IS HIGH-DOSE INFLUENZA VACCINE COST-EFFECTIVE IN HIGH-RISK NONELDERLY PATIENTS?

Purpose: High-dose influenza vaccine has been shown to improve protection of the elderly, in whom standard-dose vaccines are less effective. Evidence suggests that younger adults with conditions that increase influenza risk may have similar suboptimal responses to standard-dose vaccine and could benefit from high-dose vaccine. The cost-effectiveness of high-dose influenza vaccine in nonelderly populations is unclear.

Method: We performed a Markov model-based cost-effectiveness analysis, comparing 5 influenza vaccination strategies in 50-64 year-olds: no vaccination, all receiving trivalent influenza vaccine (All TIV), all receiving quadrivalent vaccine (All QIV), high-risk patients receiving high-dose TIV/others receiving TIV, and high-risk patients receiving high-dose TIV/others QIV. Effectiveness estimates for high-dose vaccine among high-risk adults 50-64 years was extrapolated from data in the elderly, and estimates of standard-dose TIV/QID effectiveness in high-risk patients were varied widely in sensitivity analyses. Other model parameter values were obtained from US databases and the medical literature. A single influenza season was modeled, with effectiveness measured as quality adjusted life year (QALY) losses avoided due to vaccination. QALY losses due to influenza mortality were discounted at 3%/yr. Robustness of model results were tested in sensitivity analyses.

Results: At baseline, compared to no vaccination, All TIV cost $28,800/QALY gained. Compared to All TIV, All QIV cost $59,900/QALY gained, and compared to All QIV, high-dose TIV in high-risk patients and QIV in the remainder cost $84,900/QALY gained. The high-dose TIV for high-risk/TIV in others strategy was dominated. Results were sensitive to variation of 3 uncertain parameters: standard-dose vaccine and high-dose vaccine effectiveness in high-risk patients, and standard-dose vaccine effectiveness in the entire population (which has been highly variable in recent influenza seasons). Varying these 3 parameters simultaneously, using a $100,000/QALY threshold (Figure) showed that, if high-dose vaccine relative effectiveness in high-risk patients increases by ≤0.18 (base case 0.242), high-dose in high-risk/usual dose in others was not favored. Results were also sensitive to variation of influenza incidence parameters and vaccine cost.

Conclusion: Whether high-dose influenza vaccine in high-risk nonelderly patients is economically reasonable largely depends on assumptions regarding uncertain parameter values; thus, its cost-effectiveness in this group remains unclear. Further research is needed regarding protection from influenza afforded by available vaccines in nonelderly high-risk groups.