COVID-19 case fatality rate and infection fatality rate from 2020 to 2023: Nationwide analysis in Austria

• DOI: 10.1016/j.jiph.2025.102698
• Publication Date: 2025-02-10T17:15:38Z
• Authors: Uwe Riedmann; Alena Chalupka; Lukas Richter; Martin Sprenger; Wolfgang Rauch; Robert Krause; Peter Willeit; Harald Schennach; Bernhard Benka; Dirk Werber; Tracy Beth Høeg; John PA Ioannidis; Stefan Pilz
• Keywords: Male; Adult; Case fatality rate; COVID-19/mortality; Adolescent; SARS-CoV-2; Nursing Homes/statistics & numerical data; COVID-19; Infectious and parasitic diseases; RC109-216; Middle Aged; Infection fatality rate; Young Adult; Nationwide; Austria; 80 and over; Humans; Female; Austria/epidemiology; Public aspects of medicine; RA1-1270; Aged; Retrospective Studies

Background: Comprehensive analyses of COVID-19 case fatality rates (CFRs) and infection fatality rates (IFRs) that span the entire pandemic are not yet available but critical to retrospectively evaluate the COVID-19 disease burden and its related public health policies. We used nationwide individual participant data from Austria, the continental country with the highest SARS-CoV-2 testing rate per capita, to calculate COVID-19 CFR and estimate IFR covering the entire pandemic. Methods: This retrospective observational study included all Austrian residents and covered the time from February 2020 to May 2023, examining CFRs overall, monthly, and during dominant SARS-CoV-2 variant periods. CFRs were calculated for the whole population and stratified according to immunization status (presence of previous vaccination and/or infection), age, gender and nursing home residency. We additionally estimated the IFRs based on estimations of undocumented infections using a test positivity model. Results: The overall CFR of 30-day COVID-19 mortality was 0.31 % but varied depending on month, with the highest being 5.9 % in April 2020 and the lowest 0.07 % in January 2022. The variant periods reflected this trend of decreasing CFR, with the highest for Wuhan-Hu-1 (2.05 %) and the lowest for BA.1 (0.08 %). Overall CFRs were particularly high in the group without any previous immunizing event (0.67 %), the elderly (85 + year group: 7.88 %) and in nursing home residents (7.92 %). Nursing home residents accounted for 30.82 % of all COVID-19 deaths while representing only 1.22 % of diagnosed infections. Total SARS-CoV-2 infections were estimated to be almost double than confirmed cases with a corresponding overall IFR of 0.16 %. Conclusion: This estimation of nationwide CFR and IFR across the entirety of the SARS-CoV-2 pandemic gives crucial insights into the period-dependent variability of the severity of diagnosed COVID-19 cases and its risk factors. Our findings further underline the disproportionate severity of COVID-19 among the elderly and especially nursing home residents.