The national stockpile of 30 million doses will be available for the coming flu season, when swine flu is expected to circulate. But it expires in October 2011 and doses not used this winter will be unusable by next year's flu season, the DoH confirmed.
Last week, DoH accounts revealed it lost more than £200 million on unused monovalent swine flu vaccine and antivirals in 2009/10. The DoH wrote off the loss but said the vaccine would be kept for future use.
However, the impending expiry means much of this stock will go unused, because this year's trivalent seasonal flu jab contains swine flu antigens. This will be given to most at-risk groups instead of the monovalent vaccine.
With a global surplus of vaccine at present, it is also unlikely the DoH will be able to sell off unused vaccine before the 2011 deadline.
A spokeswoman said: 'Requests from other governments for supplies from our reserve of vaccine would be considered at the time.'