# Short- and long-term outcomes following COVID-19 or Influenza hospitalization in adults: results of the AUTCOV study

## TL;DR

This study compares the short- and long-term outcomes of adults hospitalized with COVID-19 or Influenza in Austria, highlighting differences in mortality, hospitalization duration, and readmission rates.

## Contribution

The study provides a large-scale registry-based comparison of hospitalized COVID-19 and Influenza patients in Austria, focusing on age-specific outcomes.

## Key findings

- Hospitalized COVID-19 patients had higher all-cause mortality than Influenza patients in all age groups ≥41 years.
- Influenza patients had higher readmission rates and increased mortality among younger survivors (41-64 years) compared to COVID-19 patients.
- Hospitalization duration was longer for patients with COVID-19 compared to those with Influenza.

## Abstract

Large-scale registry-based studies on patients hospitalized with COVID-19 as compared to Influenza are scant, yet they are needed to re-evaluate the pandemic and the characteristics of patients at risk of severe outcomes.

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 the four age groups (19–40, 41–64, 65–74, and ≥75 years).

Hospitalized COVID-19 and Influenza patients had a larger medication load as compared to the general population. Across all investigated age groups, polypharmacy was more frequent in the Influenza group. The risk for all-cause death in the entire follow-up period and death during hospital stay was higher in the COVID-19 group as compared to the Influenza group for all age groups ≥41 years. Furthermore, the duration of hospitalization was longer in patients with COVID-19. 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.

In the first 2 years of the pandemic, COVID-19 had devastating effects on 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.