An updated expert review says there is no clear evidence that the antiviral drug most commonly used against influenza - oseltamivir (Tamiflu) - prevents complications like pneumonia in healthy people, according to a joint investigation by the BMJ and Channel 4 News.
The claims about the effectiveness of oseltamivir against complications have been a key factor in decisions by governments around the world to stockpile these drugs as part of global pandemic preparedness plans. The UK government has spent an estimated £500m.
The expert review published on BMJ.com today has led to a joint investigation by Channel 4 News and the BMJ into oseltamivir.
The study, which updates a 2006 review published in The Cochrane Library, acknowledges that oseltamivir and other neuraminidase inhibitors have a modest effect in reducing flu symptoms and infectivity in otherwise healthy adults by about one day, but the researchers say that there is insufficient published data to know if oseltamivir reduces complications in otherwise healthy adults.
Dr Fiona Godlee, Editor in Chief of the BMJ, warns that this updated review leaves important questions about effectiveness unresolved. "Governments around the world have spent billions of pounds on a drug that the scientific community now finds itself unable to judge," she says.
Roche, which produces oseltamivir, has estimated sales of £1.6bn this year alone from the drug.
The use of neuraminidase inhibitors, especially oseltamivir, has increased dramatically since the spread of the influenza A/H1N1 (swine flu) pandemic began in April 2009. In the absence of an effective vaccine and because of resistance to previous drugs used against flu, neuraminidase inhibitors were seen as the answer to the pandemic.
The research team, led by Professor Chris Del Mar from Bond University in Australia, analysed 20 published trials that focused on prevention, treatment and adverse reactions.
But their investigation was hampered by the "paucity of good data" available from authors and Roche (the company that produces oseltamivir). Hence the team dropped eight key trials which were never fully published that were included in the earlier review because they were unable to independently verify the results. As a result, they conclude that they have no confidence in claims that oseltamivir reduces the risk of complications of influenza in otherwise healthy adults, and believe it should not be used in routine control of seasonal influenza.
This inability to access the data means that previous evidence on the effects of oseltamivir on flu complications may be unreliable, and they call on governments to set up studies to monitor the safety of neuraminidase inhibitors.
Professor Nick Freemantle and Dr Melanie Calvert from the University of Birmingham reviewed observational studies based on a list provided to the Cochrane authors by Roche. They conclude that "oseltamivir may reduce the risk of pneumonia in otherwise healthy people who contract flu. However, the absolute benefit is small, and side effects and safety should also be considered."
They are critical of the data and say: "Interpretation of the studies was difficult … It seems likely that some patients were included in more than one study, which undermines the ability of these studies to provide independent estimates."
Professor Freemantle says he sees "very little evidence to support the widespread use of oseltamivir in the otherwise healthy population who are developing signs of influenza like illness." He adds: "We have remarkably few resources in this country to spend on pharmaceuticals on health and it's surprising to see such widespread use of oseltamivir. But I suppose that once you've gone and bought lots of doses then it's a bit like the situation with gun control in the US. If you have a gun in the house it's much easier to use it. But it does not mean it's the right thing to do."
Dr Fiona Godlee and Professor Mike Clarke, Director of the UK Cochrane Centre, say this updated review is important because it calls into question "not only the effectiveness of oseltamivir but the whole system by which drugs are evaluated, regulated and promoted."
In a response Roche said that they "firmly believe in the robustness of the data". They point out that full access to data has been granted to governments and regulatory authorities.
As a result of this investigation, Roche has committed to make all study summaries of oseltamivir – including key data – available on a password-protected site. But until then, the Cochrane authors say that "any claims regarding a reduction in risk of serious complications from influenza in healthy adults still cannot be verified."
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