While stay-at-home orders are leading to a reduction in coronavirus cases across the country, the impact of these ordinances varies depending on when they are implemented, a new study shows.
The number of COVID-19 cases fell by up to 43.7% roughly three weeks after the implementation of a shelter-in-place order, according to a working paper distributed Monday by the National Bureau of Economic Research. The paper was authored by researchers at Bentley University, San Diego State University and the University of Colorado Denver.
Researchers analyzed social-mobility data from SafeGraph, a geospatial data company, which represents the movements of roughly 45 million smartphone devices. To produce their estimates of the effects of the shelter-in-place orders on health outcomes they drew on data regarding COVID-10 cases collected by the Centers for Disease Control and Prevention and made public by the Kaiser Family Foundation.
However, some states will see more success from their shelter-in-place orders (SIPOs) than others, the researchers wrote. “The earliest adopters of statewide SIPOs saw the largest declines in the rate of coronavirus cases, including declines in the rate of COVID-19-related mortality,” they said. “In addition, more densely populated states also appear to reap relatively larger health benefits from their SIPOs.”
People spent between 5% and 10% more time at home in states where shelter-in-place orders were put into effect. Between March 19 and April 20, 40 states and the District of Columbia implemented these orders in an effort to slow the spread of the coronavirus.
In the immediate wake of stay-at-home ordinances being put into effect, researchers found little change in the number of coronavirus cases, a reflection of the virus’ incubation period. But 15 to 19 days after an order’s adoption, coronavirus cases fell by 37.8%. After 20 days, researchers found that coronavirus cases fell by 45.1%.
The researchers performed separate analyses excluding those states with a higher numbers of coronavirus cases from the sample, including New York, New Jersey, California and Washington state. These analyses showed a similarly high reduction in COVID-19 cases following the introduction of social distancing requirements in states where fewer people had contracted the virus.
Researchers cautioned that the longer-term benefits of shelter-in-place orders — and importantly, what happens when they are lifted – aren’t yet clear.
“Some of the short-run COVID-19 cases and deaths may simply be postponed to the near future when the SIPO is lifted,” the paper’s authors wrote. “In that case, deaths and serious illnesses averted by avoiding short-run shortages of ventilators, hospital beds, and medical professionals may be a SIPO’s most likely path to generating long-run public health benefits.”
The number of cases, meanwhile, continues to rise. As of Monday, 7.1 million people had been tested in the U.S. for SARS-CoV-2. There were 1,161,804 confirmed cases, and 67,798 deaths in the U.S., of which 18,925 were in New York City. Worldwide, there were 3,534,544 confirmed cases and 248,164 deaths, according to Johns Hopkins Whiting School of Engineering.