Lockdown, stay-at-home measures may have averted 60 million coronavirus infections in US, suggests report

Researchers estimate that restrictions in 6 countries, which includes US, China, South Korea, Italy, Iran, and France, prevented a total of 530 million Covid-19 cases in these countries


                            Lockdown, stay-at-home measures may have averted 60 million coronavirus infections in US, suggests report
(Getty Images)

Policy measures such as lockdown and stay-at-home orders may have prevented 60 million Covid-19 infections in the US and 285 million in China, according to a new study. The research team estimated the effects of 1,717 local, regional, and national non-pharmaceutical interventions implemented in the ongoing pandemic across the US, China, South Korea, Italy, Iran, and France. They found that restrictions prevented as many as 530 million infections in the six countries. The findings come as countries worldwide struggle to balance the enormous and highly visible economic costs of emergency health measures against their public health benefits, which are difficult to see.

The researchers estimate that in the absence of policy measures — such as travel restrictions, business closures, shelter-in-place orders, and other non-pharmaceutical interventions — early infection rates of Covid-19 would have grown 43% per day on average across these six countries. This implies that the number of infected people would double roughly every two days. Country-specific estimates range from 34% per day in the US to 68% per day in Iran. 

“In the absence of policy actions, we estimate that early infections of Covid-19 exhibit exponential growth rates of roughly 38% per day. We find that anti-contagion policies have significantly and substantially slowed this growth. Some policies have different impacts on different populations, but we obtain consistent evidence that the policy packages now deployed are achieving large, beneficial, and measurable health outcomes,” say researchers in their findings published in Nature

“We estimate that across these six countries, interventions prevented or delayed on the order of 62 million confirmed cases, corresponding to averting roughly 530 million total infections,” says the team, which includes experts from UC Berkeley, US; National Bureau of Economic Research & Centre for Economic Policy Research, Cambridge; and Manaaki Whenua – Landcare Research, Lincoln, New Zealand. 

The researchers estimate that in the absence of policy measures and other non-pharmaceutical interventions, early infection rates of Covid-19 would have grown 43% per day on average across the six countries studied. (Getty Images)

The team studied how quickly the number of Covid-19 infections grew within different locations before and after policies were enacted, measuring how much each policy contributed to flattening the curve. The researchers analyzed data on the number of confirmed cases in each country, based on local testing procedures. But to account for limited testing, they also calculated what the total infection rates likely would have been if everyone had been tested. The study did not estimate how many lives might have been saved by the policies.

The researchers explain that due to the lockdown measures in place, the countries managed to avoid 62 million “confirmed cases” of Covid-19, including 4.8 million in the US. Since many infections are not formally diagnosed due to limited testing, the researchers estimate that restrictions prevented as many as 530 million infections across the six countries in the study period ending April 6. 

The estimates suggest that there would be roughly 37 million more cumulative confirmed cases (corresponding to 285 million more total infections, including the confirmed cases) in China, 11.5 million more confirmed cases in South Korea (38 million total infections), 2.1 million more confirmed cases in Italy (49 million total infections), 5 million more confirmed cases in Iran (54 million total infections), 1.4 million more confirmed cases in France (45 million total infections), and 4.8 million more confirmed cases (60 million total infections) in the US had these countries never enacted any anti-contagion policies since the start of the pandemic. The results suggest that ongoing anti-contagion policies have already substantially reduced the number of Covid-19 infections observed in the world today, says the team.

The team found that home isolation, business closures and lockdowns often produced the clearest benefits. Travel restrictions and bans on gathering had mixed results, with large effects in some countries — Iran and France, respectively, for example — and less clear benefits in countries such as the US. The researchers did not find strong evidence that school closures had an impact in any country, but they cautioned that their finding is not conclusive and that more research should be used to inform school policies.

“The last several months have been extraordinarily difficult, but through our individual sacrifices, people everywhere have each contributed to one of humanity’s greatest collective achievements. I don’t think any human endeavor has ever saved so many lives in such a short period. There have been huge personal costs to staying home and canceling events, but the data show that each day made a profound difference. By using science and cooperating, we changed the course of history,” says lead author Solomon Hsiang, director of Berkeley’s Global Policy Laboratory and Chancellor’s Professor at the Goldman School of Public Policy, in the analysis.

The researchers did not find strong evidence that school closures had an impact in any country, but caution that their finding is not conclusive, and more research is needed to inform school policies. (Getty Images)

Lockdown in Europe may have saved 3.1M lives

A separate study that analyzed the impact of major interventions across 11 European countries for the period from the start of Covid-19 until May 4, when lockdown started to be lifted, estimates that approximately 3.1 million deaths have been averted due to non-pharmaceutical measures. The team from Imperial College London estimated that by May 4, between 12 and 15 million individuals in these countries had been infected with SARS-CoV-2, the virus that causes Covid-19, representing 3.2% to 4% of the population, with large country-to-country fluctuations. The findings have been published in Nature.

The Imperial team used death data to infer changes in the course of the Covid-19 epidemic as a result of non-pharmaceutical interventions. They analyzed data from the UK, Austria, Belgium, Denmark, France, Germany, Italy, Norway, Spain, Sweden, and Switzerland. By comparing the number of observed deaths against those predicted by their model in the absence of interventions, the authors suggest that approximately 3.1 million deaths have been averted due to measures. They calculated that the reproduction number dropped to below one as a result of the interventions, decreasing by an average of 82%, although the values vary from country to country.

“This data suggests that without any interventions, such as lockdown and school closures, there could have been many more deaths from Covid-19. The rate of transmission has declined from high levels to ones under control in all European countries we study. Our analysis also suggests far more infections in these European countries than previously estimated. Careful consideration should now be given to the continued measures that are needed to keep SARS-CoV-2 transmission under control,” says Dr Samir Bhatt, study author from the MRC Centre for Global Infectious Disease Analysis, Jameel Institute (J-IDEA), Imperial College London, in the analysis.

As of June 9, more than 7,118,470 coronavirus cases have been reported worldwide, and over 406,520 have died in the Covid-19 pandemic. 

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