The author has shown that wearing face masks by the public outside of hospital/nursing settings is useless as source control for COVID-19. When mandated, it becomes harmful .
Other research has shown that wearing masks by the public in general settings is not effective against the spread of a respiratory epidemic : “During the 2009 pandemic of H1N1 influenza (swine flu), encouraging the public to wash their hands reduced the incidence of infection significantly whereas wearing facemasks did not”
A 2017 systematic review and meta-analysis found similarly even for surgical masks : “Facemask use provided a non-significant protective effect.”
Howard et al. (preprint, ver. 3)  is a full throated advocacy for universal masking. It cherry-picks references.  (Howard #10) was a study of household context in China. It found that wearing masks at home before onset of COVID-19 symptoms in a typical three generation Chinese household sharply decreased COVID-19 transmission. Nevertheless, this is not relevant for public settings.
Howard et al. does not always accurately represent findings in the references it cites.
 (Howard #26) was a good RCT conducted in multiple university residence buildings. It was correctly quoted as finding “a significant association between the combined use of face masks and hand hygiene and a substantially reduced incidence of ILI during a seasonal influenza outbreak.” Omitted was a (less significant) association between the use of face masks alone and increased incidence of ILI.
 (Howard #15) was a 2011 meta-review. It found that wearing surgical masks was effective, mostly in hospitals and in use by health care workers. It did not address wearing cloth masks. The following shows the difference.
 (Howard #27) was a study in Vietnam, which compared cloth masks, surgical masks, and no masks in healthcare workers. The result: infection rate was 3.5 times higher among healthcare workers wearing cloth masks compared with no masks. The surgical masks did have desired effect, decreasing infection rate 3.8 times compared with no masks.
 (Howard #16) is a 2020 meta-review pre-print with the same lead author as . It found that “There was insufficient evidence to provide a recommendation on the use of facial barriers without other measures”, “Nine trials compared masks with no masks. … Pooling of all nine trials did not show a statistically significant reduction of ILI cases.” Two among of the nine trials were conducted on healthcare workers. Most of the trials were conducted with surgical masks or respirators.
Finally, Stutt et al.  assumed that wearing masks is effective in decreasing spread of the coronavirus for modeling purposes. This assumption was baseless.
Cloth face masks for personal protection might be more effective than for source control for two reasons:
- On inhalation through the mouth, the fabric sticks to the mouth, so more of the airflow goes through the fabric. It is other way around on exhalation.
- People take better care of the masks and masking when they wear them to protect themselves.
A side note:
Could breathing through the nose be effective to slow down the Wuhan coronavirus spread?
 Goldstein L. Does Universal Mask Wearing Decrease or Increase the Spread of COVID-19? Watts Up With That? 2020. https://wattsupwiththat.com/2020/07/25/does-universal-mask-wearing-decrease-or-increase-the-spread-of-covid-19/ (accessed August 11, 2020).
 Isaacs D, Britton P, Howard‐Jones A, Kesson A, Khatami A, Marais B, et al. Do facemasks protect against COVID‐19? J Paediatr Child Health 2020;56:976–7. https://doi.org/10.1111/jpc.14936.
 Saunders-Hastings P, Crispo JAG, Sikora L, Krewski D. Effectiveness of personal protective measures in reducing pandemic influenza transmission: A systematic review and meta-analysis. Epidemics 2017;20:1–20. https://doi.org/10.1016/j.epidem.2017.04.003.
 Howard J, Huang A, Li Z, Tufekci Z, Zdimal V, Westhuizen H-M van der, et al. Face Masks Against COVID-19: An Evidence Review 2020. https://doi.org/10.20944/preprints202004.0203.v3.
 Wang X, Ferro EG, Zhou G, Hashimoto D, Bhatt DL. Association Between Universal Masking in a Health Care System and SARS-CoV-2 Positivity Among Health Care Workers. JAMA 2020. https://doi.org/10.1001/jama.2020.12897.
 Aiello AE, Perez V, Coulborn RM, Davis BM, Uddin M, Monto AS. Facemasks, Hand Hygiene, and Influenza among Young Adults: A Randomized Intervention Trial. PLOS ONE 2012;7:e29744. https://doi.org/10.1371/journal.pone.0029744.
 Jefferson T, Del Mar CB, Dooley L, Ferroni E, Al-Ansary LA, Bawazeer GA, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Cochrane Database of Systematic Reviews 2011. https://doi.org/10.1002/14651858.CD006207.pub4.
 MacIntyre CR, Seale H, Dung TC, Hien NT, Nga PT, Chughtai AA, et al. A cluster randomised trial of cloth masks compared with medical masks in healthcare workers. BMJ Open 2015;5:e006577. https://doi.org/10.1136/bmjopen-2014-006577.
 Jefferson T, Jones M, Al Ansari LA, Bawazeer G, Beller E, Clark J, et al. Physical interventions to interrupt or reduce the spread of respiratory viruses. Part 1 – Face masks, eye protection and person distancing: systematic review and meta-analysis. MedRxiv 2020:2020.03.30.20047217. https://doi.org/10.1101/2020.03.30.20047217.
 Stutt ROJH, Retkute R, Bradley M, Gilligan CA, Colvin J. A modelling framework to assess the likely effectiveness of facemasks in combination with ‘lock-down’ in managing the COVID-19 pandemic. Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 2020;476:20200376. https://ift.tt/37iftDW.
via Science Defies Politics
August 11, 2020 at 07:09PM