Estimating the Clinical and Economic Impact of Introducing an RSV Vaccination Campaign in Older Adults in Lombardy

Respiratory Syncytial Virus (RSV) is a major cause of respiratory illness and hospitalization among older adults. With the recent introduction of RSV vaccines for the elderly population, evaluating their potential epidemiological and economic impact has become increasingly relevant for public health planning. This study develops a data-driven modeling framework to assess the potential impact of RSV vaccination among individuals aged 65 and older in Lombardy, Italy. The approach combines epidemiological estimation, vaccination uptake scenarios, and health economic evaluation. First, baseline weekly RSV incidence in the 65+ population is estimated using historical surveillance data. Second, future vaccination uptake is simulated through logistic adoption models calibrated on historical influenza vaccination trends in the elderly population. Three scenarios (low, medium, and high uptake) are defined to represent different vaccination coverage trajectories. Future RSV incidence patterns are simulated using recent seasonal dynamics combined with stochastic variation in intensity and timing. These trajectories are then integrated with vaccination coverage to estimate reductions in RSV-related hospitalizations and deaths. A cost analysis compares vaccination program costs with savings from avoided hospitalizations. Results suggest that RSV vaccination could substantially reduce severe disease burden among older adults, although the economic impact depends strongly on vaccine price and vaccination coverage. The proposed framework provides a flexible tool for evaluating vaccination strategies and supporting public health decision-making in aging populations.