Two new papers published in the journal Nature say that lockdowns put in place to slow the spread of the coronavirus were highly effective, prevented tens of millions of infections and saved millions of lives.
"Our estimates show that lockdowns had a really dramatic effect in reducing transmission," says Samir Bhatt, a senior lecturer at the Imperial College London's School of Public Health, who worked on one of the papers published in Nature.
Bhatt's team analyzed infection and death rates in 11 European nations through May 4. They estimate that an additional 3.1 million people in those countries would have died if lockdowns had not been put in place.
"Without them we believe the toll would have been huge," Bhatt says.
In addition to the paper from Bhatt and his colleagues, Nature also published a separate study from the Global Policy Lab at UC Berkeley. That study analyzed lockdowns in China, South Korea, Iran, France, Italy and the United States.
It found that the lockdowns in those six countries averted 62 million confirmed cases.
For example, in the U.S. through the first week of April, there were officially just over 360,000 confirmed cases nationwide. Without lockdowns and other interventions, the researchers at Berkeley calculate that the U.S. would have had nearly 14 times as many by April 6: more than 5 million confirmed cases. To put this in perspective, the U.S. now, two months later, is hitting the 2 million mark.
Karin Michels, professor and chair of the Department of Epidemiology at the UCLA Fielding School of Public Health, called the UC Berkeley study "solid" and "well done," reflecting what she would have expected: "that many of the measures taken made a big difference and saved many lives."
Solomon Hsiang, director of UC Berkeley's Global Policy Lab, says these unprecedented shelter-in-place orders came at an extreme economic cost. Yet when government officials were ordering them, it was unclear exactly how significant the social benefits would be.
"The value of these studies you're seeing today is that they're demonstrating what the benefits of this policy are," Hsiang said in a press call discussing the studies. "They averted tens of millions of additional infections and millions of deaths."
The two studies used different methods to calculate the number of cases averted by the lockdowns. Bhatt's team looked at reported deaths to calculate community transmission that occurred weeks before and used the change in death numbers over time to track how much the lockdowns suppressed transmission. Hsiang's group at Berkeley used economic models usually used to examine how specific policies impact economic growth. They looked at how daily transmission growth rates shifted as lockdowns went into effect. Despite their different approaches, both groups came up with similar findings.
Both sets of researchers also caution that as lockdowns start to ease around the world, public health officials still have very limited tools to combat the coronavirus.
Testing is more widely available. Social distancing has become standard at many shops. Most large gatherings at sporting events and concerts remain banned.
But the virus continues to circulate. The vast majority of people are still susceptible to COVID-19.
Maria Van Kerkhove, an epidemiologist with the World Health Organization, this week warned that the world shouldn't ease up in its efforts against this pandemic.
"I know many of us would like this to be over and I know many situations are seeing positive signs. But it is far from over," she said. "We need everyone to focus on the job at hand, which is stopping this pandemic, suppressing transmission and saving lives. There's a lot more work to do. Let's celebrate the successes but let's remain focused on the remaining work that needs to be done because unfortunately this is far from over."
Bhatt also warns that as places come out of lockdown, transmission could rapidly flare back up again without some measures in place to check it.
"We are not saying that, you know, the country needs to stay locked down forever. But it's a cost/benefit situation," Bhatt says. "The longer you stay in lockdown, the less infections you have. People aren't moving around. When you release lockdown and you go for milder interventions, economic stability can return to some degree, but you then have the rise of infections that is possible. What we are saying is that some degree of intervention [against the virus] needs to be in place."
The researchers from both papers say that people need to understand how much of an impact the lockdown measures have been having. Hsiang at Berkeley says that as difficult as this year has been, things would have been much worse if millions of people around the globe hadn't stayed home.
"Without these policies deployed," Hsiang says. "We would have lived through a very different April and May." A period so bad, he says, "that we believe it's probably almost unimaginable."
Polly Stryker of KQED contributed to this post.