 Post-acute sequelae of Covid-19, PASC, or long Covid, has caused concern but the burden and risk factors are not well understood. Here, the authors use US electronic health record data and estimate an overall burden of PASC of 7% at 6 months, with variation by severity of acute infection, baseline health status and demographics. This article was authored by Yang Xie, Benjamin Boe, and Ziad Olali.