Multi-model analysis to quantify the impact of vaccination on COVID-19 and influenza hospitalisation burden among older adults in the EU/EEA, 2024/25
Influenza vaccine coverage remains below the World Health Organization (WHO)-recommended threshold for risk groups in most EU/EEA countries, while COVID-19 vaccine coverage is declining across most countries. Despite the role that vaccines play in reducing severe disease, a comprehensive EU/EEA-wide quantification and assessment of the impact of influenza and COVID-19 vaccination programmes on hospitalisations is currently lacking.
To address this, we quantified the expected impact of vaccination programmes using a collaborative modelling approach through RespiCompass, the European respiratory diseases scenario modelling hub. This hub coordinated the development of multiple mechanistic disease transmission models by international modelling teams to simulate scenarios designed to assess vaccination impact. This assessment provides evidence to inform national public health institutes, vaccination programme managers, healthcare professionals, science communicators and public health advocates.
Our analysis suggests a clear reduction in influenza and COVID-19 hospitalisations due to vaccination in the EU/EEA between 5 August 2024 and 1 June 2025. This reduction varies strongly between countries with different vaccine coverage levels. For individuals 65 years old and above, influenza vaccination was projected to prevent – on average across EU/EEA countries – between 26% and 41% of influenza-related hospitalisations over the 2024/25 epidemiological season, depending on assumed country-specific vaccine coverage and viral transmissibility. For COVID-19, the projected reduction in hospitalisations for individuals 65 years old and above was between 14% and 20% across EU/EEA countries, depending on assumed country-specific vaccine coverage and assumptions related to waning immunity.
A large heterogeneity across countries was observed for the impact of vaccination on both diseases, reflecting differences in vaccine coverage. Depending on the modelled scenario, the difference in averted hospitalisations between the country with highest versus lowest averted burden was between 48 and 70 percentage points for influenza, and between 37 and 54 percentage points for COVID-19.
This inter-country variation highlights the untapped potential to reduce hospital burden in the EU/EEA through established programmes, such as seasonal influenza vaccination, as well as newer interventions like COVID-19 vaccination. At a time when a number of EU/EEA countries are assessing routine immunisation schedules for COVID-19, these findings can underpin national and subnational cost-effectiveness calculations to guide resource allocation for vaccination campaigns and support messaging efforts.
