The World Health Organization (WHO) says there is no clear evidence that the antiviral drug, Tamiflu, prevents complications such as pneumonia.

The announcement by the Geneva-based WHO confirmed a report published by the British Medical Journal on Tuesday, which found there was insufficient data on Tamiflu’s effectiveness.

But a WHO spokesman said the health body would continue to recommend that Tamiflu, made by Swiss drugmaker Roche, be used in certain situations - for people infected with the H1N1 virus who are at high risk of complications or whose symptoms persist for three days or worsen.

The spokesman, Gregory Hartl, said the findings by researchers from the Cochrane Review were “entirely consistent with our views and guidelines. For otherwise healthy people with uncomplicated seasonal influenza, they do not need to be treated with the drugs."

"We need to make very clear that what Cochrane was looking at was seasonal influenza, it was not H1N1," Hartl said.

In the course of the H1N1 pandemic, "a substantial body of evidence has been building up to indicate Oseltamivir [generic name] is effective at reducing and/or preventing severe illness and even death," he added.

Roche has contested the Cochrane Review findings and said it stood behind the previous data showing a benefit.

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