Evidence used to update the list of underlying medical conditions that increase a person\u2019s risk of severe illness from COVID-19

Updates to the list of underlying medical conditions that put individuals at increased risk for severe illness from COVID-19 were based on published reports, articles in press, unreviewed pre-prints, and internal data available between December 1, 2019 and May 29, 2020. This list is a living document that will be periodically updated by CDC, and it could rapidly change as the science evolves. Severe illness from COVID-19 was defined as hospitalization, admission to the ICU, intubation or mechanical ventilation, or death.The level of evidence for each condition was determined by CDC reviewers based on available information about COVID-19. Conditions were added to the list (if not already on the previous underlying medical conditions list [originally released in March 2020]) if evidence for an association with severe illness from COVID-19 met any of the following criteria:\u2022 Strongest and most consistent evidence: Defined as consistent evidence from multiple small studies or a strong association from a large study,\u2022 Mixed evidence: Defined as multiple studies that reached different conclusions about risk associated with a condition, or\u2022 Limited evidence: Defined as consistent evidence from a small number of studies. categorization for a condition\u2019s association with severe illness from COVID-19, the condition was added to the list (if not already on the previous underlying medical conditions list [originally released in March 2020]).Qualifiers to previously listed conditions were added or removed if there was strong evidence to support that the condition be expanded. Conditions previously listed were to be removed if there was strong and consistent evidence demonstrating no association with severe outcomes. Based on this criterion, no conditions were removed from the previous underlying medical conditions list dated March 2020.2020788