Effectiveness of Oseltamivir in Hospitalized Children With Laboratory-Confirmed Influenza, 2014-2023
Kacie Rytlewski, Angela Dunn, Alissa O’Halloran, Jennifer Habeck, Isaac Armistead, Nisha B. Alden, Darpun Sachdev, Pam Daily Kirley, James Meek, Kimberly Yousey-Hindes, Satoshi Kamidani, Kyle P. Openo, Patricia A. Ryan, Maya Monroe, Sue Kim, Elizabeth Urlaub, Ruth Lynfield, Melissa McMahon, Chad B. Smelser, Yomei Shaw, Grant Barney, Jemma V. Rowlands, Brenda Tesini, Christina Felsen, Krista Lung, Melissa Sutton, Ann Thomas, H. Keipp Talbot, William Schaffner, Andrea George, Holly Staten, Jessica R. Cataldi, Samuel R. Dominguez, Catherine H. Bozio, Suchitra RaoImportance
National organizations recommend antiviral treatment for hospitalized children with influenza; however, use in this setting has recently declined. Studies of oseltamivir effectiveness in children are limited by misclassification bias, unknown symptom onset date, and incomplete capture of antiviral use prior to admission.
Objective
To assess the association between oseltamivir receipt and intensive care unit (ICU) admission and hospital length of stay (LOS) among pediatric influenza-associated hospitalizations.
Design, Setting, and Participants
This cohort study used data that were obtained from the Influenza Hospitalization Surveillance Network (FluSurv-NET), which conducts US population-based surveillance for laboratory-confirmed influenza hospitalizations for all ages across 13 states. The study data include seasons 2014 to 2015 through 2022 to 2023, excluding 2020 to 2021. Participants included children aged younger than 18 years who were hospitalized with laboratory-confirmed influenza and for whom a respiratory symptom onset date was available. These data were analyzed from October 2024 through May 2026.
Exposures
Oseltamivir receipt as a time-dependent exposure.
Main Outcome(s) and Measure(s)
The primary outcome was time from symptom onset to ICU admission. Secondary outcome was time from admission to discharge (LOS). Adjusted Cox proportional hazard models (aHR) with oseltamivir receipt as a time-dependent exposure were used.
Results
After exclusions, 6044 influenza cases were included in the primary ICU analysis, of whom 4240 (70.2%) received oseltamivir, and 7103 cases were included in the secondary LOS analysis, of whom 5746 (80.9%) received oseltamivir. In the ICU analysis, the median (IQR) age was 3 (1-7) years, 3382 (56%) were male and 3721 (44%) were female, and 2937 (49%) had 1 or more medical comorbidity—the most common of which was asthma in 1547 children (26%). In adjusted models, compared with untreated children, oseltamivir treatment reduced the hazard of ICU admission (aHR, 0.69; 95% CI, 0.60-0.80) and shortened LOS (analyzed as hazard of hospital discharge; aHR, 1.13; 95% CI, 1.06-1.21).
Conclusions and Relevance
In this cohort of children hospitalized with influenza, oseltamivir treatment was significantly associated with a reduced risk of ICU admission by 31% and decreased hospital LOS. These findings demonstrate the benefits of oseltamivir receipt and support current national recommendations for oseltamivir treatment as soon as possible in children hospitalized with suspected or laboratory-confirmed influenza.