Cost-effectiveness and public health impact of using high dose influenza vaccine in the Japanese older adults.

Background: High-dose (HD) influenza vaccine, which has demonstrated superior efficacy and acceptable safety compared to standard-dose (SD), has market authorization in many countries. This study evaluated the public-health impact and cost-effectiveness of HD versus SD in Japanese older-adults (OAs) from healthcare payer-perspective.

Methods: Decision-tree model was employed assessing health outcomes for each vaccination strategy, simulating influenza cases, outpatient/emergency department (ED) visits, hospitalizations, and mortality, over one-year time-horizon. Incremental cost-effectiveness ratios (ICER) were assessed at Japanese willingness-to-pay (WTP) threshold. Base-case analysis considered influenza vaccines effective against influenza hospitalizations only, whereas complementary analyses reflected their efficacies against Pneumonia and Influenza (P&I), respiratory and cardiorespiratory hospitalizations possibly related to influenza among individuals ≥65 years. Scenario analysis extended target population to at-risk individuals aged 60-64 years. Uncertainty was assessed using sensitivity analyses.

Results: In base-case, switching from SD to HD prevented 174,863 influenza cases, 121,084 outpatient and 614 ED visits, annually. Further, 5,777 influenza hospitalizations, and 2,406 deaths related to influenza were avoided with HD vaccine. The HD vaccine was found to be a cost-effective strategy at WTP threshold of ¥5,000,000/Quality-Adjusted-Life-Years (QALY) with ICER of ¥4,876,512/(QALY). Sensitivity analyses confirmed the robustness of these findings. Complementary analyses showed notably improved outcomes, in terms of public-health, economic impact, and ICERs, when considering efficacy of influenza vaccines against P&I, respiratory, and cardiorespiratory hospitalizations possibly related to influenza.

Conclusion: These results indicate that HD vaccine has a high economic value in Japan compared to SD. Implementing HD vaccine could effectively alleviate the burden on healthcare facilities for Japanese OAs.