Background: The COVID-19 pandemic has placed unprecedented pressure on hospitals worldwide. In such a context of tension in healthcare systems, efficiently allocating hospital resources is a crucial aspect of crisis management. The aim of this study was to describe the clinical characteristics of readmitted patients and to determine risk factors for hospital readmission using data from the Swiss COVID-19 Hospital-Based Surveillance system (CH-SUR).

Methods: We investigated hospital readmissions within 60 days after discharge of patients from the CH-SUR surveillance system with a first hospitalisation between 1 December 2020 and 1 December 2021. Only community-acquired cases were considered. We compared the baseline characteristics of readmitted and non-readmitted patients. We performed univariable and multivariable logistic regression analyses to investigate the risk factors for hospital readmission.

Findings: Of the 8039 eligible patients, 239 (3.0%, 95% confidence interval [CI] 2.6-3.3%) were readmitted to hospital within 60 days of discharge, with no significant variations observed over the study period; 80% of all readmissions occurred within 10 days of discharge of the index hospital stay. Based on our multivariable logistic regression models, factors increasing the odds of hospital readmission were age ≥65 years (odds ratio [OR] 1.63, 95% CI 1.24-2.15), male sex (OR 1.47, 95% CI 1.12-1.93), being discharged to home after first hospitalisation (OR 1.77, 95% CI 1.19-2.62), having oncological pathology (OR 1.82, 95% CI 1.27-2.61) and being immunosuppressed (OR 2.34, 95% CI 1.67-3.29).

Interpretations: Age, sex, cardiovascular diseases, oncological pathologies and immunosuppression were the main risk factors identified for hospital readmission.