Face masks don't even have to work especially well to be effective:
Advice on whether or not to use face masks to limit the spread of the pandemic has varied from country to country, even differing by location within countries. These policies have had to balance whether there were sufficient supplies for medical personnel to divert some to the general public. And the whole issue was decided without a clear idea of whether face masks were actually effective against SARS-CoV-2.
But there has been reason to think masks would at least be somewhat affective, based on studies of the spread of droplets of material we expel while coughing or sneezing. And a recent analysis suggested a large group of individual studies collectively pointed to their effectiveness. But that analysis left a large degree of uncertainty about how effective they'd be at the population level and how face mask use would interact with other policy decisions.
The situation left us needing population-level modeling, which a group of UK scientists has now provided. The group's model indicates that face masks don't have to be especially effective to slow the spread of SARS-CoV-2 and can even bring benefits if they make people more vulnerable to infection. But to really control the pandemic, they will have to be combined with a lockdown if we want to see the total infected population shrink.
[...] Right now, we just don't know enough about SARS-CoV-2 and protective gear to evaluate which of these models best reflect reality. But the models do set some reasonable bounds about what we might aim for. For example, they indicate that masks don't need to be especially good if we get enough people wearing them and couple their use to other policy initiatives.
Journal Reference:
Stutt, R., Retkure, R., Bradley, M., Gilligan, C., and 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 (2020) (DOI: 10.1098/rspa.2020.0376)
(Score: 2) by Rich on Sunday June 14 2020, @09:51PM
Mike Osterholm from the CIDRAP - Center for Infectious Disease Research and Policy, University of Minnesota, Minneapolis, MN, Podcast:
(Critical of cloth masks, but very supportive of mass-deployed special N95 masks)
https://www.cidrap.umn.edu/sites/default/files/public/downloads/special_episode_masks_6.2.20_0.pdf [umn.edu]
Timo Mitze et al.: Face Masks Considerably Reduce COVID-19 Cases in Germany: A Synthetic Control Method Approach
(Mostly math modeling how masks brought down the spread in the city of Jena)
http://ftp.iza.org/dp13319.pdf [iza.org]
Renyi Zhang et al.: Identifying airborne transmission as the dominant route for the spread of COVID-19
(Very supportive of any kind of face covering)
https://www.pnas.org/content/pnas/early/2020/06/10/2009637117.full.pdf [pnas.org]
Osterholm brings very valid expertise, but might have to investigate further to explain the rather sound looking findings of the other papers. I am entirely with him on the "Volksmaske" idea, which shouldn't be hard to make in an industrialized country. (Look in what masses e.g. cookie carton inlays are made!)
Zhang lashes out to the politicians as hard as he might get away with in a scientific paper: "It is also important to emphasize that sound science should be effectively communicated to policy makers and should constitute the prime foundation in decision-making amid this pandemic."