Objectives: An analysis was conducted in Japan to determine the most cost-effective neuraminidase inhibitor for the treatment of influenza virus infections from the healthcare payer’s standpoint.

Methods: This study reanalyzed the findings of a previous study that had some limitations (no probabilistic sensitivity analysis, quality of life scores measured by the EQ-5D-3L instead of the EQ-5D-5L, and the use of a decision tree model with only three health conditions) by using data from a network meta-analysis study. A decision tree model with eight health conditions was constructed, and costs were identified as medical costs and drug prices (the 2020 version of the Japanese medical fee index). The effectiveness outcomes were measured using EQ-5D-5L questionnaires for adult patients who had previously experienced influenza virus infections. The time horizon was 14 days. Both deterministic and probabilistic sensitivity analyses were performed to examine the robustness of the results.

Results: The base-case cost-effectiveness analysis revealed that oseltamivir outperformed laninamivir, zanamivir, and peramivir, making it the most cost-effective neuraminidase inhibitor. The deterministic and probabilistic sensitivity analyses showed robust results that validated oseltamivir as the most cost-effective among the four neuraminidase inhibitors.

Conclusions: This study thus reconfirmed oseltamivir’s position as the most cost-effective neuraminidase inhibitor for the treatment of influenza virus infections in Japan from the standpoint of healthcare payment. These findings can help decision-makers and healthcare providers in Japan, including pharmacists, create and manage formularies.