Empirical Assessment of Mandatory Stay-at-Home and Business Closure Effects on the Spread of COVID-19

Abstract

Background: The most restrictive non-pharmaceutical interventions (NPIs) for controlling the spread of COVID-19 are mandatory stay-at-home and business closures. Given the potential health and social harms of these policies, it is important to assess their effects. Here we evaluate the effects on epidemic case growth of more restrictive NPIs (mrNPIs), above and beyond the effects of less restrictive NPIs (lrNPIs).Methods: We first estimate changes in the growth of new cases during the first wave of COVID-19 in relation to the location and timing of NPI implementation in subnational regions of 10 countries: England, France, Germany, Iran, Italy, the Netherlands, Spain, South Korea, Sweden, and the United States. We isolate the effects of mrNPIs by netting out the combined effects of lrNPIs and the underlying epidemic dynamics from the effects of all NPIs. We use case growth patterns in Sweden and South Korea, two countries that did not implement mandatory stay-at-home and business closures to estimate the combined effects of lrNPIs and the underlying epidemic. We use first-difference reduced-form linear models with fixed effects, and isolate the effects of mrNPIs by subtracting the combined effects of lrNPIs in South Korea and Sweden, separately (8 mrNPI countries x 2 comparison countries = 16 comparisons).Findings: Implementing any kind of NPIs was associated with significant reductions in case growth in 9 out the 10 study countries, including the two countries that implemented only lrNPIs, South Korea and Sweden. Spain had a non-significant beneficial effect of NPIs. After netting out the combined epidemic and lrNPI effects, we find no clear, significant beneficial effect of mrNPIs on case growth in any country. In France, for example, we estimate that, after accounting for lrNPIs, the effects of mrNPIs was +7% (95CI -5%-19%) when compared with Sweden, and +13% (-12%-38%) when compared to South Korea (positive numbers indicate net pro-contagion effect). The 95% confidence intervals excluded 30% declines in all 16 comparisons and 15% declines in 11/16 comparisons.Conclusions: While small benefits cannot be excluded, mandatory stay-at-home and business closure orders do not seem to have had substantial benefits on case growth in 8 countries in the early stages of the pandemic. Similar reductions in case growth may be achievable with behavior changes from less restrictive interventions.Funding: The work was supported by the Stanford COVID-19 Seroprevalence Studies Fund.Conflict of Interest: No conflicts to declare.Ethical Approval: This study used only publicly available secondary data and was exempt from human subjects research review.