As governments implement anti-contagion practices to prevent COVID-19, UC Berkeley researchers studied the effects of such policies on the growth rate of infections across six different countries.

In the early absence of reduction policies, the growth rate of COVID-19 was about 38% per day, which roughly translates to a doubling in the number of cases every two days, according to campus doctoral candidate Sébastien Annan-Phan.

To evaluate growth rate after intervention, the researchers collected information on 1,700 different policies on the national and subnational levels, according to Kendon Bell, an economist at New Zealand-based government research institute Manaaki Whenua – Landcare Research. The effectiveness of the policies was then empirically found by comparing the growth of COVID-19 in local populations before and after their implementation, Bell said.

According to Annan-Phan, the aggregate interventions evaluated in the study averted roughly 500 million infections.

“What is really common across these countries is that they all implemented policies that were aimed at trying to keep people away from each other,” Bell said.

Some of the policy actions evaluated include travel restrictions and physical distancing through quarantine, home isolation and the cancellation of gatherings, as well as other miscellaneous policies such as providing paid sick leave, according to Annan-Phan. In the United States, interventions such as home isolation and business closure were most effective in slowing the spread of the disease, according to campus doctoral candidate Esther Rolf.

In other countries, prevention methods such as business closures and travel bans also had significant impacts, according to Rolf. With an interdisciplinary and international research team, the study looked at policies that were enacted in China, South Korea, Italy, Iran and France, as well as the United States, Rolf noted.

“Which policies are effective in different countries can vary, and part of that may be due to different social norms in different countries,” Rolf said. “What we do see that’s very consistent across countries is that in aggregate, all of these policies are slowing the spread of the disease.”

Despite some differences, the main commonality across the studied countries is that they went through some form of a lockdown — except South Korea — and closed down schools, according to Bell.

The findings of this study may help guide future policies in the more than 180 other countries where COVID-19 has been reported, according to the study’s abstract. The research gives insight into when policies should be intensified or lifted, it adds.

“We see the economic impact and jobs lost, but it’s much harder to see the positive effects of these policies in terms of cases of COVID that were averted or delayed,” Rolf said.

While recent policies have intensely affected the economy and people’s personal lives, they do have strong beneficial impacts on public health and slowing the spread of COVID-19, according to Rolf.