Economic evaluation of vaccines: specificities and future challenges illustrated by recent European examples

This study reviews the current challenges in the economic evaluation of vaccines with a focus on European countries. In particular, the type of clinical evidence generally available, the impact of discounting for time preference and the use of modeling to derive valid cost-effectiveness assessments are considered. First, the characteristics of evidence for vaccines are discussed, as well as potential difficulties faced when using evidence-based medicine applied to curative drugs to interpret vaccine evidence. Then, discounting is considered and specific examples illustrating issues with different types of discounting are described, taking HPV as the example. Finally, the need for sometimes complex dynamic models for vaccines is explored, and specific types of models are reviewed, keeping into consideration the adage "complex when needed, straightforward if allowed."