OBJECTIVES: Antiviral drugs are recommended and widely used for the treatment of influenza in Japan. The aim of this study was to investigate cost-effectiveness of baloxavir marboxil (baloxavir) versus laninamivir, the most widely used antiviral for influenza in Japan, in otherwise healthy adult patients conditional on result of rapid influenza diagnostic test.

METHODS: A decision tree was used to describe the course of influenza and predict associated costs and quality-adjusted life-years (QALYs) over one year, by antiviral. Costs were valued from the public healthcare payer’s perspective, including influenza test, antiviral acquisition, other medications, physician visits, any other outpatients costs associated with influenza or adverse events, and hospitalisations. Resource utilisation and unit costs were obtained from an analysis of the JammNet claims database and adjusted to year 2018. Health state utilities were driven by influenza symptoms, drug-related adverse events (DRAEs), and complications caused by influenza. They were obtained from the clinical trial of baloxavir using EQ-5D-5L and a previous UK model commissioned by NICE. Deterministic and probabilistic sensitivity analyses (DSA/PSA) were performed. A willingness-to–pay threshold of ¥5,000,000/QALY was considered.

RESULTS: The estimated total costs per patient were ¥9,393 and ¥9,130 for baloxavir and laninamivir respectively. The additional acquisition cost of baloxavir was partly offset by adverse event costs avoided. The incremental cost/QALY gained for baloxavir versus laninamivir was ¥2,336,603, which is below the considered willingness-to-pay threshold. The main influential factors of the model results were probability of DRAEs and duration of influenza symptoms for laninamivir based on the results of DSA. The PSA showed a probability of 65% that baloxavir is cost-effective versus laninamivir.

CONCLUSIONS: This model suggests that treating influenza with baloxavir would be cost-effective compared to laninamivir in otherwise healthy adult patients in Japan. Further evaluations are needed in different settings such as high-risk population.