In the spring of 2009, a novel strain of the H1N1 influenza virus, containing a never before witnessed combination of gene segments from human influenza, two forms of swine influenza, and avian influenza, 1 was declared a global pandemic. The UK Government had to decide whether to undertake, at a cost of £1.2 billion (USD 1.9 billion at the time, equivalent to 1 percent of that year’s health budget), an extensive set of preparatory measures, including the purchase of both antiviral medication and a novel vaccine in quantities sufficient to cover the entire UK population, or whether instead to take substantially less costly measures, which would involve having only a limited supply of these medicines and vaccines at hand.2 The possible.