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Science Brief: Evidence Used to Update the List of Underlying Medical Conditions Associated with Higher Risk for Severe COVID-19

Science Brief: Evidence Used to Update the List of Underlying Medical Conditions Associated with Higher Risk for Severe COVID-19
Updated June 15, 2022

COVID-19 Science Briefs provide a summary of the scientific evidence used to inform specific CDC guidance and recommendations. The Science Briefs reflect the scientific evidence, and CDC’s understanding of it, on a specific topic at the time of the Brief’s publication. Though CDC seeks to update Science Briefs when and as appropriate, given ongoing changes in scientific evidence an individual Science Brief might not reflect CDC’s current understanding of that topic. As scientific evidence and available information on COVID-19 change, Science Briefs will be systematically archived as historic reference materials.

Page First Published May 25, 2020 | View Page Updates

Overview

CDC continues to learn about COVID-19 and associated underlying medical conditions that put people ages 18 years and older at higher risk of severe illness. Severe illness from COVID-19 is defined here as hospitalization, admission to the intensive care unit (ICU), intubation or mechanical ventilation, or death. Evidence used to inform the list of underlying conditions was determined by CDC reviewers based on available literature about COVID-19 at time of review. Literature includes published reports, scientific articles in press, unreviewed pre-prints, and data from CDC-led investigations.

The methods used to assess the conditions have changed during the pandemic as the amount of literature and types of studies increased. For instance, preliminary versions of this list focused on providing the latest information based on descriptive data. As the literature grew, CDC investigators categorized the literature by study design.

Since May 2021, the process has been updated to include a CDC-led review process that uses rigorous systematic review methods. To learn more about the process of CDC’s systematic reviews, see CDC systematic review process.

The Table of Evidence below only lists underlying conditions that are associated with severe COVID-19 outcomes.

Table of Evidence

Evidence used to inform the list of underlying medical conditions that increase a person’s risk of severe illness from COVID-19, in alphabetic order by study design section. Conditions were categorized as higher risk, suggestive higher risk, and mixed evidence.

Higher Risk (conclusive)

Higher risk for underlying conditions is defined as having a published meta-analysis or systematic review or completing the CDC systematic review process. The meta-analysis or systematic review demonstrates a conclusive increase in risk for at least one severe COVID-19 outcome.

Evidence used to update the list of underlying medical conditions that increase a person’s risk of severe illness from COVID-19
Condition Evidence of Impact on COVID-19 Severity [Reference number]
Asthma CDC systematic review [K]
Bronchiectasis CDC systematic review [A]
Cancer Meta-Analysis/ Systematic Review [1-5]
Cohort Study [6-8]
Case Series [9-11]
Case Control Study [12]
Cerebrovascular disease Meta-Analysis [13-16]
Synthesis of Evidence [17]
Cohort Study [18-20]
Chronic kidney disease Meta-Analysis [16,21]
Cohort Studies [19,22-43], [44]*
Case Series [45-47]
Chronic liver disease (cirrhosis, non-alcoholic fatty liver disease, alcoholic liver disease, autoimmune hepatitis) CDC systematic review [B]
COPD CDC systematic review [L]
Cystic fibrosis CDC systematic review [M]
Diabetes mellitus, type 1 Meta-Analysis [87]
Case Series [46]
Cohort Study [18,88-93]
Diabetes mellitus, type 2 Meta-Analysis [94]
Systematic Review [95]*
Gestational Diabetes Systematic Review [96] *
Case Series [46]
Longitudinal Study [97]
Cohort Study [87,91,97-102]
Disabilities, including Down Syndrome CDC systematic review [C]
HIV Meta-Analysis/ Systematic Review [103]
Cohort Study [35,104-106]
Case Series [107-109]
Heart conditions (such as heart failure, coronary artery disease, or cardiomyopathies) Meta-Analysis [110-112]
Cohort Study [18,19]
Interstitial lung disease CDC systematic review [D]
Mental health conditions (such as mood disorders, including depression, and schizophrenia spectrum disorders) Meta-analysis/ systematic review [117,118]
Neurologic conditions (Dementia) Meta-Analysis/ Systematic Review [119-122]
Cross-Sectional Study [123]
Cohort Study [19,124]
Obesity Meta-Analysis [125-127]
Systematic Review [95]*
Cohort [27,128-136], [44,137-140]*
Physical Inactivity CDC systematic review [E]
Pregnancy and Recent Pregnancy Meta-Analysis/ Systematic Review [95,141]
Case Control [142,143]
Case Series [144-146]
Cohort Study [147-150]
Primary Immunodeficiencies CDC systematic review [F]
Pulmonary hypertension and pulmonary embolism CDC systematic review [G]
Smoking, current and former Meta-Analysis [78,111,151-158]
Solid organ or blood stem cell transplantation Meta-Analysis [134]
Case Series [159-170]
Cohort [171-174]
Tuberculosis CDC systematic review [H]
Use of corticosteroids or other immunosuppressive medications Meta-Analysis/ Systematic Review [175]
Cohort Study [176]
Cross-Sectional [177]
Case Series [178-180]

Suggestive Higher Risk

Suggestive higher risk for underlying conditions is defined as not having a published meta-analysis or systematic review or completing the CDC systematic review process. The evidence is supported by mostly cohort, case-control, or cross-sectional studies. (Systematic reviews are available for some conditions for children with underlying conditions.)

Evidence used to update the list of underlying medical conditions that increase a person’s risk of severe illness from COVID-19
Condition Evidence of Impact on COVID-19 Severity [Reference number]
Children with certain underlying conditions Systematic Review [181,182]
Cross-Sectional Study 123,183,184]
Cohort Study [124,185-192]
Case Series [193,194]
Overweight Cohort Study [131]
Case Series [136]
Sickle cell disease Cohort [193-196]
Case Series [193,196-211]
Substance use disorders Case-Control Study [212-214]
Cohort Study [215,216]

Mixed Evidence (inconclusive: no conclusions can be drawn from the evidence)

Mixed evidence is defined as an underlying medical condition or risk factor that has a published meta-analysis or systematic review or completing the CDC systematic review process. The meta-analysis or systematic review is inconclusive, either because the aggregated data on the association between an underlying condition and severe COVID-19 outcomes are inconsistent in direction or there are insufficient data (or limited) on the association between an underlying conditions and severe COVID-19 outcomes.

  • Limited: The evidence consists of one study, or several small studies with no comparison group limiting the conclusions that can be drawn.
  • Inconsistent: The evidence suggests no clear direction of association, meaning no firm conclusions can be drawn.
Evidence used to update the list of underlying medical conditions that increase a person’s risk of severe illness from COVID-19
Condition Evidence of Impact on COVID-19 Severity [Reference number]
Alpha 1 antitrypsin deficiency Limited: CDC systematic review [I]
Bronchopulmonary dysplasia Limited: CDC systematic review [J]
Hepatitis B Inconsistent: CDC systematic review [B]
Hepatitis C Limited: CDC systematic review [B]
Hypertension Inconsistent
Meta-Analysis [111,222-225]
Systematic Review [226], [95]*
Cohort Study [18,19,22,227-234]
Case Series [235]
Thalassemia Limited: CDC systematic review [N]

Footnote: { }* indicates pregnancy–related reference.

Summary of Updates

References