The row has drawn in the drugmaker as well as industry regulators and independent scientists. Supporters of Tamiflu said the researchers' conclusions were flawed and insisted the drug is both safe and effective.
No good evidence
The dispute over the benefits of Tamiflu, and to a lesser extent of GlaxoSmithKline's flu drug Relenza, blew up with the joint publication by the respected Cochrane Review research network and the British Medical Journal of an analysis of trial data, which found no good evidence behind claims the drugs cut hospital admissions or reduce flu complications.
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The review's main findings were that the medicines had few if any beneficial effects, but did have adverse side effects that were previously dismissed or overlooked.
"Remember, the idea of a drug is that the benefits should exceed the harms," said Carl Heneghan, one of the lead investigators of the Cochrane review and a professor of evidence-based medicine at Britain's Oxford University. "So if you can't find any benefits, that accentuates the harms."
But Roche, which has been under fire for several years over its refusal to allow the Cochrane team unrestricted access to Tamiflu data, rejected the findings, saying it "fundamentally disagrees with the overall conclusions" of their study.
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"We firmly stand by the quality and integrity of our data, reflected in decisions reached by 100 regulators across the world and subsequent real-world evidence demonstrating that Tamiflu is an effective medicine in the treatment and prevention of influenza," it said in a statement.
Tamiflu sales hit almost $3 billion in 2009 – mostly due to its use in the H1N1 flu pandemic – but they have since declined.
The drug, one of a class of medicines known as neuraminidase inhibitors, is approved by regulators worldwide and is stockpiled in preparation for a potential global flu outbreak. It is also on the World Health Organization's "essential medicines" list.
The United States has spent more than $1.3 billion buying a strategic reserve of antivirals including Tamiflu, while the British government has spent almost 424 million pounds ($703 million) on a stockpile of some 40 million Tamiflu doses.
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Money down the drain
Heneghan's team say their analysis is the first based on full data – from 20 trials of Tamiflu, known generically as oseltamivir, and 26 trials of Relenza, also known as zanamivir.
At a briefing in London to present their findings, Heneghan said the money spent on stockpiles "has been thrown down the drain" because until now, the full data had not been seen by regulators, governments, doctors or patients.
"The original evidence presented to government agencies around the world was incomplete," said Fiona Godlee, editor of the BMJ which has spearheaded a four-year long campaign to force Roche to reveal all its Tamiflu data.
"And when they (the Cochrane review team) eventually received the full information on these drugs, the complete evidence gives a very much less positive picture."
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But adding more heat to the row, the European Medicines Agency (EMA) – which approved the drug for sale in Europe – disputed the claim they had not seen all the Tamiflu data.
Enrica Alteri, head of medicines evaluation, said the EMA had seen and reviewed all 20 studies referred to in the review, adding the latest analysis did not raise any new concerns or alter the agency's assessment that the benefits of Tamiflu outweighed its risks.
No reduction in hospitalisations
The Cochrane review found that compared with a placebo, or dummy pill, Tamiflu led to a quicker alleviation of flu-like symptoms of around half a day (down from 7 days to 6.3 days) in adults, but the effect in children was more uncertain.
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There was no evidence of a reduction in hospitalisations or in serious flu complications such as confirmed pneumonia, bronchitis, sinusitis or ear infections in either adults or children, Heneghan's team said.
Tamiflu also increased the risk of nausea and vomiting in adults by around 4 percent and in children by 5 percent, they said, and there was a reported increased risk of psychiatric events – described as mood changes – of around 1 percent when Tamiflu was used as a preventative drug in uninfected people.
Godlee described the battle with Roche as a "really lengthy cat and mouse, Alice in Wonderland, bizarre experience of trying to get data on a drug which governments around the world were busy buying, stockpiling and spending billions of dollars on".
"Why did no-one else demand this level of scrutiny before spending such huge sums on one drug?" she said. "The whole story gives an extraordinary picture of the entrenched flaws in the current system of drug regulation and drug evaluation."
(Additional reporting by Ben Hirschler; Editing by Tom Pfeiffer)
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