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Original Investigation
November 27, 2000

Impact of Zanamivir on Antibiotic Use for Respiratory Events Following Acute Influenza in Adolescents and Adults

Author Affiliations

The Department of Internal Medicine, Division of Epidemiology and Virology, University of Virginia School of Medicine, Charlottesville (Drs Kaiser and Hayden); Glaxo Wellcome Inc, Research Triangle Park, NC (Drs Elliot and Hammond); and Glaxo Wellcome Research and Development, Greenford, England (Mr Keene). Dr Kaiser is now with the Division of Infectious Diseases, University Hospital, Geneva, Switzerland.

Arch Intern Med. 2000;160(21):3234-3240. doi:10.1001/archinte.160.21.3234

Background  Influenza infections commonly lead to respiratory tract complications that result in antibiotic treatment.

Objectives  To determine frequency of respiratory events leading to antibiotic use following influenza illness in adolescents and adults, and to assess whether treatment with topical zanamivir prevents these complications.

Methods  Meta-analysis of 7 randomized, double-blind, placebo-controlled trials; 3815 mainly healthy adolescents and adults (mean age, 34 years) with an influenzalike illness of less than 2 days' duration were randomly assigned to receive combined inhaled and intranasal zanamivir, inhaled zanamivir, or corresponding placebos. Twelve percent of enrolled subjects were high-risk patients. The main outcome was the incidence of respiratory events leading to antibiotic prescriptions in patients with proven influenza.

Results  Influenza infections were laboratory confirmed in 2499 (66%) of 3815 patients (influenza A in 88% and B in 12%). Placebo recipients developed a respiratory event leading to antibiotic use in 17% of cases, mainly for acute bronchitis or acute sinusitis. Among zanamivir-treated patients (n = 1494%) the incidence of respiratory events leading to the use of antimicrobials was 11% (relative risk [RR] compared with placebo, 0.69; 95% confidence interval [CI], 0.57-0.84). Intranasal and inhaled zanamivir seemed to reduce the number of upper (RR, 0.59; 95% CI, 0.36-0.97) and lower respiratory tract events (RR, 0.64; 95% CI, 0.38-1.08). Inhaled zanamivir reduced the number of lower respiratory tract events (RR, 0.60; 95% CI, 0.42-0.85), but the reduction in the number of upper respiratory tract events was not statistically significant (RR, 0.90; 95% CI, 0.63-1.27).

Conclusions  Respiratory complications or worsening of symptoms leading to antibiotic use occurred in about 17% of adolescents or adults with influenza infection. Early treatment of influenza illness with zanamivir reduced the number of these antibiotic prescriptions.