A comparative analysis of the outcomes of patients with influenza or COVID-19 in a tertiary hospital in Belgium

Introduction: The COVID-19 pandemic has emerged as a global health problem, associated with high morbidity and mortality rates. The aim of this study was to compare the outcomes of hospitalized patients with COVID-19 or with seasonal influenza in a teaching hospital in Belgium.Methods: In this retrospective, single-center cohort study, 1384 patients with COVID-19 and 226 patients with influenza were matched using a propensity score with a ratio of 3:1. Primary outcomes included admission to intensive care unit (ICU), intubation rates, hospital length of stay, readmissions within 30 days and in-hospital mortality. Secondary outcomes included pulmonary bacterial superinfection, cardiovascular complications and ECMO. Results: Based on the analysis of the matched sample, patients with influenza had an increased risk of readmission within 30 days (Risk Difference (RD): 0.07, 95% CI: 0.03 to 0.11) and admission to intensive care unit (RD: 0.09, 95% CI: 0.03 to 0.15) compared with those with COVID-19. Patients with influenza had also more pulmonary bacterial superinfections (46.2% vs 7.4%) and more cardiovascular complications (32% vs 3.9%) than patients with COVID-19.However, a two-fold increased risk of mortality (RD:-0.10, 95% CI: 0.15 to-0.05) was observed in COVID-19 compared to influenza. ECMO was also more required among the COVID-19 patients who died than among influenza patients (5% vs 0%).Conclusions: COVID-19 is associated with a higher in-hospital mortality compared to influenza infection, despite a high rate of ICU admission in the influenza group. These findings highlighted that the severity of hospitalized patients with influenza should not be underestimated.