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Packets of Tamiflu tablets are stored in the Swiss Army Pharmacy in Ittigen near Bern August 10, 2009.

Concerns are emerging that governments around the world may have wasted billions of dollars and even put people at risk by stockpiling Tamiflu to treat influenza.

A landmark study published on Wednesday in the Cochrane Library, a collection of databases that publishes high-quality research that helps to inform health-care decisions, found no clear evidence that Tamiflu, the brand name of the drug oseltamivir, prevents the spread of influenza or flu complications and suggested that it could even interfere with the effectiveness of vaccines.

But even more worrisome, according to the authors, is the fact that drug maker Roche continues to hold back valuable data from public scrutiny. They are calling on health regulators to demand access to the unpublished data in order to get the full picture on whether Tamiflu works and is safe.

"We cannot afford to continue to waste money like this on treatments that are not effective," said Carl Heneghan, director of the Centre for Evidence-Based Medicine at the University of Oxford and a practising physician who collaborated on the study. "People have got to stop."

Governments around the world invested significant sums of money in antiviral drugs, most notably Tamiflu, which was licensed in 1999 and has been looked to as a treatment that can limit the symptoms of influenza and reduce the risk of transmission. Canada has spent tens of millions stockpiling the drug in case of an influenza pandemic.

A Health Canada spokesman said the department is aware of the study and is reviewing the article and the evidence of claims for Tamiflu.

The study's authors examined thousands of pages of research, including previously unpublished data, into the safety and efficacy of Tamiflu.

They found that while the drug appears to reduce the symptoms of the flu, there is no explanation as to the exact mechanism and how this occurs. As a result, the Cochrane researchers said it is possible that Tamiflu affects antibody production, a claim that Roche has repeatedly denied. This is serious because in order for vaccines to work, they must elicit an antibody response.

Furthermore, there is no clear evidence showing that Tamiflu can reduce the transmission of the virus or complications resulting from infection.

"I would not recommend this treatment and I have not given it to a single patient," Dr. Heneghan said.

What's more, according to lead author Tom Jefferson, a Cochrane review author and independent epidemiologist who is based in Rome, health regulators in the U.S., Britain and elsewhere have been fully aware of these potential drawbacks and have yet to take action. "Why ignore the facts?" he said.

Researchers said Roche must release the full data set regarding Tamiflu in order to allow better understanding of how the drug works and determine the extent of potential problems or drawbacks.

For instance, the research team received access to previously unpublished clinical study reports on Tamiflu through the European Medicines Agency. But when they compared published trials to the complete, but unpublished, trial records, there were inconsistencies, including no mention of some serious adverse events in the published data.

Roche said in a statement that it provided the Cochrane researchers with 3,200 pages of "very detailed information, enabling their questions to be answered." It added that company-sponsored trials on Tamiflu are available as peer-reviewed publications or in summary form from

Health Canada and the Public Health Agency of Canada had full access to clinical trial data and it is their role to review that information to make a decision about whether drugs should be given licences for use, the Roche statement said.

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