Assessing dengue vaccination impact: Model challenges and future directions.

In response to the sharp rise in the global burden caused by dengue virus (DENV) over the last few decades, the WHO has set out three specific key objectives in its disease control strategy: (i) to estimate the true burden of dengue by 2015; (ii) a reduction in dengue mortality by at least 50% by 2020 (used as a baseline); and (iii) a reduction in dengue morbidity by at least 25% by 2020. Although various elements will all play crucial parts in achieving this goal, from diagnosis and case management to integrated surveillance and outbreak response, sustainable vector control, vaccine implementation and finally operational and implementation research, it seems clear that new tools (e.g. a safe and effective vaccine and/or effective vector control) are key to success. The first dengue vaccine was licensed in December 2015, Dengvaxia® (CYD-TDV) developed by Sanofi Pasteur. The WHO has provided guidance on the use of CYD-TDV in endemic countries, for which there are a variety of considerations beyond the risk-benefit evaluation done by regulatory authorities, including public health impact and cost-effectiveness. Population-level vaccine impact and economic and financial aspects are two issues that can potentially be considered by means of mathematical modelling, especially for new products for which empirical data are still lacking. In December 2014 a meeting was convened by the WHO in order to revisit the current status of dengue transmission models and their utility for public health decision-making. Here, we report on the main points of discussion and the conclusions of this meeting, as well as next steps for maximising the use of mathematical models for vaccine decision-making

Celebrating HICSS50: The Past, Present, and Future of HICSS

The Hawaii International Conference on System Sciences (HICSS) celebrated its 50th anniversary (HICSS-50) in January, 2017. To mark the occasion and to pay respect to the significant standing of this conference in the global IS community, the Communications of the Association for Information Systems (CAIS) organized a special section on “Celebrating HICSS50: The Past, Present, and Future of HICSS Conference”. In this editorial, we share the guest editors’ perspectives on HICSS and summarize the three papers in the special section

Analysis of symmetries in models of multi-strain infections

In mathematical studies of the dynamics of multi-strain diseases caused by antigenically diverse pathogens, there is a substantial interest in analytical insights. Using the example of a generic model of multi-strain diseases with cross-immunity between strains, we show that a significant understanding of the stability of steady states and possible dynamical behaviours can be achieved when the symmetry of interactions between strains is taken into account. Techniques of equivariant bifurcation theory allow one to identify the type of possible symmetry-breaking Hopf bifurcation, as well as to classify different periodic solutions in terms of their spatial and temporal symmetries. The approach is also illustrated on other models of multi-strain diseases, where the same methodology provides a systematic understanding of bifurcation scenarios and periodic behaviours. The results of the analysis are quite generic, and have wider implications for understanding the dynamics of a large class of models of multi-strain diseases

Grain size prediction during open die forging processes

One of the most important target parameters during open die forging is the microstructure, respectivelythe grain size. This paper details different semi-empiric models that ultimately help to predict the microstructureproperties of a forged block. As a first step, trials in industrial scale were performed by Buderus EdelstahlGmbH and attended by SMS Meer GmbH. The collected process data was used by the Institute of Metal Forming(IBF) for the numerical analysis of the open die forging process and to validate the microstructure predictionmodule STRUCSIM. The numerical prediction of the grain size shows a good agreement with the resultsobtained from the metallography. In a second step models for the core fibre of a forged block were developedat the IBF. The models use data from the online process measurement and simplified plastomechanicalinterrelations for the calculation of equivalent strain and the temperature in the core of the forged part duringthe process. With their results the microstructure in the core fibre of the workpiece can be predicted online.The models are still in development and the most recent results will be presented in this paper

Canalization of the evolutionary trajectory of the human influenza virus

Since its emergence in 1968, influenza A (H3N2) has evolved extensively in genotype and antigenic phenotype. Antigenic evolution occurs in the context of a two-dimensional 'antigenic map', while genetic evolution shows a characteristic ladder-like genealogical tree. Here, we use a large-scale individual-based model to show that evolution in a Euclidean antigenic space provides a remarkable correspondence between model behavior and the epidemiological, antigenic, genealogical and geographic patterns observed in influenza virus. We find that evolution away from existing human immunity results in rapid population turnover in the influenza virus and that this population turnover occurs primarily along a single antigenic axis. Thus, selective dynamics induce a canalized evolutionary trajectory, in which the evolutionary fate of the influenza population is surprisingly repeatable and hence, in theory, predictable.Comment: 29 pages, 5 figures, 10 supporting figure