Updated: Jun 14
The Lancet just published a paper presenting a meta-analysis to quantify the mitigative effect of mask wearing and social distancing in preventing spread of betacoronaviruses, including the viruses leading to COVID-19, SARS, and MERS.
They identified 44 relevant studies, cumulative including 25,697 patients with COVID-19, SARS, or MERS. some from hospitals, that looked at viral transmission based on distance from infected individual and wearing of masks of various kinds. These studies and the data are well-documented, unlike the recent notorious Lancet study.
They performed a rigorous meta-analysis across these studies, and found that distances of 1m or more suppressed infection rates by 70-80% or more, N95 masks suppressed >95% of spread, and lesser masks such as surgical or cloth masked still suppressed 80% of the spread.
These results join a growing literature supporting the mitigating effects of mask-wearing including this preprint and this Nature Medicine paper, and also provide some quantitative evidence for the benefit of basic social distancing. BTW another just-published paper in PNAS also provides support for mask-wearing.
It is welcome to see empirical and scientific evidence to document and quantifying the degree to which viral spread can be suppressed by targeted mitigation strategies like mask wearing and basic social distancing. It is possible that these basic precautions, if widely practiced, may be sufficient to limit viral spread without having resort to lockdowns again. This is particularly important looking ahead to the fall and considering how to respond to any potentially emerging second wave.