This retrospective cohort study evaluated whether oseltamivir treatment (as a time-dependent exposure) reduces ICU admission risk and hospital length of stay (LOS) in children under 18 hospitalized with laboratory-confirmed influenza across 13 US states over 8 seasons (2014–2023, excluding 2020–2021) using FluSurv-NET data.
Oseltamivir reduced the hazard of ICU admission by 31% (aHR 0.69; 95% CI 0.60–0.80) and shortened hospital LOS (aHR for discharge 1.13; 95% CI 1.06–1.21), corresponding to ~9.4 hours less in hospital (95% bootstrap CI 4.3–14.6 hours). Benefit persisted regardless of timing of treatment initiation or presence of comorbidities.
- Observational design cannot fully exclude unmeasured confounding. - FluSurv-NET covers ~9% of the US population (13 states), limiting generalizability. - Prehospitalization oseltamivir use may be incompletely captured, potentially underestimating the treatment effect.
Start oseltamivir as soon as possible in all children hospitalized with suspected or confirmed influenza — benefit on ICU risk and LOS was seen even with late treatment (≥3 days from symptom onset). Don't withhold treatment based on symptom duration or absence of high-risk comorbidities.
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