Short-and Long-Term Outcomes following COVID-19 or Influenza Hospitalization in Adults: Results of the AUTCOV-Study

Christine Wagenlechner^1,2Ralph Wendt³Berthold Reichardt⁴Michael Mildner⁵Julia Mascherbauer⁶Clemens Aigner²Johann Auer⁷Hendrik Jan Leonard Ankersmit^2,8*Alexandra Graf¹

• ¹Medizinische Universitat Wien Zentrum fur Medical Data Science, Vienna, Austria
• ²Clinic of Thoracic Surgery, Medical University of Vienna, Vienna, Austria
• ³Department of Nephrology, Hospital St. Georg Leipzig, Leipzig, Germany
• ⁴Austrian Social Health Insurance Fund, Eisenstadt, Austria
• ⁵Clinic of Dermatology, Medical University of Vienna, Vienna, Austria
• ⁶Department of Internal Medicine 3, University Hospital St. Poelten, St. Pölten, Austria
• ⁷Department of Internal Medicine 1 with Cardiology and Intensive Care, St. Josef Hospital Braunau, Braunau, Austria
• ⁸Laboratory for Cardiac and Thoracic Diagnosis, Regeneration and Applied Immunology, Vienna, Austria

Introduction: Large-scale registry-based studies on patients hospitalized with COVID-19 as compared to Influenza are scant but needed to re-evaluate the pandemic and characteristics of patients at risk of severe outcomes. Methods: In this registry-based study from Austria, we examined short-and long-term outcomes after hospital admission due to COVID-19 or Influenza, also focusing on outcomes conditional on hospital survival. Data were provided on adults hospitalized with COVID-19 in the years 2020 and 2021 or with Influenza in 2016 – 2021 as well as on matched controls from the Austrian population. Analyses were performed separately for four age groups (19-40, 41-64, 65-74, ≥75). Results: COVID-19 and Influenza hospitalized patients had a larger medication load as compared to the general population. Over all investigated age groups, polypharmacy was more frequently for the Influenza group. The risk for all-cause death in the whole follow-up period and death during hospital stay was higher in the COVID-19 group as compared to Influenza for all age groups ≥41 years. Furthermore, duration of hospitalization was longer in COVID-19 patients. Notably, readmission rates were higher in Influenza patients and mortality of hospital survivors was increased in younger Influenza patients aged 41-64 compared to COVID. Conclusion: In the first two pandemic years, COVID-19 had devastating effects in a non-immunized population, mainly in older patients and in patients with pre-existing serious comorbidities, but the health consequences of Influenza should not be underestimated.