On-going assessment of coronavirus disease 2019 (COVID-19) vaccine impact on disease outcome rates is important to inform recommendations for COVID-19 vaccination programs. We aimed to summarise earlier estimates and present new data (from December 2024 to May 2025) on vaccine effectiveness. We used Australian census data linked to a national immunisation register and death registrations to track COVID-19 vaccine effectiveness in preventing COVID-19-specific mortality among an open cohort of 4 million adults aged 65 years and older during 7 periods between 2022 to 2025 corresponding to different SARS-CoV-2 Omicron subvariant circulation and variant-specific vaccine formulations. We compared COVID-19 mortality rates with survival analysis, adjusting for age and other characteristics. We show that in January to May 2022, ancestral COVID-19 vaccine effectiveness was 93.5% (95%CI 92.6-94.2%); COVID-19 mortality rates in unvaccinated versus recently vaccine boosted individuals (within last 3 months) were 929 versus 61 per 100,000 person-years. By December 2024 to May 2025, JN.1-variant COVID-19 relative vaccine effectiveness (compared to individuals whose last COVID-19 vaccine was more than 1 year ago) was 47.7% (95%CI 15.4-67.7%); COVID-19 mortality rates in unvaccinated, vaccinated more than 1 year ago and JN.1 booster recipients were 51, 31 and 16 per 100,000 person-years respectively. COVID-19 vaccination significantly reduces COVID-19 mortality in older adults. While the absolute mortality reduction from vaccination is less in 2025 than 2022, vaccination of older adults still confers a significant mortality benefit.
Liu et al. (Fri,) studied this question.