A retrospective analysis of more than 11,000 patients hospitalized for influenza found that early treatment with oseltamivir reduced in-hospital mortality, decreased 30-day readmission rates, and increased the likelihood of earlier discharge compared with supportive care.1 The researchers said the study supports current guidelines recommending oseltamivir treatment for all patients hospitalized with severe influenza.
“There is a bit of skepticism about the effectiveness of oseltamivir because most of the efficacy data are based in [outpatient clinics], so we didn’t know when we first designed the study if we were going to see a benefit or not,” said lead author Anthony Bai, MD, MSc, Assistant Professor of Infectious Diseases at Queen’s University, Kingston, Canada. “Our study provides further supporting evidence that patients admitted to the hospital with influenza should be considered for oseltamivir treatment because of a possible benefit in terms of mortality, pending future trial data.”
Researchers analyzed treatment and outcomes for 11,073 patients hospitalized for influenza across 30 hospitals in Ontario, Canada, during nine flu seasons from the 2014 to 2015 season through the 2022 to 2023 season. Of the total population, 69% received oseltamivir on the day of admission or the next day, whereas 31% received supportive care. Patients were generally older, with a mean age of 72.4 years, and 53% were female.
Patients were followed from admission through 30 days following discharge. The primary outcome was all-cause, in-hospital mortality. Secondary outcomes included time to discharge alive, transfer to ICU within 48 hours of initial admission, and readmission within 30 days for any reason.
“I wasn’t surprised by the results because there are guidelines recommending oseltamivir,” said Christina Thornton, MD, PhD, Assistant Professor of Medicine and Microbiology, Immunology, and Infectious Diseases at the University of Calgary, Calgary, Canada. “What I was surprised at was the lack of strong evidence for the guidelines. Many of the studies were quite small and limited. We haven’t had this kind of data before.”
The in-hospital mortality rate was 3.5% for the oseltamivir group vs 4.9% for the supportive care group. The adjusted risk difference was -1.8% (95% CI, -2.8% to -0.9%). Patients in the oseltamivir group were more likely to be discharged earlier with a median length of stay of 4.4 days vs 4.9 days for the supportive care group with an adjusted subdistribution HR of 1.20 (95% CI, 1.15 to 1.25; P < .001). Patients receiving oseltamivir were numerically less likely to be readmitted to the hospital within 30 days, 8.5% vs 9.8%, and less likely to be transferred to ICU care, 1.2% vs 2.0%.
The study numbers are large, Dr. Bai noted, but retrospective analysis of administrative data is not ideal, and there could be residual confounding. However, the results from this study are consistent with earlier observational studies. The global Randomised Evaluation of COVID-19 Therapy (RECOVERY) trial is currently evaluating oseltamivir vs supportive care in patients admitted to the hospital with influenza. The results will help provide more definitive evidence on the benefit of oseltamivir treatment in patients who are hospitalized.
The current results could also lead to a quality improvement (QI) study based on electronic medical record (EMR) prompts, Dr. Thornton added.
“A QI study to actually implement oseltamivir treatment could be really interesting,” she said. “When someone tests positive for influenza, there is an automatic EMR prompt to initiate oseltamivir. We already have guidelines recommending treatment, but it may not be top of mind for hospitalists. And we get influenza results so quickly now with rapid testing that you can start treatment quite early, maybe even in the emergency room.”
References
1. Bai AD, Srivastava S, Al Baluki T, Razak F, Verma AA. Oseltamivir treatment vs supportive care for seasonal influenza requiring hospitalization. JAMA Netw Open. 2025;8(6):e2514508. doi:10.1001/jamanetworkopen.2025.14508
