Cost-effectiveness analysis of inhaled zanamivir in the treatment of influenza A and B in high-risk patients.

OBJECTIVE: To evaluate the cost effectiveness of zanamivir 10 mg twice daily for 5 days in the treatment of influenza in high-risk patients.
DESIGN: Bootstrap cost-effectiveness analysis incorporating within-trial analysis of pooled patient-level cost and effect data.
SETTING: UK unit costs and utilities applied to high-risk patients drawn from 6 multinational clinical trials. PATIENTS: A total of 154 zanamivir and 167 placebo high-risk patients were included in the analysis. MAIN OUTCOME MEASURES: Cost per day of normal activities; cost per symptom-free day; cost per complication averted; cost per quality-adjusted life-year (QALY).
RESULTS: The mean benefit was estimated to be 2.5 days [95% confidence interval (CI): 0.68 to 4.27] of normal activities gained; 2.0 (95% CI: 0.56 to 3.51) symptom-free days; and a 9% reduction in complications (95% CI: 0 to 18%). Excluding the effect of rare hospitalisation costs, the cost (1999 values) of gaining a day of normal activities was 9.50 Pounds (95% CI: 5 Pounds to 39 Pounds); cost per symptom-free day was 11.56 Pounds (95% CI: 6 Pounds to 43 Pounds); cost per complication averted was 262 Pounds (95% CI: 90 Pounds to 1574 Pounds). Influenza was estimated to reduce utility by 0.883 per day, demonstrating the debilitating effect of the disease. Extrapolating a day of normal activities to a standard utility measure resulted in a cost per QALY of 3900 Pounds excluding inpatient costs (7490 Pounds including inpatient costs). Cost-effectiveness acceptability curves demonstrated 90% certainty that zanamivir would be cost effective at 8000 Pounds per QALY.
CONCLUSIONS: Significant health benefits can be obtained with zanamivir treatment in high-risk patients. The cost per QALY for zanamivir in these patients compares well with that of other commonly used pharmacological interventions.