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Biosecurity BriefingStudy Finds Oseltamivir Reduces Mortality in Patients Hospitalized with Influenza By Luciana Borio, November 16, 2007 On November 15, 2007, Clinical Infectious Diseases (CID) released the results of a prospective cohort study which found that when the antiviral drug oseltamivir (brand name Tamiflu®) was administered to adult patients hospitalized with influenza, mortality was decreased by almost 80%.1 Conducted between January 2005 and May 2006, the study monitored death rates among patients with laboratory-confirmed influenza infection for 15 days after onset of symptoms. Of 327 adult patients, median age 77 years, 75% had a chronic underlying illness, and approximately 71% had been vaccinated against influenza (vaccination data was available for only 303 patients). Sixteen percent required ICU admission, and 8.3% died within 15 days after onset of symptoms. Approximately 1/3 of the patients received antiviral therapy. Patients who were prescribed the antiviral drug amantadine were considered as having received no therapy at all because the vast majority of influenza viral isolates during the study period were resistant to amantadine.1 Treatment with oseltamivir was found to be associated with a reduction in risk of death by nearly 80%. However, antiviral therapy was not associated with a shorter hospital stay. The median length of stay for surviving patients who did not receive oseltamivir therapy was 6 days, and for those who received therapy, it was 8 days.1 According to a 2005 article in the New England Journal of Medicine (NEJM), previous trials have shown that antiviral therapy administered to healthy adults up to 48 hours after the onset of symptoms is beneficial in reducing the severity and duration of illness as well as the risk of complications associated with influenza.2 In this CID trial, however, antiviral therapy benefitted older, sicker patients, even when administered after the “48 hour window.” The authors speculate that in healthy adults with influenza, the virus is cleared promptly, precluding any benefit of therapy administered after 48 hours of symptom onset. However, in sicker individuals, viral replication might persist beyond the 48 hour window. Thus, patients may still benefit from antivirals during this time.1 References
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