There is no evidence that Tamiflu, the drug being stockpiled by Britain, the United States and Europe, will work if a flu pandemic takes off in humans, according to a review published today by the Lancet medical journal.
None of the four existing drugs against influenza has much effect, the paper says. The authors strongly warn against relying on drugs to stamp out a potential avian flu pandemic, saying complacency could get in the way of more useful public health measures - such as hygiene and isolation - to stop the spread of infection.
Tom Jefferson, author of the review published online, told the Guardian yesterday that he hoped that Tamiflu and the similar drug Relenza would save lives in a pandemic, though they have not reduced mortality among the few flu victims who have taken them.
"I'm a member of the human race. I seriously hope they will be effective," he said. "But relying on a single solution is suicidal."
Sufficient data on the use of the two drugs, known as neuraminidase inhibitors, in a pandemic does not exist, he said. "We're trying to bring people down to earth."
The review says the use of the drugs should not be considered in a pandemic "without concomitant measures, such as barriers, distance and personal hygiene". While the drugs might reduce patients' symptoms, the authors say the use of Tamiflu could actually increase the spread of the flu virus. If people take the drug and have fewer symptoms they may end up going to work and spreading the potentially lethal virus.
Dr Jefferson and colleagues from the Cochrane Vaccines Field looked at all the evidence from trials of the efficacy of all four flu drugs - not just Tamiflu and Relenza but also two older drugs from a different class, amantadine and rimantadine.
The latter two are problematic because their use has rapidly led to the emergence of resistant flu strains and they cause unpleasant side-effects, such as hallucinations. The study, part-funded by the Department of Health, recommends that none of the four should be used for the treatment of ordinary winter flu.
Amantadine and rimantadine should not be used because they do not work and cause unpleasant side-effects. Tamiflu and Relenza reduce the severity of real influenza, but do not work on what are known as "influenza-like illnesses" - viral infections with similar symptoms which cannot be distinguished by the GP from real flu without tests.
By the time tests are done, Relenza and Tamiflu are no use, because they must be given within 48 hours of the onset of flu.
The reviewers believe the two drugs should be kept for pandemic use only, where it will be obvious that the cases doctors see will be genuine influenza.
The review could lead to a change of policy from the World Health Organisation, which recommends countries to use antiviral flu drugs in times of ordinary seasonal flu outbreaks so that health workers can become familiar with their use in case of a pandemic.
The Department of Health, which has ordered 14.6m courses of Tamiflu, said in a statement that it was "completely misleading" to claim Tamiflu and Relenza were ineffective against avian flu.
There was not enough data to draw a conclusion, it said. But it admitted it was looking for a "back-up" strategy. "Tamiflu was chosen on the basis of independent expert advice. Internationally, this is agreed as the product of choice. Our antiviral strategy is kept under constant review and we are looking carefully at alternatives as a possible back-up to Tamiflu." International donors pledged $1.9bn (£1.08bn) yesterday towards a global fund to control bird flu. It was hailed as the biggest financial step yet towards preventing a pandemic.
Most of the money will be spent on improving veterinary medicine in East Asia, which has been the worst affected region since the disease emerged in Hong Kong in the late 1990s.
Among the major contributors at the Beijing conference were the US, which contributed $334m, Japan $159m and Europe $138m. Britain promised $35.5m. The total - roughly half grants and half loans - exceeded World Bank estimates of funding gaps by more than $500m.
Is there a cure for flu?
No. The drugs at best only shorten the bout and reduce the symptoms.
Are all four flu drugs the same?
No. There are two classes. Amantadine and rimantadine are older drugs of one class. Tamiflu and Relenza are a newer class of drugs.
Are any of these drugs effective against normal flu?
Not very. The older drugs are not effective enough to make up for the unpleasant side-effects, the review says. The new drugs help reduce symptoms, but must be given within 48 hours - before a doctor can be sure a patient has flu, and not a virus.