Cost-effectiveness analysis of influenza vaccination with a high-dose vaccine versus an adjuvanted quadrivalent vaccine in older adults in Spain

ABSTRACT Objectives Influenza is a widespread acute respiratory illness posing a major public health challenge for both the National Health Service (NHS) and society, particularly among older adults. This study aimed to assess the cost-effectiveness of high-dose quadrivalent vaccine (HD-QIV) versus adjuvanted quadrivalent vaccine (aQIV) in older adults in Spain. Methods Public health and economic benefits were evaluated using a decision-tree model considering influenza cases, GP and ED visits, hospitalizations, and influenza-related mortality. Deterministic and probabilistic sensitivity analyses addressed epidemiological and economic uncertainties. Results From a societal perspective, HD-QIV prevented 54,039 influenza cases, 7,733 GP consultations, 1,585 ED visits, 27,398 episodes of hospitalization due to cardiorespiratory events over a single influenza season and 1,203 deaths compared to aQIV when vaccinating adults ≥65 years old in Spain, resulting in 14,316 LYs and 12,440 QALYs gained over a lifetime horizon. The reduction in health outcomes outweighed the increase in vaccination costs, translating to a reduction in total costs with HD-QIV compared to aQIV. Therefore, vaccinating older adults in Spain with HD-QIV instead of aQIV was a dominant strategy when evaluating hospitalizations due to respiratory and cardiovascular events. HD-QIV remained dominant from a NHS perspective. Sensitivity analyses confirmed the robustness of the model. Conclusions This analysis showed that vaccinating older adults in Spain with HD-QIV instead of aQIV would reduce influenza cases, GP and ED visits, hospitalizations, deaths, and associated costs, and thus it should be the strategy of choice in a situation of budgetary constraints from either a societal or an NHS perspective. HIGHLIGHTS A decision-tree cost-effectiveness model addressed the evidence gap of lacking head-to-head trials between HD-QIV and aQIV in older adults, using the highest available evidence and indirect comparison via SD-QIV. HD-QIV prevented more influenza cases, hospitalizations, and deaths than aQIV, resulting in greater life-years and QALYs gained, and substantial cost savings for both society and the NHS. These findings support HD-QIV as the preferred vaccination strategy for older adults in Spain, providing robust evidence for policymakers to optimize influenza prevention and healthcare resource allocation.