Popularization of research advances on COVID-19

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Is lockdown necessary?

In order to fight against COVID-19, governments have taken a number of public health measures, such as lockdowns or the closure of “non-essential” businesses. Little is known of the effectiveness of such measures, as several of them tend to be put in place at the same time, and it is difficult to estimate the effectiveness of each one of them. However, such evaluation is very important to governments to help them in their choices and so that they put in place only such measures that work, so as to minimize restrictions on public activity.

An international study has evaluated the impact of several measures enforced by the governments of 41 countries (34 European and 7 non-European) during the 1st wave (between the 22nd of January and the 30th of May 2020). Since the same measures were not put in place at the same time, it is possible, through analysis and modelling, to estimate the efficiency of each of these measures individually. To do so, the number of cases of infection by SARS-CoV-2 and the number of deaths was measured. This data allowed the calculation of the number of new infections in a given period and thereby the level of reproduction of the virus (called the R0, representing the capacity for transmission of a pathogen). The scientists then attributed an effectiveness score to each measure, according to the percentage reduction in the R0. So a measure with modest effectiveness allows a reduction in the R0 of 15,5%; a measure with moderate effectiveness allows a reduction of 17,5%, and with major effectiveness more than 35% reduction in the R0.

This study shows that the most effective measures were the banning of public gatherings of more than 10 people (reduction of the R0 by between 17 to 60%) and the closure of schools and colleges (reduction of the R0 by between 16 to 54%). The closure of “non-essential” businesses seems to have moderate effectiveness (reduction of the R0 by between 3 to 49%). In addition, the combination of 2 measures enables greater effectiveness.

What about lockdown specifically? This sanitary measure has been applied when other measures were already in place. Contrary to what we might imagine, it seems that its effectiveness is only modest (reduction of the R0 by between 5 to 31%, in addition to the effectiveness of the other measures).

This can be schematically represented as follows:

Even if these results can help governments decide about which measures to apply, it must be borne in mind that their effectiveness also depends on the context of their application (on the demography of a particular area, for example).

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