Antiviral Dispensing for Influenza Outpatients Younger Than 65 Years With Comorbidities: A Retrospective Cohort Study

Background: Real-world evidence on antiviral dispensing for influenza outpatients with underlying medical conditions (UMCs) is limited. We characterized dispensing among influenza outpatients aged <65 years with UMCs, comparing commercial and Medicaid coverage. Methods: We used outpatient encounter claims from the US MarketScan Commercial and Medicaid databases during October-April of the 2018-2019 through 2023-2024 influenza seasons and October-December 2024-2025. Eligible encounters included patients aged <65 years with a clinical influenza diagnosis, ≥1 UMC, and ≥12 months of continuous enrollment before diagnosis. Antiviral treatment was defined as dispensing of oseltamivir, peramivir, zanamivir, or baloxavir within 7 days of the encounter. We described demographic, clinical, and care-seeking characteristics and evaluated overall and same-day dispensing by insurance type. Results: Among 549 424 encounters, 268 463 (48.9%) were commercially insured (median age 19 years [interquartile range, IQR, 8-44]) and 280 961 (51.1%) were Medicaid insured (median age 10 years [IQR 5-18]). Chronic pulmonary disease was the most common UMC (88.0% and 81.8%). Antivirals were dispensed in 54.2% (commercial) and 53.7% (Medicaid) of encounters, almost exclusively oseltamivir. Same-day dispensing occurred in 91.1% of commercial and 81.4% of Medicaid encounters. Overall dispensing was lowest among patients with emergency department encounters or multiple outpatient visits; same-day dispensing was lowest among those with multiple UMCs, emergency department encounters, or multiple visits. Dispensing increased with age in commercial encounters but declined among adults with Medicaid. Conclusions: About half of higher-risk influenza outpatients received antivirals. Overall dispensing was similar by insurance type, but Medicaid patients and those with multiple UMCs had greater delays.