Physical distancing interventions and incidence of coronavirus disease 2019: natural experiment in 149 countries

On average, implementation of any physical distancing intervention was linked to overall reduction in covid-19 incidence of 13% (IRR 0.87, 95% CI, 0.85-0.89) and earlier implementation of lockdown to larger reduction in covid-19 incidence (IRR 0.86, 0.84 to 0.89; n=105 countries)

SPS commentary:

The study examined data from countries or regions that implemented one of the five physical distancing interventions [closures of schools, workplaces, and public transport, restrictions on mass gatherings and public events, and restrictions on movement (lockdowns)] between 1 January and 30 May 2020.


According to an editorial, caution is warranted when interpreting the findings, as the researchers relied on “daily reported cases” compiled from 149 independent countries; data subject to variable quality, accuracy, and inconsistent testing practices. It suggests that the study provides support for physical distancing but cannot be definitive for these reasons. It adds that the fact effectiveness is discernible across so many different data collection strategies and locations (individual countries) is, however, strongly suggestive of the effectiveness of these measures and the study’s conclusions are probably correct, but not certain. It cautions that control strategies informed by flawed data might advance public health aims in the short term but do lasting damage to effect behavioural change through evidence in the future. Therefore, care must be taken not to mislead or overplay politically convenient findings and risk violating the public trust necessary for an effective pandemic response.


British Medical Journal

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