Utility of zanamivir for chemoprophylaxis of concomitant influenza A and B in a complex continuing care population

Abstract

Objective: To describe compliance with and the safety and prophylactic efficacy of zanamivir among patients at risk of developing influenza-related complications after exposure to both influenza A and B viruses.

Design: Nonrandomized trial using both historical and contemporaneous controls from ward populations within the same facility.

Setting: A 547-bed urban hospital providing complex continuing care and rehabiltation.

Patients: Fifty patients on a single ward concomitantly exposed to both influenza A and B during an influenza outbreak.

Interventions: All patients were screened for symptoms of influenza and nasopharyngeal swabs were sent for viral culture prior to treatment (two oral inhalations [2 x 5 mg] twice daily for 5 days) or prophylaxis (two oral inhalations [2 x 5 mg] once daily for 14 days) with zanamivir. Patient symptoms, compliance, and drug tolerance were monitored daily. Demographic data, comorbidities, vaccination status, and functional status (Katz score) were collected for all patients.

Results: The mean age of the patients was 70.6 years (standard deviation, +/- 16.4 years). Ninety-four percent had two or more comorbidities, 71% were dependent in two or more activities of daily living, 63% had been vaccinated for influenza, and 82% had received amantadine. Zanamivir was well tolerated, with 93% of the patients completing their course. The efficacy for preventing symptomatic infection was 82% and 91% (95% confidence interval, 62% to 98%) based on historical and contemporaneous controls, respectively.

Conclusion: These data suggest that zanamivir can be used safely and effectively as a prophylactic agent in the management of influenza outbreaks in a complex continuing care population with multiple comorbidities.