One study conducted by researchers at the University of California, Berkeley examined interventions taken by six countries and found that about 531 million cases of COVID-19 were prevented or delayed. And the other study, conducted by Imperial College London, found that in 11 European countries, the virus transmission was extremely reduced and about 3.1 million lives were saved. But the researchers note that the pandemic is still ongoing, so these successes are contingent on people continuing to be careful.
The findings suggest that “these control measures have worked,” North Carolina State University mathematical epidemiologist Alun Lloyd tells Science News’ Erin Garcia de Jesus. Lloyd, who wasn’t involved in either study, adds that lockdowns “have saved or delayed many infections and deaths.”
The first article from UC Berkeley analyzes data from China, Iran, South Korea, Italy, France and the United States for about a month and a half each. The earliest data came from mid-January in China, and none of the data analyzed was collected later than April 6. Based on epidemiological modeling, the team found that in the United States, about 60 million cases of COVID-19 were averted by lockdown and social distancing measures, per a statement.
The team also tried to tease out the specific measures that had the greatest impact on reducing transmission of the coronavirus. The models did not give strong evidence that school closures made a sizeable difference, but “in some contexts, schools were actually closed already during the period when we started analyzing the data,” UC Berkeley data scientist Solomon Hsiang tells Science News. That makes it difficult to tell how infections would have spread if schools had stayed open.
But they found that home isolation, business closures and regional lockdowns did the most to slow the pandemic’s spread.
“The risk of a second wave happening if all interventions and all precautions are abandoned is very real,” Samir Bhatt, who co-led the study of European countries done at Imperial College London, told reporters during a briefing, per Reuters’ Kate Kelland.
In the study of 11 European countries, researchers estimate that more than 3 million deaths were averted by lockdown measures. Per the Guardian’s Ian Sample, this estimate is based on the fact that people sick with COVID-19 infected 81 percent fewer people than they would have if business had continued as usual. The researchers also found that under lockdown measures, the transmission of COVID-19 was reduced so much that people carrying the virus don’t always pass it to others.
However, the virus has also not infected enough people to create a natural herd immunity that can protect the population. That would require more than 70 percent of the population to have immunity to the virus, but the researchers found that the country with the most infections per capita, Belgium, was at only eight percent. Less than one percent of people in Norway and Germany have been infected with the novel coronavirus, and about five percent of people in the U.K. have.
Lloyd tells Science News that because a variety of public health measures were taken at the same time, it is difficult to disentangle exactly how helpful each individual measure was. But to Hsiang, it is clear that they helped.
“Without these policies deployed,” Hsiang said during the briefing, per Science News, “we would have lived through a very different April and May.”