Cost-effectiveness of quadrivalent versus trivalent influenza vaccine in the United States

BACKGROUND: Currently used trivalent influenza vaccines (TIVs) contain two strains of influenza A and one strain of influenza B. However, co-circulation of two distinct B lineages and difficulties in predicting which lineage will predominate in the next season have led to frequent B-strain mismatches. Newly registered quadrivalent influenza vaccines (QIVs) include two B strains and might therefore provide wider protection. Objectives: To evaluate the cost-effectiveness of using QIV versus TIV for routine influenza vaccination in the United States (US) during the next 20 years. Methods: A dynamic transmission model was used to estimate the additional protection offered by QIV over TIV against symptomatic influenza B disease. Subsequently, we used a decision tree model to determine the costeffectiveness of replacing TIV with QIV from a societal perspective. US data on influenza-related disease outcomes and corresponding costs were derived from published sources (e. g. Molinari et al. 2007). Results: Over 20 years, replacing TIV with QIV is predicted to prevent 13.3 million influenza B cases. According to our model this resulted in a reduction of 113,000 hospitalizations and 13,200 deaths. Moreover, 200,000 quality- adjusted life-years (QALYs), US$3.1 billion in medical costs and US$0.6 billion in indirect costs were saved. The base case estimate of the incremental cost-effectiveness ratio (ICER) was US$29,000 per QALY gained. Economic parameters with highest impact on the ICER were vaccine price, QALY loss due to influenza and probability of hospitalization or death given symptomatic infection. Conclusions: Introducing QIV into the immunization program of the United States would prevent a substantial number of hospitalizations and deaths. Moreover, cost-effectiveness was shown to be favorable when a cost-effectiveness threshold of US$50,000 is applied