OBJECTIVES: Quadrivalent influenza vaccine (QIV), containing both B-lineage strains, is expected to demonstrate superior effectiveness when the circulating B strain does not correspond to the one contained in trivalent influenza vaccine (TIV). Economic evaluation of replacing TIV by QIV in Turkey is crucial for public payers. This study examined the incremental cost-utility ratio of QIV vs. TIV from a payer and societal perspective and key assumptions that influence the study results.

METHODS: We used a static cohort model that incorporated costs, health outcomes, and quality-adjusted life-year (QALY) losses associated with influenza to evaluate QIV and TIV for the currently reimbursed cohort during an average influenza season in Turkey. Epidemiological data were based on surveillance figures; demographics and proportion of people at-risk were extracted from the Turkish census and the national household health survey; and cost data were estimated from national price lists, cost-of-illness studies and assumptions when data were not available. One year time horizon and a discount rate of 3% were used.

RESULTS: Using QIV instead of TIV in Turkey would avoid an additional 15,092 influenza cases, 6,311 outpatient consultations, 94 hospitalizations and 13 deaths. The incremental cost per QALY gained when using QIV over TIV would be 77,932 TRY from a payer perspective and 73,953 TRY from a societal perspective. The cost-utility ratio was the lowest among subjects over 65 years old (48,869 TRY per QALY gained). Cost-utility ratios were sensitive to assumptions used for vaccine effectiveness, level of mismatch, and cost of QIV.

CONCLUSIONS:

Vaccinating the current reimbursed cohort with QIV instead of TIV is economically efficient in Turkey using a threshold of 3x Gross Domestic Product Per Capita. Uncertainty in the epidemiological patterns of influenza, vaccine effectiveness, and level of mismatch are key factors to consider.