Lockdowns prevented nearly 5 million U.S. coronavirus cases, study says

Shutdown orders to close nonessential businesses and keep most people at home over the last two months helped the U.S. avoid nearly 5 million coronavirus cases, according to a new study published Monday.

The study, which was conducted by researchers at the University of California at Berkeley, examined how 1,717 public policy interventions, from stay-at-home orders to travel bans, affected the spread of the virus in six countries: the U.S., China, South Korea, Italy, France and Iran. 

The study found that those countries managed to avoid 62 million confirmed cases of Covid-19, including 4.8 million in the U.S., by implementing so-called lockdown or stay-at-home orders. Because many infections are undetected and the virus can spread asymptomatically, the researchers estimated that restrictions actually prevented about 530 million infections in those countries — 60 million in the U.S. alone.

“Our results suggest that ongoing anti-contagion policies have already substantially reduced the number of COVID-19 infections observed in the world today,” the researchers wrote. 

When it comes to such policies, timing is key, the researchers wrote, adding that “seemingly small delays in policy deployment likely produced dramatically different health outcomes.”

In the absence of restrictive policies, the early infection rates of Covid-19 would grow 43{3c4481f38fc19dde56b7b1f4329b509c88239ba5565146922180ec5012de023f} per day on average across the six countries, the study says. That means the number of infected people would double roughly every two days. 

“During the early stages of an epidemic, a large proportion of the population remains susceptible to the virus, and if the spread of the virus is left uninhibited by policy or behavioral change, exponential growth continues until the fraction of the susceptible population declines meaningfully,” the researchers wrote. 

Such restrictive policies were made with limited information as the new virus, which emerged just over six months ago in Wuhan, China, crept across the world to the U.S., the researchers wrote. They said they conducted the study in hopes of making clear the health benefits of such policies for countries that have yet to face a large outbreak.

“Societies around the world are weighing whether the health benefits of anti-contagion policies are worth their social and economic costs,” the researchers wrote.

Further research should examine the impact of such policies on hospitalizations and deaths rather than just confirmed cases, the researchers said.