
      • Abrar Chughtai, Academic physician

    Critical shortages of personal protective equipment (PPE) have resulted in the US Centers for Disease Control downgrading their recommendations for health workers treating COVID-19 patients from respirators to surgical masks and finally to home-made cloth masks. As authors of the only published randomised controlled clinical trial of cloth masks, we have been getting daily emails about this from health workers concerned about using cloth masks. The study found that cloth mask wearers had higher rates of infection than even the standard practice control group of health workers, and the filtration provided by cloth masks was poor compared to surgical masks. At the time of the study, there had been very little work done in this space, and so little thought into how to improve the protective value of the cloth masks. Until now, most guidelines on PPE did not even mention cloth masks, despite many health workers in Asia using them.

    Health workers are asking us if they should wear no mask at all if cloth masks are the only option. Our research does not condone health workers working unprotected. We recommend that health workers should not work during the COVID-19 pandemic without respiratory protection as a matter of work health and safety. In addition, if health workers get infected, high rates of staff absenteeism from illness may also affect health system capacity to respond. Some health workers may still choose to work in inadequate PPE. In this case, the physic...

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    Conflict of Interest:
    We were the authors of the 2015 RCT , which was funded by an Australian Research Council Linkage Grant with 3M as the partner on the grant.