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Oseltamivir (Tamiflu®) antiviral treatment and chemoprophylaxis for influenza


  • Early antiviral treatment can shorten the duration of illness, prevent hospitalizations, and may reduce the risk of complications from influenza (i.e. pneumonia, respiratory failure, death)
  • Antiviral treatment should be started as soon as possible after illness onset, ideally within 48 hours of symptom onset
  • All long-term care facility residents who have confirmed or suspected influenza should receive antiviral treatment immediately
  • Decisions about starting antiviral treatment should not wait for laboratory confirmation of influenza


  • Approximately 70-90% effective in preventing influenza
  • When at least 2 patients are ill with influenza-like illness within 72 hours of each other and at least one resident has laboratory-confirmed influenza: start antiviral chemoprophylaxis for all non-ill residents (including those who received influenza vaccine) and unvaccinated health care personnel
    • May be recommended by Public Health even in the absence of confirmatory testing if more than 1 resident is presenting with acute febrile respiratory illness during a 1 week time span during influenza season. Contact Public Health – Seattle & King County for recommendations: 206-296-4774
  • Vaccinated staff can be administered prophylaxis within 2 weeks of influenza vaccination

Considerations for dosages for treatment and chemoprophylaxis

  • Some patients might need special dosing for treatment and chemoprophylaxis, for example, patients with renal impairment or end stage renal disease (ESRD)
  • Dosing information for clinicians including special dosing considerations is available online.
  • Treatment of influenza is typically for 5 days but longer treatment courses may be considered for patients who remain severely ill after 5 days of treatment
  • Chemoprophylaxis in long term care facilities with influenza is typically for a minimum of two weeks and continuing for 1 week after the last onset of illness

Complete antiviral prescribing guidance