Two antiviral drugs have mediocre effects on relieving flu symptoms, according to a review by independent experts that raises questions about the value of medications stockpiled by Canadian authorities in case of a flu pandemic.

Federal and provincial governments have stored and refreshed their supplies of antivirals, mainly oseltamivir (often known by its brand name Tamiflu), as part of their emergency plans for a possible pandemic of bird flu, such as H5N1 back in 2004. The drugs were also widely used in the H1N1 swine flu outbreak in 2009.

In Wednesday’s Cochrane Review, pharmacy professor Peter Doshi of the University of Maryland and his co-authors reviewed randomized, placebo-controlled trials involving more than 24,000 people and data from regulators in the U.K., U.S., Europe and Japan to check the effectiveness of Tamiflu and another antiviral that is inhaled, zanamivir (also known as Relenza).

"There is no good evidence that the drug [Tamiflu] saves lives," Doshi said in an interview. "There is no good evidence that it reduces hospitalizations, no good evidence that it reduces the risk of complications, no evidence that the drug will interrupt the spread of the virus, that's person to person transmission —  some of the major reasons why the drug was stockpiled."

Tamiflu treatment also increased the risk of vomiting in adults and children.

Tamiflu

The antiviral Tamiflu is part of federal and provincial stockpiles and is used during regular flu seasons, as preventive medication during outbreaks in long-term-care facilities and in case of a pandemic. (Nigel Marple/Reuters)

Prof. Barbara Minztes of the School of Population and Public Health at the University of British Columbia reviewed Tamiflu for the B.C. government.

"I think the study raises some very important questions, that if the government, these governments had had full access to all of the scientific evidence before those decisions were made, would they have made that same decision to stockpile the drugs?"

At a previously planned meeting of federal, provincial and territorial public health officers in Toronto today, they talked about the stockpile question. Over the last decade, governments in Canada have spent more than $180 million on the antiviral stockpiles.

"We will be continuing to have collective discussions and decisions around whether we replace the existing stockpiles, if we do, how much or do we not replace them at all? Those are all questions that we have to grapple," said Dr. Robert Strang, chair of the Council of Chief Medical Officers of Health.

The stockpiles are used during regular flu season, as preventive medication during outbreaks in long-term care facilities and in case of a pandemic.

"One of the things we're doing is reviewing our whole national pandemic plan, and part of that is we will be moving forward in the coming months looking at antivirals and the role they play in dealing with influenza, both seasonal flu and in pandemics. So this new study will just be part of that review," Strang said.

Research transparency and public health decisions

It took the Cochrane Collaboration, an international network of scientists, 4½ years to pressure Roche into releasing the unpublished data from its Tamiflu clinical trials. Until now, the company had only published its positive findings, a common practice in the industry.

Doshi and others say the new report unmasks medical journals that publish incomplete research, and regulators and governments that make public health decisions based on industry-funded research without requiring independent review.

Strang also pointed to another study, funded by Tamiflu's manufacturer, Roche, that suggested use of antivirals did help save lives among people who were hospitalized during H1N1. The study was not a randomized trial, the gold standard in medical research.

Tamiflu's manufacturer, Roche, said its medicine is being misrepresented.

"Roche fundamentally disagrees with the overall conclusions of the Cochrane Acute Respiratory Infections Group’s (ARI) report on Tamiflu," the company said in a release.

"Roche welcomes third-party research and is dedicated to sharing clinical data for our medicines in the interest of advancing science. However, we do not consider the ARI Group, who have identified themselves as inexperienced in dealing with such data, to be the final authority on the value of neuraminidase inhibitors."

The Public Health Agency of Canada said it closely monitors the scientific literature related to the effectiveness of antivirals for the prevention and treatment of influenza, and it says the balance of evidence supports their use.

As of this month, the federally owned stockpile of emergency supplies has about 9.1 million doses of Tamiflu and 10.6 million doses of Relenza, which are meant to provide surge capacity to provinces and territories if needed, the agency said in an email.

Tamiflu sales hit almost $3 billion US in 2009 and have since declined.

With files from CBC's Frederic Zalac