Evaluating the cost-effectiveness of adjuvanted influenza vaccine in the older adult population in the Netherlands

In the Netherlands, older adults are vaccinated with the standard (dose) influenza vaccine (sIV). Enhanced vaccines, such as the adjuvanted influenza vaccine (aIV) and high-dose (HD-IV) influenza vaccine, have demonstrated clinical and economic benefits. This analysis aimed to evaluate the cost-effectiveness of replacing sIV by aIV in adults aged 60y and older and in high‑risk adults aged 50-59y in the Netherlands. A static decision-tree model was adapted to the Dutch setting to assess the associated costs and health outcomes. The model simulated a historic single average influenza season during 2013-2020 from a societal perspective. Influenza-specific data were used to estimate symptomatic incidence, general practitioner (GP) visits, hospitalizations and excess mortality. Recent publications on aIV's effectiveness that met the inclusion criteria provided a set of non-randomized real-world data. These studies provided a relative vaccine effectiveness (rVE) range that approximated the 10-30% rVE reported by the Dutch Health Council in a recent assessment; this range was analyzed in the economic model. Sensitivity analyses assessed uncertainty, including varying the rVE over a broader range. Applying an rVE range of 10-30%, ~1,571-4,713 GP visits, 498-1,494 hospitalizations, and 347-1,041 deaths could have been avoided. These health benefits translated into €4.3-12.8 million cost savings and 2,220-6,659 quality-adjusted life years (QALYs) gained. The incremental cost-effectiveness ratio (ICER) was estimated at €2,144-11,903/QALY. Based on economic modeling, replacing sIV with aIV is suggested to be a cost-effective strategy, with ICERs below the commonly accepted willingness-to-pay threshold of €50,000/QALY gained.