Short and long-term outcomes of children and adolescents hospitalized with COVID-19 or influenza: results of the AUTCOV study.

Recent literature gives different results on morbidity and mortality after COVID-19 hospitalization as compared to Influenza. In this registry-based study in Austria, we compared the short- and long-term outcomes after COVID-19 or Influenza hospitalization and associations with their baseline medication load. Data were provided on children and adolescents hospitalized with COVID-19 (sample size: 1061) in the years 2020 and 2021 or with Influenza in 2016-2021 (sample size: 2781) as well as on matched controls from the Austrian population (10,626 controls for COVID-19 and 27,634 for Influenza). The median follow-up time was 430 days in the COVID-19 and 1221 days in the Influenza group. Hospitalized children were more likely to have a larger disease burden as compared to the general population. Influenza patients were observed to be generally younger with a larger percentage of polypharmacy than those with COVID-19. No significant difference in the time to hospital discharge was found between Influenza and COVID-19 patients (HR 1.22 [95% CI 0.97-1.55], p = 0.093). The risk for readmission was significantly higher for Influenza (HR 1.23 [95% CI 1.03-1.47], p = 0.021). In-hospital mortality (COVID-19: 0.94%; Influenza: 0.22%) and 1-year mortality (COVID-19: 1.13%; Influenza: 0.31%) were observed to be higher in COVID-19 patients but severe events were generally rare. The findings suggest that COVID-19 should not generally be considered a milder disease than Influenza.