Effect of oseltamivir on the risk of pneumonia and use of health care services in children with clinically diagnosed influenza

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Abstract
Objective: To evaluate the effectiveness of oseltamivir in reducing the rate of complications of influenza in children. Research design and methods: Anonymous, patient-level data from Medstat's MarketScan Research Database between 2000 and 2004 were used to identify children with influenza, aged 1–12 years. Patients who received a prescription for oseltamivir within 1 day of influenza diagnosis were compared with those who received no antiviral therapy. Main outcome measures: Primary and secondary study outcomes included occurrence of pneumonia within 14 days of onset of influenza, rates of hospitalization for pneumonia, antibiotic use, numbers of healthcare services utilized, and healthcare expenditures. Results: In total, 4447 (17.9%) children received a prescription for oseltamivir within 1 day of when they were first clinically diagnosed with influenza, and 20 407 (82.1%) children received no antiviral treatment. Overall, children who received oseltamivir for the treatment of physician-diagnosed influenza were 51.7% less likely to be clinically diagnosed with pneumonia at a subsequent medical encounter (relative risk 0.483; 95% CI: 0.326, 0.717). This benefit was associated with reductions in antibiotic use, outpatient and emergency room visits, and savings in outpatient medical expenditures. Net expenditures per patient were not significantly different between children receiving oseltamivir and those who received no antiviral treatment (–$16; 95% CI: –$13, +$40) although pharmacy expenditures were higher. Wide regional variations in oseltamivir use were noted. Limitations: The study was restricted to patients with employer-sponsored health insurance. The lack of a virologic diagnosis of influenza, and an index date based on the first diagnosis of influenza rather than first exposure or symptom onset, may have resulted in a conservative estimate of treatment effect. Conclusions: Oseltamivir may reduce the risk of influenza-related morbidity in children when prescribed upon presentation of clinically diagnosed influenza. The use of oseltamivir in children may play an important role in managing influenza outbreaks.