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Lockdowns worked. Now what?

Stay-at-home orders and closing restaurants slowed Covid-19’s spread in the US, new study shows.

People practice social distancing in Domino Park in Williamsburg during the coronavirus pandemic on May 17 in New York City.
Coronavirus lockdowns and stay-at-home orders have slowed the disease’s spread in the US, a new study finds.
Noam Galai/Getty Images
Dylan Scott covers health care for Vox. He has reported on health policy for more than 10 years, writing for Governing magazine, Talking Points Memo and STAT before joining Vox in 2017.

Flattening the curve through social distancing has worked in restraining Covid-19’s growth, according to new research published in Health Affairs.

But that raises the question: What now?

Researchers from the University of Kentucky and the University of Louisville studied the effects of four different social distancing policies — school closures, closing restaurants and bars, bans on large gatherings, and shelter-in-place orders — to tease out both their individual and cumulative effects in flattening the curve. They studied the period from March 1, before any of these policies had been put into effect, to April 27, when Georgia became the first state to start relaxing its social distancing measures.

The bottom line, according to their modeling: These government interventions have worked to reduce the spread of the coronavirus.

Adoption of government-imposed social distancing measures reduced the daily growth rate by 5.4 percentage points after 1–5 days, 6.8 after 6–10 days, 8.2 after 11–15 days, and 9.1 after 16–20 days. Holding the amount of voluntary social distancing constant, these results imply 10 times greater spread by April 27 without SIPOs (10 million cases) and more than 35 times greater spread without any of the four measures (35 million).

The goal of flattening the curve was to prevent local health systems from becoming overwhelmed, which could have led to even higher fatalities than the US has already seen (about 90,000, as of Monday morning). Even New York City, the hardest-hit place in the country, has not seen its hospitals overrun in any kind of systemic way.

Take together the reduced spread through social distancing and the medical system being able to meet the Covid-19 need, and there is solid evidence that flattening the curve has worked.

One of the supplemental charts in the Health Affairs paper makes the case:

Health Affairs

“The highly visible, strong government-imposed measures achieved one key goal: dramatically reducing the spread of Covid-19 disease while allowing the health care system to not get overwhelmed,” Aaron Yelowitz, one of the University of Kentucky economists who co-wrote the paper, told me over email. “In principle, the measures also bought time to develop a more effective testing and contact tracing infrastructure, although we will see whether that actually has been achieved as states start to reopen.”

Their new research was thorough in attempting to isolate the effect of government policies specifically. They presumed some degree of voluntary social distancing even in the no-intervention scenario, and also accounted for the availability of Covid-19 testing and the differences in susceptibility to the coronavirus in various places, depending on population density and age.

The researchers could not account for every conceivable variable. They note that they do not attempt to measure how mask-wearing or closing public parks and beaches or restrictions on visits to nursing homes might affect Covid-19’s spread and impact. Nevertheless, over the period they studied, the percentage of the US population subjected to these government policies grew to 95 percent — and the effect they find on the coronavirus is sizable.

Not all of the interventions had an equal impact, however, according to the Kentucky-based economists. They found statistically significant effects from the shelter-in-place orders as well as closing bars and restaurants, but not for closing schools or banning large gatherings.

The ban on large gatherings was closer to statistical significance than the school closures and, when accounting for the imprecision of any modeling like this, it is possible those restrictions had an effect that the researchers’ simulations simply failed to measure. But the authors also floated other possibilities.

For instance, when schools were closed, kids and families might have instead had social interactions outside of school. The researchers failed to detect a meaningful change in spread between when kids were out of school or in school, despite fears that they could be asymptomatic carriers. Likewise, formal large events could have been replaced by informal ones. It’s also possible the ban on large gatherings had a limited effect because many of those events were already canceled before the government policy was actually instituted.

This could explain why the shelter-in-place orders — which would have also restricted those informal interactions — had the biggest measurable effect.

The authors say they hope their findings will help inform policymakers in deciding how to start reopening their local economies. They avoid being too prescriptive but observe that, based on what they found, keeping schools closed but lifting shelter-in-place orders would be expected to lead to cases increasing again.

Ready or not, the US is starting to reopen. I think all of us can understand people’s yearning to get life back to something resembling normalcy after two months of lockdown unlike anything any of us have experienced in our lives. And we have growing evidence that certain activities — particularly those that take place outdoors — are less risky than others. One way to alleviate all of the pent-up frustrations, as well as jumpstart the stagnated economic activity that has taken its own devastating toll, is to give people an outlet.

Research like this new Health Affairs paper provides more information about what works best and what doesn’t. They also gesture at other variables they did not measure that warrant more study, such as mask-wearing or activities at public parks. We have to seek a middle ground between maintaining the social distancing policies that have worked to slow the spread and the natural need for social interaction and the urgency of relieving the economic crisis.

But all of these discussions are undergirded by one important reality. Many people, the vast majority of us, are still susceptible to Covid-19. A sloppy end to social distancing could mean a rapid rebound in the virus’s spread.

“At issue moving forward is whether cases averted simply turn into cases delayed,” the Kentucky economists wrote, “and a premature return to light measures would make this more likely.”

This story appears in VoxCare, a newsletter from Vox on the latest twists and turns in America’s health care debate. Sign up to get VoxCare in your inbox along with more health care stats and news.

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