Nationwide estimates of SARS-CoV-2 infection fatality rates and numbers needed to vaccinate for SARS-CoV-2 vaccines in 2024 in Austria

Background: Post-pandemic years are characterized by widespread previous population immunisation against COVID-19. Whether and for whom SARS-CoV-2 vaccinations are still justified is unclear. We use nationwide estimates of IFR and literature derived estimates of vaccine effectiveness (VE) to calculate numbers needed to vaccinate to prevent one COVID-19 death (NNV) and for one life-year saved (LYS) in Austria in 2024. Methods: In this retrospective analysis we calculate SARS-CoV-2 IFR during 2024 in Austria according to previously published wastewater-based infection estimates and available mortality data. Using literature derived VE estimates we calculate NNV to prevent one COVID-19 death and for one LYS in strata according to age groups, nursing home residency and vaccination in 2024. We repeat analyses with sensitivity range values of parameters. Results: In 2024, total IFR was 0.048%. NNV (LYS) in the age groups 0-19, 20-39, 40-59, 60-74 and 75-84 years were very high: e.g. 5,497,526 (151,570), 2,432,498 (92,614), 415,714 (24,777), 35,925 (3,748), and 4,882 (1,009), respectively, in community dwellers. In the 85+ years age group, IFRs of unvaccinated/vaccinated were 0.91%/0.77% for community dwellers, and 1.22%/1.04% for nursing home residents. The 85+ year age group had NNV estimates of 1,215 and 907 (LYS: 525 and 1,896) in community dweller and nursing home residents, respectively. Sensitivity analyses yielded LYS<1,000 only under some favourable assumptions in the 75-84 and 85+ years old age strata. Conclusions: In 2024 SARS-CoV-2 IFR was low and NNV and LYS of COVID-19 vaccinations correspondingly non-favourably high, even for very old individuals.