The swine-flu vaccine deal between the government and GlaxoSmithKline has been cut to two-thirds of the original value for just over a third of the doses.
The Department of Health said the UK order with Glaxo would be capped at 34.8 million doses in the mutually agreed deal, including those already received. The government had originally ordered 90 million doses from the company.
No cancellation fee would be charged and the government said the new arrangement represented "fair value" and "significant savings", but released no further comment on the difference between the doses received and the cut in payment.
An undefined amount of the H5N1 bird-flu vaccine and courses of Glaxo's antiviral treatment Relenza are also included in the new deal.
The Department of Health said while it had initially ordered enough of Glaxo's Pandemrix vaccine for the whole population, further evidence on swine flu had persuaded experts that total vaccination was unnecessary. The cap on the vaccine doses to be received from Glaxo represents stock that had already been produced for the UK and "could not reasonably retract".