“Long COVID has been linked to many long-term health effects. Some commonly used study designs can misattribute symptoms to long COVID when they are actually due to non-COVID conditions that prompted care-seeking and testing. Drawing from a nationwide database of insurance claims, we mitigate this selective-testing bias using a study design that restricts analyses to individuals who sought PCR testing. With this design, known acute COVID symptoms are detected, but the number and duration of long-term outcomes attributable to COVID-19 is substantially smaller and shorter than in high profile prior reports.”

From PNAS.