Characterizing Oseltamivir Use among Community-Dwelling Patients Diagnosed with Influenza Virus Infection, 2023-2025

Background: Oseltamivir is an antiviral medication for influenza that can reduce the duration of symptoms and may lower the risk of some complications. Recommendations for use of oseltamivir include in the outpatient setting for individuals at higher risk of developing influenza complications. Objectives: To describe oseltamivir initiation and treatment completion among influenza-positive outpatients and identify factors associated with each. Methods: In a U.S. outpatient household transmission study, index participants with laboratory-confirmed influenza provided up to 12 days of detailed information on medication use. We described oseltamivir initiation among index cases and treatment course completion of [&ge;] 10 doses among cases who initiated oseltamivir. We used unadjusted and adjusted logistic regression to identify factors associated with initiation and course completion. Results: Among 823 enrolled index cases, 324 (39%) initiated oseltamivir treatment. Of 406 persons at higher risk for influenza complications, 172 (42%) initiated treatment. Oseltamivir initiation was lowest among children aged 2 to < 5 years (19%) compared to all other age groups. Among 313 cases who initiated oseltamivir, 42% completed the recommended treatment course of [&ge;] 10 doses. Among 163 individuals at higher risk of influenza complications, 69 (42%) completed the recommended treatment course of [&ge;] 10 doses. Children < 2 years were significantly less likely to complete treatment compared to adults aged 18-50 years (aOR: 0.21, 95% CI: 0.04, 0.78, p= 0.030); reasons for discontinuation could not be determined. Conclusions: These findings reveal differences in oseltamivir treatment in an outpatient setting among groups at higher risk for influenza complications.