Cost effectiveness of zanamivir for the treatment of influenza in a high risk population in Australia

Objective: To use data from a clinical trial of zanamivir, a new antiviral drug, to estimate the costs and effectiveness of alternative treatment stra tegies for a highrisk population in Australia visiting a physician for trea tment of influenza or influenza-like illness within 36 hours of symptom ons et. Design and setting: This was a modelling study using data from a randomised , double-blind, placebo-controlled trial with centres in Australia, New Zea land and South Africa. Cost data were taken from standard Australian source s. Methods: Efficacy data from the clinical trial were used to populate a comp uter model designed to estimate the costs and health outcomes associated wi th alternative treatments for influenza and influenza-like illness. Only pa tients who consulted the physician within 36 hours of symptom onset were in cluded in this trial. Cost data were used to translate the clinical data in to treatment cost estimates. Results: Treatment with zanamivir for this high risk population results in an incremental cost of $A14.20 per day of symptoms avoided in the base case . The cost per quality-adjusted life-year (QALY) gained is $A11 715. The re sults are sensitive to several parameter values, including the influenza-po sitive rate and the impact of zanamivir on days to alleviate symptoms and h ospitalisation. Conclusions: Influenza is costly for the high risk population who seek phys ician treatment. Treatment with zanamivir for this population is cost effec tive based on an $A78 000 per QALY benchmark. Zanamivir could be cost savin g if it reduces the hospitalisation rate.