Disease transmission models are being increasingly used to analyse the effectiveness and cost-effectiveness of alternative mitigation strategies. Key modelling principles will be presented together with an overview of recent modelling research conducted at the University of Western Australia with international partners.
A modelling study was conducted to determine the effectiveness of trivalent (TIV) and quadrivalent (QIV) influenza vaccination in Australia and South Africa. This study determined the potential benefits arising from alternative influenza vaccination strategies and how the magnitude of these benefits depend upon the influenza strain circulation, demographics and specific health characteristics of each setting. Seasonal influenza spread and the effect of influenza vaccination were simulated using two individual-based simulation models representing specific communities: Albany, Australia and Agincourt, South Africa, over a period of 11 influenza seasons (2003-2013). Two influenza A and two influenza B co-circulating strains had their transmissibility modelled to match surveillance-derived strain ratios occurring each year in each country. Scenarios using TIV or QIV, with alternative prioritisation strategies and vaccine coverage levels were evaluated. A health outcomes process specific to each country was then applied to estimate numbers of cases, hospitalisations and deaths prevented using each vaccination strategy.
A spatially-explicit, individual-based mathematical model that accounts for the spread of dengue infection as a result of human movement and mosquito dispersion will also be presented. The model closely couples the four key sub-models necessary for representing the overall dynamics of the physical system, namely those describing mosquito population dynamics, human movement, virus transmission and vector control. The model has been calibrated using detailed dengue outbreak data from Cairns (from 2003), together with census and mosquito trapping data, and is shown to realistically reproduce a further dengue outbreak. The simulation results replicating the 2008/2009 Cairns epidemic helps explain the large-scale epidemic which occurred; while warmer weather and increased human movement had only a small effect on the spread of the virus, a shorter virus strain-specific extrinsic incubation time can explain the observed explosive outbreak.
Dengue vaccination strategies over a 30 year time period have recently been analysed using an endemic dengue Thailand model and initial results from this study will be presented.