US cell phone data: Staying home amid lockdowns may stem COVID-19US counties with large declines in cell phone activity at workplaces, transit stations, and stores and concomitant increases in home activity during COVID-19 lockdowns had lower rates of coronavirus infections 5, 10, and 15 days later, according to a study published today in JAMA Internal Medicine.The researchers made 22,124 to 83,745 daily observations of cell phone location data from 949 to 2,740 counties, depending on data availability, from Jan 22 to May 11 and compared them with COVID-19 growth rates.Growth of COVID-19 cases was 45.5% lower in counties in the lowest quartile of activity in retail stores than in those with the highest quartile, while counties with the most