Evid Based Nurs 9:108 doi:10.1136/ebn.9.4.108
  • Treatment

Review: antiviral agents reduce risk of influenza in healthy adults and alleviate symptoms faster than placebo

 Q In healthy adults, do antiviral agents reduce the risk of influenza and improve outcomes in affected people?


GraphicData sources:

Medline (August 2005), EMBASE/Excerpta Medica (June 2005), Cochrane Central Register of Controlled Trials (Issue 3, 2005), and bibliographies of relevant systematic reviews and retrieved trials.

GraphicStudy selection and assessment:

randomised controlled trials (RCTs) that compared amantadine, rimantadine, or neuraminidase inhibitors (oseltamivir and zanamivir) with placebo, no treatment, or symptomatic treatment for prophylaxis or treatment of influenza in otherwise healthy people 16–65 years of age. 53 RCTs met the selection criteria.


cases of symptomatic or asymptomatic influenza (confirmed by laboratory testing) and influenza-like illness (ILI) (clinical criteria only); alleviation of symptoms and viral shedding or load in affected people; and adverse effects.


In prophylaxis trials, amantadine, but not rimantadine, reduced influenza and ILI compared with placebo; neither drug reduced asymptomatic infection (table). In treatment trials, both drugs reduced fever at 48 hours (table), but did not differ from placebo for viral shedding at 5 days. Both amantadine and rimantadine increased adverse effects. In placebo controlled prophylaxis trials, neuraminidase inhibitors reduced influenza but not ILI or asymptomatic infection (table). In treatment trials, these drugs increased symptom alleviation (table), reduced complications, and decreased mean nasal viral titre at 24 hours by 0.62 (95% CI 0.41 to 0.82). Prophylactic use of neuraminidase inhibitors increased nausea.


Amantadine and neuraminidase inhibitors reduce the incidence of symptomatic influenza in healthy adults. Antiviral agents alleviate influenza symptoms faster than placebo but do not eliminate infection or viral shedding.

A modified version of this abstract appears in ACP Journal Club.


  1. Donna Moralejo, PhD, RN
  1. Memorial University School of Nursing
 St John’s, Newfoundland, Canada

      Influenza and ILI are major causes of morbidity and mortality, with implications for healthcare and societal costs. Recent planning for a pandemic has led to efforts to increase vaccination coverage and stimulated interest in antiviral medications. Using the rigorous methodology of systematic review, Jefferson et al compiled the growing body of evidence, which can be confusing because of the use of anti-influenza drugs for either prophylaxis or treatment. The results show that antiviral drugs reduce symptoms of true influenza but are much less or not effective for ILI, which is also caused by other types of viruses. In an average influenza season, only 10–18% of cases with specimens sent for testing are confirmed as true influenza.1 Until rapid testing for influenza is more widely available and reliable, routine use of antiviral medications for all patients is not justified. Less expensive, equally effective options, with fewer adverse effects, are available for symptom relief (eg, antipyretics and decongestants). A key finding was that none of the drugs reduced the risk of asymptomatic infection or completely eliminated viral shedding. Influenza is spread through contact with infected droplets of respiratory secretions. Treating asymptomatic carriers who continue their usual activities may, therefore, increase the risk of infecting others, rather than reducing it.

      Antiviral drugs do have a role in the management of influenza (eg, in patients who are older or younger than the age range studied or who have comorbid diseases that increase their risk of complications from influenza). However, the recommendation by Jefferson et al against the routine use of antiviral agents for influenza is justified. Improved vaccination coverage, frequent hand washing, cough etiquette, and staying home when ill are more reliable strategies for reducing incidence of influenza and ILI.1


      Antiviral agents v placebo for prophylaxis and treatment of influenza in healthy adults*

 Q In healthy adults, do antiviral agents reduce the risk of influenza and improve outcomes in affected people?


      • For correspondence: Dr T Jefferson, Cochrane Vaccines Field, Alessandria, Italy. Jefferson.tom{at}

      • Sources of funding: UK Department of Health; Cochrane Review Incentive Scheme 2005; ASL 20, Alessandria and ASL 19, Asti, Italy.

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