Measuring the Vaccine Success Index: A Framework for Long-Term Economic Evaluation and Monitoring about the Case of Rotavirus Vaccination

New vaccination programs need a method to measure success based on pre-defined outcomes evaluated over pre-specified time frames. Reimbursement of newly approved vaccines is often reliant on simulated projections that approximate real-world scenarios, due to limited long-term data availability. Adjustments to reimbursement prices are infrequent, barring instances of market competition-induced price erosion through tender processes. Consequently, comprehensive monitoring of the vaccine effect (VE) for an adequate duration to evaluate the success of vaccination programs remains rare. Such data are essential to inform expectations of vaccine effect and the timeline for measurable success of the investment. An example is provided here by the 15-year assessment of the rotavirus vaccination program in Belgium (RotaBIS study spanning 2005 to 2019 across 11 hospitals). The vaccination program started in late 2006 and yielded sub-optimal outcomes. Long-term VE surveillance data provided insights into infection dynamics, disease progression, and vaccine performance. The presented analysis introduces novel conceptual frameworks and methodologies. Cost-effectiveness analysis (CEA) evaluates the initial target vaccination population, considering the effectiveness of direct and indirect effects of the vaccine, compared with a historical group that is unvaccinated. Cost-impact analysis (CIA) covers a longer period and considers the whole vaccinated and unvaccinated population in which the vaccine has direct and indirect effects. The success index ratio of CIA over CEA outcomes evaluates the vaccination performance. Good performance has ≤ 1 index value combined with a low CEA. This measure is therefore a valuable aid for new vaccine introductions. It supports the establishment of robust monitoring protocols.