Background and Aims: The most restrictive non-pharmaceutical interventions (NPIs) for controlling
the spread of COVID-19 are mandatory stay-at-home and business closures. Given the consequences
of these policies, it is important to assess their effects. We evaluate the effects on epidemic case
growth of more restrictive NPIs (mrNPIs), above and beyond those of less restrictive NPIs (lrNPIs).
Methods: We first estimate COVID-19 case growth in relation to any NPI implementation in
subnational regions of 10 countries:
  • England
  • France
  • Germany
  • Iran
  • Italy
  • Netherlands
  • Spain
  • South Korea
  • Sweden
  • US

Using first-difference models with fixed effects, we isolate the effects of mrNPIs by subtracting the combined effects of lrNPIs and epidemic dynamics from all NPIs. We use case growth in Sweden and South Korea, two countries that did not implement mandatory stay-at-home and business closures, as comparison countries for the other 8 countries (16 total comparisons).

Results: Implementing any NPIs was associated with significant reductions in case growth in 9 out of
10 study countries, including South Korea and Sweden that implemented only lrNPIs (Spain had a
non-significant effect). After subtracting the epidemic and lrNPI effects, we find no clear, significant
beneficial effect of mrNPIs on case growth in any country. In France, e.g., the effect of mrNPIs was
+7% (95CI -5%-19%) when compared with Sweden, and +13% (-12%-38%) when compared with
South Korea (positive means pro-contagion). 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, we do not find significant benefits on case
growth of more restrictive NPIs. Similar reductions in case growth may be achievable with less
restrictive interventions.
We can be very thankful Sweden and South Korea stood up to the concerted bullying or there would have been no control group to compare lockdowns to!
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