Intended for healthcare professionals


Lockdown-type measures look effective against covid-19

BMJ 2020; 370 doi: (Published 15 July 2020) Cite this as: BMJ 2020;370:m2809

Linked Research

Physical distancing interventions and incidence of coronavirus disease 2019

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  1. Thomas May, Floyd and Judy Rogers endowed professor
  1. Elson S Floyd College of Medicine, Washington State University, WA, USA
  1. thomas.may{at}

But evidence is undermined by unreliable data on incidence

The linked paper by Islam and colleagues (doi:10.1136/bmj.m2743) provides important preliminary evidence for the effectiveness of physical distancing (referred to by some as social distancing) measures in controlling the coronavirus disease 2019 (covid-19) pandemic, including closures of schools and workplaces, restrictions on mass gatherings and public events, and restrictions on movement (lockdowns).1 This supporting evidence is desperately needed as these measures are challenged around the world.

The greatest strength of this study is its reliance not on hypothetical modeling but on actual data. Although the use of some modeling techniques remained necessary, for example, to establish “controls” specific to each country, primary data reflected actual test results. Unfortunately, using such results is also the study’s greatest weakness, making analysis dependent on the quality of the data from testing. Specifically, the authors relied on “daily reported cases” compiled from 149 independent countries; data subject to variable quality, accuracy, and inconsistent testing practices.

As a result, caution is warranted when interpreting the findings. These flaws are not the fault of the authors, who have done admirable work with the information available. But the collection …

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