Tamiflu effectiveness questioned

The effectiveness and safety of the anti-influenza drug Tamiflu has been cast into doubt by experts.

An international team of researchers said that while the drug reduces the duration of flu symptoms, there is no clear evidence that Tamiflu prevents complications and reduces the number of people needing hospital treatment, as claimed by the pharmaceutical company Roche.

Tamiflu is now the drug of choice to treat influenza in the UK. At the peak of the swine flu pandemic, the UK had ordered enough Tamiflu to treat 80 per cent of the population.

Billions of dollars have been spent by countries stockpiling the drug to help prevent the spread of flu, but the researchers from the Cochrane Collaboration said there was no trial data to suggest the drug actually did this.

The researchers analysed 16,000 pages of clinical trial data on the effectiveness of the drug.

They said their efforts were hampered by Roche continuing to refuse them access to "key Tamiflu trial data", leaving critical questions about how the drug worked "unresolved."

They also found inconsistencies between reports published in journals and some clinical studies held by the European Medicines Agency (EMA). Theses inconsistencies "led us to lose confidence in the journal reports", they wrote in the British Medical Journal (BMJ).

The Cochrane team also said the side-effects of the drug were "possibly under-reported," and questioned the effect of Tamiflu on the immune system.

According to researchers, Tamiflu appears to affect antibody production, an important finding as the flu vaccine works by stimulating an antibody response.

Although Roche denies this, they refused to explain how the drug works when asked to do so by the BMJ.

The Cochrane Group wrote: "Until more is known about the mode of action of neuraminidase inhibitors, health professionals, patients and other decision makers need to reflect on the findings of this review before making any decision about the use of the drug."

Roche said they provided the Cochrane team with enough information to conduct their evaluation, but the researchers maintain this is not the case.

Dr Peter Doshi from Johns Hopkins University School of Medicine, who led the review, said: "In the BMJ in December 2009, Roche promised full study reports to any legitimate investigators. They have not provided a single full study report to Cochrane, despite our repeated requests."

This article was published on Wed 18 January 2012