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Whether you're pro- or anti- masks (I'm neither), it is important we assess any downsides & investigate ways these could be mitigated. We recently reviewed 37 studies on this which I'll summarise; preprint here -> https://www.medrxiv.org/content/10.1101/2020.06.16.20133207v1
1. Adherence to face mask - in 8 trials that measured it was modest (average 47% more wearing in face mask group); but appeared similar in combined face mask + handwashing group (so no "risk compensation" - for which we found no other studies). Adherence decreased with time.
2. Adherence was worse for N95 than surgical masks. This illustrates need to consider & measure discomforts (which is one possible explanation for why N95s appear no better than surgical masks in 4 RCTs of preventing flu, eg Radonovich 2019 ).
3. Commonest complaints were the discomfort, especially restricted breathing & facial. Communication was also a common problem - and a reason to discontinue use (mitigations might be face shield or transparent masks). Note special problem for lip readers.
4. Mitigation could be gained thru (1) limiting situations or duration of mask wearing or (2) alternatives such as transparent masks or face shields. Education appeared to have little impact.
5. No head-to-head studies exist of masks versus face shields. Such trials seem urgent & important but, as well as prevention of viral transmission, should measure adherence and downsides. https://www.ijidonline.com/article/S1201-9712(20)30399-4/fulltext
