| Infections caused by Streptococcus pneumoniae, or the pneumococcus, have long been the topic of research, and yet are still today a significant cause of morbidity and mortality. Primarily afflicting the young in developing countries and the elderly in more developed regions, the vaccination of these diseases in age-structured populations poses unique challenges. Recent advances in the development of childhood vaccines raise questions concerning their potential impact if implemented widely and/or over a long period of time. In this work, general pneumococcal vaccination is incorporated in unstructured and age-structured population models of pneumococcal infections and the potential consequences of immunization programs are discussed. It is demonstrated here that only vaccines which intervene in the colonization of individuals have possible implications for disease eradication, as opposed to the currently available alternatives which target only progression to infection. With the age-structured model, the protective effects of targeting this stage are shown to be far-reaching and results in a significant reduction in disease morbidity in all age groups. These results and others suggest a shift in the focus of pneumococcal vaccine development. Further, surveillance data from Australia is used to calibrate a model to this population by estimating parameters commonly of interest to the research community that are either not available or not measurable. This calibrated model is used to assess the impact of a newly implemented vaccine, suggesting that changes in the picture of pneumococcal diseases are occurring in response to the program, making a case for close quantitative surveillance of these dynamics by public officials, The collection and analysis of age-stratified surveillance data is discussed in conjunction with an age-structured model, With this analysis, the need for colonization data is demonstrated to estimate parameters which are not measurable but on which disease dynamics are highly dependent. In addition, the assessment of vaccine programs rely heavily on the direct record of vaccination status of individuals at all stages of infection. Along with other results, this discussion provides public health officials with effective tools to design and assess implemented vaccine strategies against pneumococcal infections. |
