Correlates of improved outcomes in patients with COVID-19 treated in US emergency departments

Background: The COVID-19 pandemic was managed in part by the rapid development of vaccines, diagnostics, and therapeutics including antiviral agents and advances in emergency airway and ventilatory management. The impact of these therapeutic advances on clinically pertinent metrics of emergency care have not been well-studied. Methods: We abstracted data from emergency department (ED) visits made to 21 US health systems during the first two years of the pandemic, from February 1, 2020 to January 31, 2022. These health systems were participants in the NIH-supported COVID EHR Cohort, in which the University of Wisconsin served as the coordinating site. Limited patient-level data files were submitted monthly. Data elements included demographic and clinical variables, as well as standard measures of ED outcomes including 72-h returns, 72-h returns leading to readmission, and in-hospital mortality. Multivariable models were fitted to identify correlates of each of the dependent variables. A test for trend was used to detect changes in outcomes over time. Results: During the two-year period, 150,357 individuals aged 18 years or older visited the ED. The median age was 45.4 years (IQR 27), 58.1 % were female, 49 % were White, 18.3 % Hispanic/Latino, and 45 % were publicly insured or uninsured. The prevalence of 72-h ED returns, readmissions, and in-hospital mortality significantly declined across the two-year period. SARS-CoV-2 vaccination was associated with reduced ED returns and mortality. Therapeutic agents were associated with increased mortality risk but were likely confounded by unmeasured covariates. Conclusions: Operational and clinical outcomes of ED-based treatment of individuals with COVID-19 improved in the first two years of the pandemic. This improvement is likely multifactorial and includes the development and deployment of SARS-CoV-2-specific vaccines, therapeutic agents, and improved healthcare delivery in the ED and elsewhere addressing management of airway and ventilatory status, as well as increased innate immunity in the general population.