Improving Public Health Policy in Europe through Modelling and Economic Evaluation of Interventions for the Control of Infectious Diseases
The aim of POLYMOD is to strengthen public health decision-making in Europe through the development, standardisation and application of mathematical, risk assessment and economic models of infectious diseases. There are four issues that are addressed by this project. The first is that mathematical models are only as good as the assumptions and parameters on which they are built.
Patterns of mixing are central determinants of the transmission of many infections. However, little is known about contemporary mixing patterns. POLYMOD has therefore surveyed, for the first time, epidemiologically relevant contact patterns from representative samples of eight difference European countries. These internationally important datasets have been supplemented by other information sources, including serological data from a number of different countries.
New techniques have been developed to analyse these data, and they are already proving invaluable in helping improve our understanding of transmission mechanisms and helping improve mathematical models. Predicting the impact of control programmes against infectious diseases requires the use of sophisticated transmission dynamic models, as, due to the infectious nature of the organism, interventions often have knock-on effects beyond those that were directly targeted.
POLYMOD has adapted and developed such models, based on the contact pattern data, to address a number of public health issues, such as the impact that vaccination against varicella may have on the epidemiology of varicella zoster virus-related disease. In addition, novel techniques for assessing dose-response relationships and estimating incidence for use in risk assessments of gastrointestinal pathogens have been developed.
The results from models are being combined with cost and outcome data in a series of economic analyses to assess the cost-effectiveness of different vaccination programmes in Europe. Finally, the results are being presented to policymakers with the aim of helping improve public health decision-making.[+] Read More
Mathematical models are increasingly used to estimate the impact of control programmes against infectious diseases. The accuracy of model predictions depends on the quality of the data used to parameterise them. Contact patterns between individuals are critical to the spread of many infectious diseases (e.g. as influenza, TB, smallpox, meningitis etc). However, very little is known about the relevant contact patterns. Instead, analysts have assumed certain contact patterns based on very little (or no) data. Clearly, this affects the reliability of predictions and the policy advice that follows from this.
POLYMOD aims to collect relevant contact pattern data, improve mathematical models, use these models in economic analysis, and then convey the results to policymakers.
To improve public health decision-making, through improved mathematical models of the spread of infectious diseases.
Highlights of the results are presented here.
Figure 1. Age-specific contact matrices for different European countries. White colour indicates high contact rates, green intermediate contact rates and blue colour indicates low contact rates, relative to the countryspecific contact intensity. Data were presented in Mossong et al., PLoS Medicine, 2008.
Figure 1 summarises the age-dependency in contact patterns observed in the eight different countries that performed a survey. It is clear that contact patterns tend to be highly correlated with respect to age (people tend to contact others that are similar in age to themselves) and that this is particularly true for children and young adults. This has particularly important implications for vaccination programmes, which are often targeted at one age group, but may have an impact on other ages. Furthermore, it is very important for understanding the spread of emerging pathogens, such as pandemic influenza, and the potential impact of various control measures, including school closure. It is also very noticeable that contact patterns are similar in different European countries, suggesting that it may be able to extrapolate from these surveys to other countries. Full details of the results are given in Mossong et al. 'Social contacts and mixing patterns relevant to the spread of infectious diseases', PLoS Med, 2008, Mar 25;5(3):e71.
Utilising these contact patterns new models of VZV transmission have been developed and have been used to predict the impact of vaccination. The results of these models are being fed into economic analyses, and are being presented to decision-makers.
Figure 2. The estimated cost-effectiveness of rotavirus vaccination in 5 different European countries (data from Jit et al. unpublished).
Figure 2 gives an example of the costeffectiveness of rotavirus vaccination in a number of different countries (Jit et al., unpublished). The results suggest that rotavirus vaccination may not be cost-effective at current vaccine prices.
POLYMOD should lead to improved decisionmaking in the area of infectious disease control. The results generated are directly applicable to a wide range of diseases, including gastrointestinal diseases, vaccine-preventable diseases, and emerging infectious diseases, such as pandemic influenza.