Table 1.

Key events, official risk assessments and UK policy decisions during study period

Date (2009)	Event/policy decision
Week of 20 April	First human cases of H1N1 confirmed in Mexico, the USA and Canada.
24 April	HPA press release: “The mild illness reported to date and the limited evidence of sustained human-to-human transmission suggest that the immediate level of threat to public health is very limited”.
26 April	UK government agrees to containment measures as part of its emergency response, including treatment of suspected cases and their close contacts with neuraminidase inhibitors without waiting for diagnostic confirmation.
27 April	Confirmation of first UK cases. Minister of Health issues statement: “The range of symptoms in the people affected is similar to those of regular human seasonal influenza. It is important to note that, apart from in Mexico, all those infected with the virus have experienced mild symptoms and made a full recovery”.
29 April	WHO states, “It is possible that the full clinical spectrum of this disease goes from mild illness to severe disease. We need to continue to monitor the evolution of the situation...”. UK government decides to increase the national stockpile of neuraminidase inhibitors from 33.5 million to 50 million doses.
1 May	HPA confirms human-to-human transmission in UK, stating: “At this stage, we still only have two cases of human to human transmission in the UK. This does not yet represent sustained human to human transmission. The risk to the general public is still very low”.
11 May	UK government takes decision to purchase sufficient H1N1-specific vaccine for 45% of the population.
11 June	WHO confirms start of a global pandemic, stating “we have good reason to believe that this pandemic, at least in its early days, will be of moderate severity. Worldwide, the number of deaths is small. [..]..we do not expect to see a sudden and dramatic jump in the number of severe or fatal infections”.
15 June	DH statement: “The localised cases of swine flu found in the UK have so far been generally mild in most people, but are proving to be severe in a small minority of cases”.
17 June	WHO welcomes donation by Sanofi-Aventis of 100 million doses of H1N1 vaccine for low-income countries.
26 June	GlaxoSmithKline and Baxter Healthcare contracted to provide a total of 132 million doses of H1N1-specific vaccine, sufficient for two doses for the whole UK population.
2 July	UK government changes to ‘treatment’ phase in its emergency response, where prophylaxis with neuraminidase inhibitors would be provided to those in high-risk groups only. HPA press release states: “Once the virus is widespread within the community, the value of antivirals in terms of slowing the spread of the disease or offering individual protection is greatly reduced”.

DH, Department of Health (England); HPA, Health Protection Agency.