The World Health Organisation on Friday stood by its advice on the use of Tamiflu in high risk swine flu patients, insisting that it was effective in those cases despite a study questioning the antiviral drug.
WHO spokesman Gregory Haertl said the UN agency was not challenging the international scientific study's findings on Tamiflu treatment for seasonal flu in otherwise healthy patients.
However, he insisted that there was "substantial" evidence since the pandemic A(H1N1) strain emerged in April showing that the basic drug, oseltamivir, was an effective treatment for swine flu in high risk groups, including those who already had other ailments.
"We do need to keep in mind the fact that there is a small minority of cases that do become severe and, in those cases and in people who are in high risk groups, we very firmly recommend that oseltamivir be used," Haertl told journalists.
The updated "Cochrane review" published in the British Medical Journal this week said such drugs only had "modest effectiveness against the symptoms of influenza in otherwise healthy adults."
Haertl said: "We need to make very clear that what Cochrane was looking at was seasonal influenza, it was not H1N1, and we do not have any disagreement with Cochrane concerning what they looked at."
"However, over the last eight months in the course of the pandemic a substantial body of evidence has been building up to indicate that oseltamivir is effective at reducing and or preventing severe illness or even death in, above all, populations who are at risk to begin with and in populations who develop severe illness," he added.