Exploring the role of mass immunisation in influenza pandemic preparedness: a modelling study for the UK context

Existing modelling work on preparedness to pandemic influenza has focused on evaluating specific countermeasures for pandemics with specific characteristics (typically based on historical instances). The aim of this study was to inform policy on preparedness planning for pandemic influenza based on the assessment of a wide range of scenarios and free from restrictive assumptions about timing and features of the next pandemic.\n\nWe carried out epidemiological modelling and health economic analysis of an extensive set of scenarios, each comprising a combination of pandemic, vaccine and immunisation programme characteristics in presence or absence of access to effective antivirals. Preparedness policies that incorporate mass immunisation were evaluated on the basis of there being a given chance of a pandemic each year. To support understanding and exploration of model output, an interactive visualisation tool was devised and made available online.\n\nWe evaluated over 29 million combinations of pandemic and policy characteristics. Preparedness plans incorporating mass immunisation show positive net present value for a wide range of pandemic scenarios, predominantly in the absence of effective antivirals. Plans based on the responsive purchase of vaccine have greater benefit than plans reliant on the purchase and maintenance of a stockpile if immunisation can start without extensive delays. This finding is not dependent on responsively purchased vaccine being more effective than stockpiled vaccine, but rather is driven by avoiding the costs of storing and replenishing a stockpile.\n\nWhile emerging technologies for rapid vaccine development and production increase the prospects for mass immunisation to be an effective countermeasure, policies based on the responsive purchase of vaccine not tailored to the pandemic should be explored. Focus is also required on the pandemic intelligence, decision, contractual and logistical processes on which timely commencement of immunisation in a pandemic is reliant.