Mitigation Strategies for Pandemic Influenza A: Balancing Conflicting Policy Objectives

Abstract

Mitigation of a severe influenza pandemic can be achieved using a range of interventions to reduce transmission. Interventions can reduce the impact of an outbreak and buy time until vaccines are developed, but they may have high social and economic costs. The non-linear effect on the epidemic dynamics means that suitable strategies crucially depend on the precise aim of the intervention. National pandemic influenza plans rarely contain clear statements of policy objectives or prioritization of potentially conflicting aims, such as minimizing mortality (depending on the severity of a pandemic) or peak prevalence or limiting the socio-economic burden of contact-reducing interventions. We use epidemiological models of influenza A to investigate how contact-reducing interventions and availability of antiviral drugs or pre-pandemic vaccines contribute to achieving particular policy objectives. Our analyses show that the ideal strategy depends on the aim of an intervention and that the achievement of one policy objective may preclude success with others, e.g., constraining peak demand for public health resources may lengthen the duration of the epidemic and hence its economic and social impact. Constraining total case numbers can be achieved by a range of strategies, whereas strategies which additionally constrain peak demand for services require a more sophisticated intervention. If, for example, there are multiple objectives which must be achieved prior to the availability of a pandemic vaccine (i.e., a time-limited intervention), our analysis shows that interventions should be implemented several weeks into the epidemic, not at the very start. This observation is shown to be robust across a range of constraints and for uncertainty in estimates of both R0 and the timing of vaccine availability. These analyses highlight the need for more precise statements of policy objectives and their assumed consequences when planning and implementing strategies to mitigate the impact of an influenza pandemic.

The influence of school holiday timing on epidemic impact

“…In agreement with Hollingsworth et al [18] but in contrast to Glass & Barnes [9], we find that the greatest benefit is achieved when the holiday Figure 5, but with τ = 0·04, resulting in larger R 0 . In panel (b) the grey circles without borders denote that the peak week entirely takes place during the holidays.…”

“…vaccination, during those 6 weeks [18]. If the 2009 influenza pandemic experience is repeated [27], the prospect of having sufficient vaccine doses available to make an impact at the population level in such a time period is unlikely.…”

“…Numerous infectious disease outbreaks take place in schools, and it is expected that schools would feature heavily in any new epidemic of influenza and similar illnesses [1,[4][5][6]. Therefore school closure has been considered as a possibility during an outbreak [7][8][9][10][11][12][13][14][15][16][17][18][19]. There are a number of reasons why school closure might take place, including staff illness, high levels of pupil absence, parental concern, or as an intervention to attempt to slow the spread of infection.…”

A literature review to identify factors that determine policies for influenza vaccination

“…This information was generally provided by surveillance networks, virology laboratories, and national health institutes. By contrast, for pandemics, modelling had a greater impact [73][74][75]. Furthermore, new factors influenced the decision because of the limited data regarding the clinical and epidemiological aspects of pandemics and the ethical and logistical challenges, including public acceptability [33].…”

Should all children be immunised against influenza?

“…The path towards LAIV introduction in the UK has been little different in this respect, although it is clear that R 0 —the index of infectiousness which determines the level of vaccine coverage necessary to interrupt transmission—is perilously (for the virus) close to one for influenza 43. Accordingly, there are very good reasons to expect potent indirect effects of high coverage immunisation with an efficacious vaccine.…”