IntroductionAlthough patients’ clinical conditions were previously shown to be associated with coronavirus disease 2019 (COVID-19) severity and outcomes, their impact on hospital costs is not known. The economic evaluation of COVID-19 admissions allows the assessment of hospital costs associated with the treatment of these patients, including the main cost components and costs driven by demographic and clinical conditions. The aim of this study was to determine the COVID-19 hospitalization-related costs and their association with clinical conditions.MethodsProspective observational cohort study of the hospitalization costs of patients with COVID-19 admitted between March 30 and June 30, 2020, who were followed until discharge, death, or external transfer, using micro-costing methodology. The study was carried out in the Central Institute of the Hospital das Clinicas, affiliated with the Faculty of Medicine of the University of Sao Paulo, Brazil, which is the largest hospital complex in Latin America and was designated to exclusively admit COVID-19 patients during the pandemic response.ResultsThe average cost of the 3,254 admissions (51.7% of which involved intensive care unit (ICU) stays) was US$12,637.42. Overhead cost was the main cost component, followed by daily fixed costs and drugs. Sex, age and underlying hypertension (US$14,746.77), diabetes (US$15,002.12), obesity (US$18,941.55), cancer (US$10,315.06), chronic renal failure (US$15,377.84), and rheumatic (US$17,764.61), hematologic (US$15,908.25) and neurologic diseases (US$15,257.95) were significantly associated with higher costs. Age >69 years, RT-PCR-confirmed COVID-19, comorbidities, the use of mechanical ventilation, dialysis, or surgery, and poor outcomes remained significantly associated with higher costs after model adjustment.ConclusionKnowledge of COVID-19-associated hospital costs and their impact across different populations can aid in the development of a generalizable and comprehensive approach to hospital preparedness, decision-making and planning for future risk management. Determining the disease-associated costs is the first step in evaluating the cost-effectiveness of treatments and vaccination programs.SUMMARY BOXQuestionWhat are the COVID-19 hospitalization-related costs?FindingsIn this prospective cohort that was carried out in a single reference quaternary center designated for the treatment of severe cases of COVID-19, more than three thousand patients were included, and their costs of hospitalization were found to be directly related to the age and comorbidities. The costs were more than 50% higher in older patients, 10-24% higher in patients with comorbidities, and 24-200% higher when additional therapeutic procedures were required.MeaningDetermining the disease-associated costs is the first step in conducting future evaluations of the cost-effectiveness of treatments and vaccination programs, supporting their implementation with a comprehensive population-based approach.