Authors' objectives:

This review aims to answer the following questions:

1. How effective is zanamivir in shortening the time-course, reducing the severity of illness or preventing death in otherwise healthy adults with influenza?

2. How effective is zanamivir in shortening the time-course, reducing the severity of illness or preventing death in adults at risk of suffering severe adverse outcomes from influenza?

3. What is the frequency and severity of adverse effects associated with the use of zanamivir in both healthy and at-risk adults?

4. What is the cost-effectiveness of zanamivir for the treatment of influenza in healthy and at-risk adults?

Authors' results and conclusions: Effectiveness in all adults: The results of ten trials were included in the review of effectiveness in all adults. Where possible, they were combined in pooled analyses. Inhaled zanamivir 10 mg twice daily for 5 days (the licensed dose) was found to reduce the duration of symptoms of influenza by 1 day from about 6 to 5 days and the time to return to normal activities by 0.5 days from about 7 to 6.5 days in the intention-to-treat population (ITTP). In the influenza-positive population (IPP), the treatment effect was marginally larger but this was not significantly different from that in the ITTP. Effectiveness in at-risk adults: The results of seven trials contributed to the review of effectiveness in at-risk adults. Only one trial recruited an exclusively at-risk population. Six trials in all adults provided data from at-risk subgroups. The pooled analysis was based on 371 in the zanamivir group and 392 in the placebo group. Inhaled zanamivir 10 mg twice daily for 5 days was found to reduce the duration of symptoms of influenza by 1.16 days from about 8 to 7 days in the ITTP and by 1.67 days in the IPP. The data did not have the power to demonstrate any differences in hospitalisation or death rates for either group. The drug had a similar adverse event profile to the placebo group.

Authors' recommendations: The evidence base for at-risk adults has greatly increased since this product was first reviewed by the National Institute for Clinical Excellence (NICE). The data available suggest that it may prove useful when used judiciously in at-risk patients. It will be important to monitor its use and incorporate new trial evidence as it becomes available to confirm this.

Authors' methods: Systematic review, economic evaluation

Project Status: Completed

URL for project: http://www.hta.ac.uk/1172

Year Published: 2002

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: England, United Kingdom

Organisation Name: NIHR Health Technology Assessment programme

Contact Address: NIHR Journals Library, National Institute for Health and Care Research, Evaluation, Trials and Studies Coordinating Centre, Alpha House, University of Southampton Science Park, Southampton SO16 7NS, UK

Contact Name: journals.library@nihr.ac.uk

Contact Email: journals.library@nihr.ac.uk

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