Recently in this journal, O'Mahony and colleagues [1] published an article on the practical implications of differential discounting in the analysis of the cost-effectiveness of human papillomavirus (HPV) vaccination in the Netherlands. In particular, they show a fall in the cost-effectiveness ratio with the inclusion of additional cohorts under differential discounting. We disagree with some arguments and suggestions made by the authors and will list these below with adjacent argumentation. We start with briefly summarizing the state of the art on discounting in health economics and for vaccines' health economics in particular.

In general, in health economics, discounting of health outcomes has been heavily debated already for various decades. The practical consensus often is to discount health outcomes with an equal rate compared with that of costs. However, it has been argued that health effects should be discounted with a lower rate than costs, given the expected increase in the value of health over time. Furthermore, differences in the pace at which economies and life expectancies grow pose an argument for differential discounting. These arguments have been substantiated with specific methodological frameworks [2,3]. However, consensus on differential discounting certainly does not yet exist [4,5], and currently only in the Netherlands and Belgium differential discount rates are used for future costs and health outcomes (in particular, 3–4% for costs and 1.5% for health effects). Cost-effectiveness analyses in the Netherlands that have contributed to health-care policy decisions recently have consistently used these specific percentages for discounting, including those analyses that were directed at the cost-effectiveness of HPV vaccination [6]. In the area of vaccines, discounting impacts relatively strong as compared with, for example, classical pharmaceuticals [7]. Previously, we have advocated differential discounting in particular for HPV vaccination [8,9].