Antiviral Oseltamivir Reduces Mortality Risk in Older Adults Hospitalized with Influenza: Study
According to a Canadian study published today in Open Forum Infectious Diseases, adults aged 65 and older experienced a significant reduction in mortality risk when treated with the antiviral oseltamivir (Tamiflu) during influenza-related hospitalizations, regardless of their vaccination status.
Oseltamivir is recommended for the treatment of adults hospitalized with influenza, but adherence is often suboptimal.
This may be due to doubts about the reliability of the evidence supporting its benefits, particularly when initiation is delayed. We aimed to assess the effectiveness of oseltamivir in reducing mortality in older adults hospitalized with influenza, with a focus on the timing of initiation.
The CIRN-SOS Network gathered data on severe respiratory illnesses across five Canadian provinces during the influenza seasons 2012-2019. Individuals aged 65+ years with confirmed influenza and available antiviral prescription data were included. We compared the 30-day survival rates of hospitalized patients based on oseltamivir prescription status. Kaplan-Meier estimated survival probability and IPT-weighted Cox proportional hazard models were used to calculate hazard ratios (HR) and 95% confidence intervals (CIs) for mortality.
The analyses considered the time to antiviral initiation. Results: Among the 8,135 influenza patients studied, 2,126 did not receive antiviral treatment, whereas 6,009 were treated with oseltamivir. A total of 395 patients were hospitalized for more than 30 days.
The overall mortality rate was 8.32 per 1,000 person-days, with 53.9% of the deaths occurring within the first week. Oseltamivir recipients had a 18% lower risk of 30-day mortality. The benefit was significant for influenza A but not for influenza B. Oseltamivir remained effective even when initiated after 48 hours.
Influenza vaccination did not mediate the effectiveness of oseltamivir in reducing mortality. Oseltamivir significantly reduces mortality risk in older adults hospitalized with influenza, even when administered after 48 h, independent of vaccination status.
Henrique Pott, Melissa K Andrew, Zachary Shaffelburg, Michaela K Nichols, Lingyun Ye, May ElSherif, Todd F Hatchette, Jason LeBlanc, Ardith Ambrose, Guy Boivin, William Bowie, Jennie Johnstone, Kevin Katz, Phillipe Lagacé-Wiens, Mark Loeb, Anne McCarthy, Allison McGeer, Andre Poirier, Jeff Powis, David Richardson, Makeda Semret, Stephanie Smith, Daniel Smyth, Grant Stiver, Sylvie Trottier, Louis Valiquette, Duncan Webster, Shelly A McNeil, on behalf of the Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN) and the Toronto Invasive Bacterial Diseases Network (TIBDN), Oseltamivir Reduces 30-Day Mortality in Older Adults with Influenza: A Pooled Analysis from the 2012-2019 Serious Outcomes Surveillance (SOS) Network of the Canadian Immunization Research Network (CIRN), Open Forum Infectious Diseases, 2025;, ofaf058, https://doi.org/10.1093/ofid/ofaf058
