Contracts awarded to pharmaceutical firms Roche and GlaxoSmithKline will double stockpiles of the flu-prevention drugs.
The deals mean Department of Health bosses will have an additional 7.6 million treatment courses of Tamiflu (Roche) and 10.6 million treatment courses of Relenza (GlaxoSmithKline), adding up to a total of 33.5 million treatment courses of antivirals in all.
The antiviral drugs will be used to reduce the severity of the illness as well as the chance of complications arising such as pneumonia. Without antiviral treatment, it is estimated up to 750,000 people could die in a UK during a pandemic.
Public health minister Dawn Primarolo said: "The UK is already widely recognised as one of the best prepared countries in the world. The increased flu-drug stockpile means that we should be able to treat everyone who falls ill in a pandemic.
"Antivirals are an important part of our robust countermeasure strategy and will ensure we respond effectively in the event of a flu pandemic."
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