University of Leicester eBulletin

New Flu Drugs are Effective, But Have Important Limitations

June 2003

Effectiveness of neuraminidase inhibitors in treatment and prevention of influenza A and B: systematic review and meta-analyses of randomised controlled trials BMJ Volume 326, pp 1235-40 Editorial: Preventing and treating influenza BMJ Volume 326, pp 1223-4

Evidence suggests that two new antiviral drugs (oseltamivir and zanamivir) are effective for treating and preventing flu, but more research is needed to clarify who will benefit most from treatment, concludes a study in this week's BMJ.

Researchers analysed 17 treatment trials and 7 prevention trials of oseltamivir and zanamivir in three population groups (children, high risk adults, and otherwise healthy adults). All trials compared one of the drugs against placebo or standard care.

They found that treating otherwise healthy adults and children with zanamivir and oseltamivir reduced the duration of symptoms by up to one day. Giving zanamivir and oseltamivir to prevent flu cuts the odds of developing flu by 70-90%, depending on the strategy adopted and the population studied.

The drugs also provided a 29% to 43% reduction in the odds of complications requiring antibiotics when given within 48 hours of onset of symptoms. However, the results were less conclusive in the high-risk population, and little evidence exists on serious complications requiring admission to hospital or causing death or on adverse events, add the authors.

Although evidence supports the clinical effectiveness of both oseltamivir and zanamivir for the treatment and prevention of flu, research is needed into the comparative effectiveness of these drugs with one another and the potential 'added value' of these drugs compared with or in combination with flu vaccine, they conclude.

Zanamivir and oseltamivir have been welcomed as long awaited additional tools for treatment and prevention. However, in terms of meeting public health objectives, they have important limitations, says Klaus Stohr of the World Health Organisation in an accompanying editorial.

Promising research is under way to develop new neuraminidase inhibitors that are more efficacious, cost less, and are simpler to prescribe. It is to be hoped that they are available before the next pandemic strikes, he concludes.


Paper: Nicola Cooper, Research Fellow, Department of Epidemiology and
Public Health, University of Leicester, Leicester, UK, telephone +44 (0)116 252 5437, email

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