COVID-19 research briefs: stay-at-home and social distancing policies are effective at reducing the spread of SARS-CoV-2

Reference

Lyu W, Wehby GL. Comparison of estimated rates of coronavirus disease 2019 (covid-19) in border counties in Iowa without a stay-at-home order and border counties in Illinois with a stay-at-home order. JAMA Netw Open. Published online May 1, 2020. doi:10.1001/jamanetworkopen.2020.11102.

Synopsis

Research Brief #28: This study compared daily changes in COVID-19 cases in 8 Iowa counties that border Illinois (where no stay-at-home orders were in place) with 7 Illinois counties that border Iowa (where stay-at-home orders were in place). Sensitivity analysis was used to account for differences in other factors, such as the closing of schools and nonessential businesses, county population densities, and poverty rates. Trends in cumulative COVID-19 incidence were compared before and after March 21, 2020, the day the stay-at-home order went into effect in Illinois. At 10, 20, and 30 days after that date, the number of cases increased more quickly in the Iowa counties than in the Illinois counties, with a difference of 4.71 additional cases per 10,000 residents (95% CI -8.64 to -0.78; P = .02) at 30 days. The estimated excess cases in Iowa was as high as 217 cases during that 30 days, which represents 30.4% of the 716 cases diagnosed in those counties by that date. The sensitivity analysis supported these findings.

Research Brief #29: Clarke County, Georgia, implemented mandatory social distancing policies on March 20, 2020, 14 days prior to statewide implementation on April 3. The counties surrounding Clarke followed the statewide guidelines. Using statewide case reports by county, these investigators estimated doubling time, an accepted measure of spread of infection, for Clarke and its surrounding counties. By April 26, the 5-day rolling average doubling time was twice as long in Clarke than in surrounding counties (40 days vs 20 days). The social distancing policy that prohibited events and gatherings of more than 10 people and required individuals to remain at home, with limited exceptions for essential travel, was effective in slowing the spread of COVID-19.

Reference: Ebell MH, Bagwell-Adams G. Mandatory social distancing associated with increased doubling time: an example using hyperlocal data. Am J Prev Med. Pre-proof published online 2020. doi: https://doi.org/10.1016/j.amepre.2020.04.006.