The secret weapon: face masks
They're all useful, if used correctly.
TL;DR: Medical face masks are less useful than N95 respirators, but not very much less so and better than nothing. Even just cloth is better than nothing, if used properly.
Info, references below but, first, my disclaimer: I’m not a doctor, this is not medical advice or advice of any other kind, I’m just referring to studies, use common sense, I shall not be held liable for the application or misapplication of any of the above. Full disclaimer here.
I looked at studies comparing medical masks and N95 respirators (references below). I only considered those on the field (i.e., no mechanical analysis or use of machines; only PPEs worn by doctors in hospitals) and those with pathogens of size comparable to COVID-19.
Of the 3 studies I found, 2 reported no significant difference in effectiveness and 1 reported that N95 was more effective. The last study is the only one reporting that participants were involved in high-risk procedures, whereas the others only reported use in proximity.
References:
https://jamanetwork.com/journals/jama/fullarticle/2749214… via @StephenPiment
https://jamanetwork.com/journals/jama/article-abstract/184819…
https://atsjournals.org/doi/full/10.1164/rccm.201207-1164oc… via @krystoferivanov
Also the studies mentioned in the tweet below are relevant:
Perhaps more importantly, the study below (via @naval) shows that even t-shirts and scarves are somewhat effective, though very much less so than medical masks.
Two more reasons to wear masks:
It seems to me that there are only 3 valid arguments not to wear masks today, and that's only under the current situation in which supply is limited.
Healthcare workers need them.
If personal supply is limited, you should use them only when the risk is higher.
Masks might induce self-harming behavior such as touching your nose, lips or eyes because you sweat, touching the exterior or their strings and then touching your nose, lips or eyes or giving a false sense of security and making you take risks you wouldn’t take otherwise, such as visiting your parents.
Wearing a medical mask, or even a scarf:
Is definitely not even close to being 100% effective.
Is better than nothing.
It's useful not only because it protects you, but especially because it protect other.
Shouldn't give a false sense of security.
Should be done knowing the risks and how to mitigate them (more on this below).
One additional reason why wearing a scarf is better than nothing if done properly, is that the more people wear something, the more *other* people are incentivized to wear something too, protecting the herd in a way which has less side effects than getting everyone sick.
I've read advice such as the below and I'm not in a position to say whether they are net positive or net negative, but I post it here for completeness (via @StephenPiment)
Some more information which might be relevant:
Also, and this is just my personal guess based on my limited knowledge, if you use scarves make sure to wash them at high temperature before reusing! (30 Celsius is definitely not enough; I've read 60 Celsius for at least 30 mins)
In general, PPEs aren't safe to reuse unless sanitized, and some cannot be sanitized without compromising their effectiveness (and thus cannot be reused).
Moreover, careful not to touch any part which might have been exposed to the virus while removing them or, if you do, wash your hands appropriately before touching anything else.
Also, make sure that you know how to safely dispose of them after use without them becoming an infection risk.
Finally, again, my disclaimer: I’m not a doctor, this is not medical advice or advice of any other kind, I’m just referring to studies, use common sense, I shall not be held liable for the application or misapplication of any of the above. Full disclaimer here.