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This important WHO-funded review and meta-analysis from Canada's COVID-19 SURGE group (Systematic Urgent Review Group Effort) looked at the effect of three non-pharmacological interventions on coronavirus transmission:
- Physical distancing
- Face masks
- Eye protection
Why is this important?
The speed of both the global spread of SARS-CoV-2 and national responses has lead to a bundled-approach to public health interventions for which the evidence-base is still catching up. This review provides reassurance that the core recommendations are likely beneficial.
What did they do?
Reflecting the lack of data, the review group analysed research covering not just SARS-CoV-2, but also SARS and MERS, capturing 172 observational studies with over 25,000 patients in both community and healthcare settings.
What did they find?
Perhaps unsurprisingly (though reassuring!) physical distancing > 1 meter was associated with lower transmission risk (risk difference 95% CI -11.5 to -7.5%) with increasing protection as distance increased beyond 2 meters.
Face-masks were also associated with reduced transmission (risk difference 95% CI -14.3% to -15.9%, though with low certainty), as was eye protection (risk difference 95% CI -12.5% to -7.7%).
N95 masks were even more strongly associated with risk reduction, as was mask use in a health-care setting vs non-health-care. Both N95 and multi-layer surgical masks were more protective than single-layer masks.
Bottom-line?
Simple protective behavioural changes, namely physical distancing, face-mask use and eye protection, are associated with a significant risk reduction in coronavirus transmission.
“...recognize, as an aspect of health worker safety, the precautionary principle that reasonable action to reduce risk, such as the use of a fitted N95 respirator, need not await scientific certainty”.
Campbell (2006) SARS Commission final report
Keep in mind...
Most of the 172 studies reported on bundled interventions (ie. PPE and distancing) so multi-factor analysis was required to tease out the individual contributions to risk reduction. Randomised trials are still pending...
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