Definitional and Methodological Errors in Pediatric Post–COVID-19 Condition Research Letter

To the Editor The Research Letter by Hahn et al draws an invalid conclusion that the incidence of post–COVID-19 condition (PCC), as defined by the World Health Organization (WHO), is strikingly low in children. The authors cite an informal summary definition of PCC in their Introduction, then in the Methods section change the definition’s symptom time frame from after 3 months postinfection to within 3 months. The formal WHO definition is concerned with symptoms after 3 months, meaning the research did not study PCC as cited and cannot draw conclusions about PCC.