Research Press Release

Social science: Assessing the effects of anti-contagion policies on the COVID-19 pandemic

Nature

June 8, 2020

The effects of large-scale anti-contagion policies, such as lockdowns and travel restrictions, that have been implemented by governments to slow down the rate of infections with SARS-CoV-2 are quantified for six countries in a paper published online in Nature today. The authors use econometric methods to determine the health benefits of these policies, and find that the interventions may have prevented or delayed around 62 million confirmed cases of COVID-19 across the six countries.

Throughout the current pandemic, governments worldwide have introduced diverse social policies — which can have considerable social and economic costs — including lockdowns, travel restrictions and closures of schools and businesses. These measures try to reduce the transmission of the SARS-CoV-2 virus by limiting contact among people. However, although epidemiological modelling can inform decisions about which measures to adopt, the direct assessment of the effects of these policies on infection rates is challenging.

Solomon Hsiang and colleagues analysed data on the daily infection rates of SARS-CoV-2, COVID-19 case definitions and the timing of anti-contagion policies implemented up until 6 April 2020 in China, South Korea, Italy, Iran, France and the United States. They compared the infection growth rates before and after the implementation of more than 1,700 local, regional and national policies in these countries.

They found that without anti-contagion policies in place, early infection rates of SARS-CoV-2 grew by 68% per day in Iran and an average of 38% per day across the other five countries. Using econometric modelling typically applied to assessing how policies affect economic growth, the authors show that large-scale social policies have substantially slowed the growth rate of SARS-CoV-2 infections, with measurable beneficial health outcomes in most cases. They estimate that across the six studied countries, the policy packages prevented or delayed some 62 million confirmed cases, corresponding to averting around 530 million total infections.

The authors suggest that they will be able to further refine their findings as more regional data become available, but when combined with epidemiological simulations, these empirical observations could help to inform governments as they evaluate whether and when to extend or lift these policies.

doi:10.1038/s41586-020-2404-8

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