Long COVID eases with time, according to a study that found about 1% of coronavirus patients had persistent symptoms for a year or more. In the first rigorous assessment of the magnitude of long COVID on a global scale, researchers found 6.2% of people who had COVID-19 in the pandemic’s first two years experienced at least one of three main groups of symptoms three months later. Of those patients, 15% were still afflicted after a year, they found. Although the probability of having chronic health problems from COVID is relatively low, the vast number of cases — at least 670 million worldwide — leaves a substantial burden of disability, said Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, where the study was conducted.