Researchers who have fought for years to get full data on Roche's flu medicine Tamiflu said on Thursday that governments who stockpile it are wasting billions of dollars on a drug whose effectiveness is in doubt. In a review of trial data on Tamiflu, and on GlaxoSmithKline's flu drug Relenza, scientists from the respected research network the Cochrane Review said that the medicines had few if any beneficial effects, but did have adverse side effects. Remember, the idea of a drug is that the benefits should exceed the harms," Heneghan said. "So if you can't find any benefits, that accentuates the harm." Tamiflu sales hit almost $3 billion in 2009 - mostly due to its use in the H1N1 flu pandemic. The drug, one of a class of medicines known as neuraminidase inhibitors, is approved by regulators worldwide and is stockpiled in preparation for a potential global flu outbreak. It 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 424 million pounds ($703 million) on a stockpile of some 40 million Tamiflu doses. There was no evidence of a reduction in hospitalizations or in flu complications ... and Tamiflu also increased the risk of nausea and vomiting in adults by around 4 percent and in children by 5 percent.