Methods for health economic evaluations of vaccines-results from an international expert-workshop

Objectives: Health economic evaluations (HEEs) of vaccines are commonly considered during immunization introduction decision-making processes in most industrialized countries. Despite the availability of guidelines advocating more standardization for such HEEs, there are still several infection/immunization-specific particularities that are debated in the scientific community. An international expert-workshop was convened to identify good practices for (i) how to conduct HEEs of vaccines and (ii) how to consider results of HEE in vaccine introduction decision-making. Methods: A systematic literature search was conducted to identify prevailing opinions and remaining issues of HEE in vaccination. Twentytwo experts in the field of health economics and immunization decision-making were invited to a workshop and were asked to answer a survey-questionnaire based on the systematic literature search beforehand to inform the preparation of group work sessions (GWS). In GWS, issues focusing on 'mathematical modeling', 'health economics', and 'decision-making' were discussed and summarized. Results: The GWS (based on systematic literature search) included topics such as cost-components, quality of life (QoL), discounting, and perspectives leading to suggestions such as including caregiver QoL impact and applying decreasing time-related discount rates. Since vaccination often causes indirect effects, the use of dynamic models is required and exceptions should be justified. In order to facilitate transparent decision-making, the results of HEE should present parameter and methodological uncertainty as well as cumulative and time-specific figures. The majority of countries in Europe use results from HEEs in an informal judgment-process without willingness to pay (WTP) threshold. The expert-group emphasized that transparency should be maximized in decisionmaking process. Conclusions: The deliberations led to suggestions on several HEE issues. However, vaccines not always need to be considered differently in HEE since other interventions might share similar characteristics. Transparency in the conduct and presentation of HEE, and subsequent decision-making is essential, especially in the absence of explicit WTP thresholds.