Cost-Effectiveness Analysis of Oseltamivir for Influenza Treatment Considering the Virus Emerging Resistant to the Drug in Japan

Aim:  The purpose of this study is to evaluate the cost-effectiveness of oseltamivir for influenza in Japan considering the complications and the emergence of oseltamivir-resistant virus.
Methods:  Study design is a cost-effectiveness analysis in decision analytic modeling based on previously published evidence. Outcome measures included costs and quality-adjusted life year (QALY).
Results and Conclusion:  In the base-case analysis, the incremental cost-effectiveness ratio (ICER) of oseltamivir during influenza and complications was JPY398,571 ($3320) per QALY without productivity loss, which implied oseltamivir is evidently cost-effective. Furthermore, considering the productivity loss, the ICER for oseltamivir turned to be negative, which means simply dominant. When the prevalence was in the low range of 10% to 38%, oseltamivir became less cost-effective than conventional treatment. Regarding potential emergence of the drug-resistant virus, we found the dominance of oseltamivir will vanish if the emerging rate becomes larger than 27%. The two-way sensitivity analysis also suggested that if the resistant virus rate becomes less and the prevalence higher, then oseltamivir becomes more advantageous. The analysis for uncertainty, using cost-effectiveness acceptability curve by Monte Carlo simulation, resulted in the estimate of about 80% chance that oseltamivir could be cost-effective at the willingness-to-pay level of JPY6,000,000 ($50,000), which is commonly accepted as an affordable threshold.