Stay-at-Home Orders Correlated With Slower COVID-19 Spread
What your doctor is reading on Medscape.com:
MAY 15, 2020 — As many states begin to relax their social distancing measures and open up their economies, two studies suggest that government stay-at-home orders have had a significant impact on slowing the spread of COVID-19.
A study published today in the Journal of the American Medical Association found a significant difference in growth in the number of COVID-19 cases between border counties in Illinois, which has a stay-at-home order, and Iowa, which does not. The other study, published in Health Affairs on May 14, measured the degree to which shelter-in-place orders have decreased the spread of the virus, compared with other social distancing measures.
The JAMA study, which used a cross-sectional approach with a difference-in-differences design, compared daily changes in COVID-19 cases per 10,000 residents in eight Iowa counties that border Illinois with those in seven Illinois counties that border Iowa before and after March 21, when Illinois issued a stay-at-home order. Iowa is one of five states that do not have a stay-at-home order.
The case rates per 10,000 residents were similar in the border counties of both states before the Illinois order. After the order went into effect, the number of cases increased more quickly in Iowa and more slowly in Illinois.
Within 10, 20, and 30 days after the enactment of the stay-at-home order in Illinois, the difference in cases between the two areas, respectively, was −0.51 per 10,000 residents (P < .001), −1.15 per 10,000 residents (P = .02), and −4.71 per 10,000 residents (P = .02).
The researchers estimate that there might have been as many as 217 excess cases in the Iowa border counties after 1 month without a stay-at-home order. This estimate of excess cases, they say, represents 30.4% of the 716 total cases in the Iowa counties by that date.
This is the upper bound of the potential difference in cases had a stay-in-home order been in place in Iowa, George Wehby, PhD, a professor of health economics and health services research at the University of Iowa and one of the study’s authors, told Medscape Medical News. He cautioned that there was “a lot of uncertainty in the evidence. Other factors could have come into play.”
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