Risk of pneumonia and other complications of influenza-like illness in patients treated with oseltamivir

Background: Clinical trials suggest that the risk of pneumonia and other sequelae of influenza may be reduced in patients using oseltamivir. Research design and methods: This retrospective cohort study used U.S. health insurance claims data. Patients were grouped into three cohorts: (1) diagnosed with influenza-like illness (ILI) and received a dispensing of oseltamivir; (2) diagnosed with ILI but received no antiviral medication; and (3) received oseltamivir without a physician diagnosis of ILI. Baseline factors assessed included demographics, history of drug dispensings, diagnoses, and vaccinations. Main outcome measures: Outcomes included diagnosis of pneumonia, dispensing of an antibiotic, or hospitalization within 30 days after an ILI diagnosis or oseltamivir dispensing. Results: The adjusted hazard ratio for ILI with oseltamivir compared to ILI without antivirals for pneumonia was 0.72 (95% CI, 0.60-0.86), for antibiotic dispensing was 0.89 (95% CI, 0.86-0.93), and for hospitalization was 0.74 (95% CI, 0.61-0.90). The cohort who received oseltarnivir without an ILI diagnosis did not differ significantly in risk of any outcome from the ILI with oseltamivir cohort. Conclusions: The risk of pneumonia, antibiotic dispensing, and hospitalization was reduced in patients with ILI who received oseltarnivir compared to no antiviral therapy. These findings were based on health care claims only and have not been verified through medical record review.