Governments around the world are responding to the coronavirus disease 2019 (COVID-19)
pandemic1, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2),
with unprecedented policies designed to slow the growth rate of infections. Many policies,
such as closing schools and restricting populations to their homes, impose large and
visible costs on society; however, their benefits cannot be directly observed and
are currently understood only through process-based simulations2-4. Here we compile
data on 1,700 local, regional and national non-pharmaceutical interventions that were
deployed in the ongoing pandemic across localities in China, South Korea, Italy, Iran,
France and the United States. We then apply reduced-form econometric methods, commonly
used to measure the effect of policies on economic growth5,6, to empirically evaluate
the effect that these anti-contagion policies have had on the growth rate of infections.
In the absence of policy actions, we estimate that early infections of COVID-19 exhibit
exponential growth rates of approximately 38% per day. We find that anti-contagion
policies have significantly and substantially slowed this growth. Some policies have
different effects on different populations, but we obtain consistent evidence that
the policy packages that were deployed to reduce the rate of transmission achieved
large, beneficial and measurable health outcomes. We estimate that across these 6
countries, interventions prevented or delayed on the order of 61 million confirmed
cases, corresponding to averting approximately 495 million total infections. These
findings may help to inform decisions regarding whether or when these policies should
be deployed, intensified or lifted, and they can support policy-making in the more
than 180 other countries in which COVID-19 has been reported7.