What do you do with vaccine that no-one needs?
That is the question currently puzzling the Department of Health. Back in May the government signed contracts with two suppliers - GSK and Baxter - to supply 90 million doses of H1N1 pandemic vaccine.
That was on the basis that two doses would be needed to provide protection. Swine flu has turned out to be far milder than was initially feared and so the government is going to be left with a huge amount of unused vaccine.
The Department of Health has revealed that it has a break clause in its contract with Baxter which had been asked to supply 30 million doses, but it appears there is no get-out clause in the deal with GSK, set to provide 60 million doses. GSK has so far delivered 23.9 million doses to the government and Baxter five million.
That is more than enough to vaccinate all the at-risk groups and the government made clear there are no plans to extend immunisation.
The Head of Immunisation at the Department of Health, Professor David Salisbury said: "The Baxter contract has a break clause. We are in discussion with GSK about future supplies of vaccine." When asked how much the government might be able to re-coup from the deal with GSK he said "That is what we are discussing now."
For commercial reasons no figure has been given for the cost of the vaccine contracts, but it's likely to run into several hundred million pounds. Professor Salisbury said there were a number of options which included selling excess doses or giving them away to developing countries.
But he added that it was essential that the UK kept a stockpile of H1N1 vaccine in case there was a resurgence of the virus over the coming year.
One option being discussed with GSK, which was described as "innovative" by the Chief Medical Officer Sir Liam Donaldson, would involve keeping a stockpile of adjuvant, the booster chemical which is produced separately from the vaccine and mixed later.
Professor Salisbury said this would be a good idea as it could be used in conjunction with another flu vaccine in the event of a new pandemic. He said the adjuvant had a shelf life of five years.
When asked whether the NHS would be left substantially out of pocket by purchasing so much H1N1 vaccine, Sir Liam said that the contracts were signed earlier this year amid the early and very alarming information about deaths from the virus in Mexico. The death rates in Mexico were later reduced.
There are no accurate figures for the UK. But in England:
• At least one in three people in the initial priority groups has had the vaccine.
• 3.2 million doses have been administered.
• 113,000 pregnant women have had the jab out of around 600,000 - about one in five.
• 373,000 front-line health workers have had the jab out of around a million (there are no figures for uptake among front-line social care workers).
• 86,000 doses have been given to healthy children aged six months to under five out of more than three million, but this process only got underway before Christmas.
Professor Salisbury urged all those in the at-risk groups to get immunised, especially children under five because it was not clear what would happen with swine flu over the year ahead.
Swine flu figures
There is very little swine flu about. Latest figures show that there were fewer than 5,000 new cases in England over the past week. And disease "modellers" have advised the Department that a third wave of swine flu is unlikely this winter.
Sir Liam pointed out that there were the same experts who predicted that up to 65,000 people might die from swine flu this winter - a figure which was later downgraded to 1,000.
This lack of swine flu in the community will make it more difficult to persuade those at risk of flu complications to come forward to be immunised.
But the Chief Medical Officer Sir Liam Donaldson pointed out that 20 children under five and 12 pregnant women had died in the UK from swine flu related conditions since April.
To date there have been 360 deaths from swine flu in the UK (251 in England, 64 in Scotland, 28 in Wales and 17 in Northern Ireland). But the vast majority of those infected have had either a mild disease or no symptoms at all.
In England there were 393 people in hospital with swine flu on 6 January, 103 of them in critical care.