Economic evaluation of influenza vaccination and economic modelling. Can results be pooled?

Scientific reviewing methods were applied to economic studies of influenza vaccination, and an economic model of influenza vaccination was developed from these primary sources. Issues arising from the secondary literature review include the quality of evidence on the effectiveness of the vaccines, the absence of a traditional population-based approach to reviewing economic data, confusion in terminology, and how to generalise from resource data contained in primary evaluations. Data from the literature review were summarised in terms of resource units used in the prevention and treatment of influenza. An economic model was constructed using local unit costs (from the Emilia region of Italy) and applying the data to a notional population. The model was sensitive to length of stay in hospital but not to variation in incidence of influenza, days off work or number of medical consultations. The model was predicated on and is sensitive to an estimate of 80% vaccine effectiveness. The approach is constrained by the available data, but could be more generally useful in that it allows variations in the quantity of inputs to be considered separately from variations in their values. The model may be used locally as a decision-making tool, although the method needs further development.