BACKGROUND: The economic burden of severe asthma and severe uncontrolled asthma (SUA) is significant. Updated assessments of health care resource utilization (HCRU) and cost are needed given the increase in treatment options and updates to guidelines in recent years. OBJECTIVE: To describe all-cause and asthma-related HCRU and costs among patients with SUA vs patients with nonsevere asthma in the United States using real-world data. METHODS: MarketScan administrative claims databases were used to select adults with persistent asthma for this retrospective analysis between January 1, 2013, and December 31, 2019. Asthma severity status was defined using the Global Initiative for Asthma step 4/5 criteria (index is the earliest date qualifying patients as severe or randomly assigned for nonsevere patients). Patients with SUA were a subset of the severe cohort meeting the following criteria: those who were hospitalized with asthma as the primary diagnosis or had at least 2 emergency department or outpatient visits with an asthma diagnosis and a steroid burst within 7 days. HCRU, costs (allcause and asthma-related defined as medical claims with an asthma diagnosis and pharmacy claims for asthma treatment), work loss, and indirect costs due to absenteeism and short-term disability (STD) were compared between patients with SUA, severe, and nonsevere asthma. Outcomes were reported during a fixed 12-month post-index period using chi-square and t-tests where appropriate. RESULTS: 533,172 patients with persistent asthma were identified (41.9% [223,610]) severe and 58.1% [309,562] nonsevere). Of the severe patients, 17.6% (39,380) had SUA. The mean (SD) all-cause total health care costs were significantly higher in patients with SUA ($23,353 [$40,817]) and severe asthma ($18,554 [$36,147]) compared with those with nonsevere asthma ($16,177 [$37,897], P < 0.001 vs nonsevere asthma). The results were consistent for asthma-related costs. In addition, although patients with severe asthma made up 41.9% of the total study population, they contributed disproportionately higher costs (60.5%) to the total asthma-related direct costs, with the effect more evident among patients with SUA (7.4% of study population contributed 17.7% of the total asthma-related costs). For the subset of patients with asthma with workplace absenteeism, patients with SUA lost more time from work (259.3 vs 236.2 hours lost, P = 0.002; 7.8 vs 5.3 STD days, P < 0.001), and had higher corresponding indirect costs ($5,944 vs $5,415, P = 0.002 for absenteeism related; $856 vs $582, P < 0.001 for STD related) compared with patients with nonsevere asthma. CONCLUSIONS: Patients with SUA have significantly higher asthma-related economic burden compared with patients with nonsevere asthma and contribute a disproportionally higher percentage of asthma-related costs. DISCLOSURES: This study was funded by Amgen and AstraZeneca. The design and analysis for this study was conducted primarily by Merative. Amgen and AstraZeneca provided funding to support protocol development, data analysis, and manuscript development activities associated with this study. Dr Burnette is on the advisory board and a consultant for GSK, a consultant and member of the advisory boards and speakers' bureaus of Sanofi, Genzyme, Regeneron, AstraZeneca, and Amgen Inc. Dr Wang, Dr Rane, Dr Lindsley, and Dr Llanos are employees and shareholders of Amgen Inc. Dr Chung and Dr Ambrose are employees and shareholders of AstraZeneca. Ms Princic and Ms Park are employees of Merative, which received funding from Amgen to conduct this study.