As of September, the vast majority of U.S. residents still had not been exposed to the new coronavirus, antibody test results suggest. In all 50 states, the District of Columbia and Puerto Rico, researchers looked for COVID-19 antibodies in nearly 178,000 blood samples collected between July and September from patients undergoing tests for non-coronavirus-related reasons. In all but a few states, antibody levels suggested that less than 10% of the population had been infected with or recovered from COVID-19, researchers reported in JAMA Internal Medicine. The highest prevalence of COVID-19 antibodies was in New York - the early epicenter of the U.S. outbreak - where about 25% of blood samples were positive by mid-August. In some states, the proportion of people with COVID-19 antibodies appeared to be below 1%. Seroprevalence rates tended to wane over time, researchers found, although they rose in some states, including Georgia and Minnesota. The researchers said more work is needed to know whether and how the presence of antibodies affect people's vulnerability to COVID-19 reinfection. —Reuters Staff Source
