A new review of data on Tamiflu, a drug commonly prescribed to prevent the spread of influenza, has sparked doubts about the drug's effectiveness.
Scientists say governments that stockpile Tamiflu, from Roche, are wasting billions of dollars, Reuters reports.
The review found that while that and other influenza medicines can shorten flu symptoms by around half a day, there is no good evidence behind claims they cut hospital admissions or lessen complications of the disease.
"There is no credible way these drugs could prevent a pandemic," says Carl Heneghan, one of the lead investigators of the review and a professor of evidence-based medicine at Britain's Oxford University.
The review's main findings were that the medicines had few if any beneficial effects, but did have adverse side effects that were previously dismissed or overlooked.
The report also found the drug had a number of side-effects, including nausea, headaches, psychiatric issues, kidney problems and hyperglycaemia.
"Remember, the idea of a drug is that the benefits should exceed the harms," Heneghan says. "So if you can't find any benefits, that accentuates the harms," Reuters reports.
Researchers say they want governments to rethink stockpiling neuraminidase inhibitors.
Tamiflu, a neuraminidase inhibitor, is approved by regulators worldwide and is stockpiled in preparation for a potential global flu outbreak.
The drug is also on the World Health Organization's "essential medicines" list.
The United States has spent more than $1.3 billion buying a strategic reserve of antivirals including Tamiflu, while the British government has spent almost $703 million (424 million pounds) on a stockpile of some 40 million Tamiflu doses, FOX News reports.
Roche rejected the findings, saying it "fundamentally disagrees with the overall conclusions" of the study.
"We firmly stand by the quality and integrity of our data ... and subsequent real-world evidence demonstrating that Tamiflu is an effective medicine in the treatment and prevention of influenza," it said in a statement.
Tamiflu sales hit almost $3 billion in 2009 - mostly due to its use in the H1N1 flu pandemic - but they have since declined.