OBJECTIVES: Influenza infections epidemics are responsible for medical and social concerns because they are associated with considerable morbidity and mortality in Japan. Neuraminidase inhibitors (NI) appear to be an effective treatment strategy. The study aimed to compare the relative costs and outcomes among four NI strategies for initiation of influenza treatment in adult-outpatient settings from a healthcare payer’s perspective.

METHODS: Using a CEA model, we compared four different NI drugs including oseltamivir, zanamivir, laninamivir, and peramivir. Costs included medical costs and pharmaceutical charges. Medical costs were obtained from the institutional medical fee scheduled table 2016. Authorized medication costs were applied to this study. Outcomes of effectiveness were measured using EQ-5D questionnaires that were applied to patients with influenza virus infections. The study time-horizon was defined as 14 days.

RESULTS: Cost Effectiveness Ratios for oseltamivir, zanamivir, laninamivir, and peramivir were 341,076 (Yen/QALY), 351,818, 356,780, and 343,419, respectively. The CEA base-case analysis showed oseltamivir was the most cost-effective in NIs. Zanamivir and laninamivir were dominated. Incremental Cost Effectiveness Ratio (ICER) was 396,043 (Yen/QALY). One-way sensitivity analyses were performed in terms of “duration of treatment”, “QOL values”, “costs of pharmaceutical charges” (+-10%), “costs of physician visits” (+-10%), “costs of community pharmacy visits” (+-10%), “costs of hospital admission” (+-10%), and “effectiveness to high risk patients” (effective 92.9% and pneumonia 8.1%). The maximum ICER in terms of “effectiveness to high risk patients” was 1,352,104 (Yen/QALY) less than 5,000,000 (Yen/QALY).

CONCLUSIONS: The study results show that oseltamivir was the most cost-effective NI drug for the treatment of influenza virus infection in adult-outpatient settings. Our findings can provide decision-makers with scientific evidence of clinical and economic evaluation for optimal therapeutic outcomes.