In a ministerial statement to the Assembly, health minister Michael McGimpsey said there were currently stocks to cover half the population, but extra stocks were being bought to increase cover to 80%.
The move mirrors that of the DoH in England which ordered an additional 16 million doses of Tamiflu to bring the stockpile for England up to 50 million.
Stocks of antibiotics are also being increased in Northern Ireland in case they are needed to treat complications of the virus, such as pneumonia.
Currently, there have been 28 confirmed cases of A(H1N1) influenza in the UK, but no cases in Northern Ireland.
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