The drug is a household name with millions of doses stockpiled against the threat of a potential flu pandemic and talked about alongside aspirin and penicillin as a wonder drug.
But now scientists are set to raise serious questions about the effectiveness of Tamiflu, its side-effects and the opaque way drugs get approved for widespread use on the NHS.
While the full results of the Cochrane Collaboration review into Tamiflu will not be known until tomorrow, the Department of Health is bracing itself for awkward questions about whether it rushed headlong into mass prescriptions in the wake of the 2009 swine flu outbreak.
Cochrane, a non-profit group dedicated to analyzing medical evidence, brings together the combined results of the world's best medical research studies, and are recognised as the gold standard in evidence-based health care. But during their two-year study into Tamiflu, researchers claimed they were hampered in their efforts to fully appraise the drug by the refusal of its manufacturer, Roche, to hand over all the raw data used to support their claims.
Professor Sir Iain Chalmers, a founder of the Cochrane Collaboration, told The Bureau of Investigative Journalism: "We have invested millions of pounds on stockpiling Tamiflu on the basis of a paper that presented the results of 12 trials, only two of which have been published. The investigation... shows Roche refused to provide data to evaluate these trials. Investigators got some data through the European Medicines Agency, but this doesn't answer all of the questions they have."
He added: "It is a disgrace that Roche have not provided this data."
Tom Jefferson, the lead author of the study, said he was very concerned about the unwillingness of Roche to provide all the raw data. It is understood the European Medicines Agency that approved Tamiflu also only saw a proportion of the drugs trial results. The US Food and Drug Administration is thought not to have reviewed the largest ever trial of Tamiflu when considering it for approval.
Roche said it had made full clinical study data available to health authorities for their review as part of the licensing process. It added that "all completed" Roche-sponsored studies on the safety and efficacy of Tamiflu were available as peer-reviewed publications or in summary form. It said it had provided the Cochrane group with access to 3,200 pages of very detailed information.
"Roche stands behind the robustness and integrity of our data supporting the efficacy and safety of Tamiflu," the company said.
A DoH spokesman said: "At the end of last year we published a major review of the scientific evidence base, which showed a clear benefit in offering antivirals to those with severe illness and those with additional risk factors... Our priority has always been to minimise the risk of serious illness and death from seasonal flu."