Streptococcus pneumoniae (the pneumococcus) is the leading cause of community-acquired pneumonia (CAP) and otitis media, and a primary cause of bacteremia and meningitis (Pneumococcal vaccines 1999). As with most infectious diseases, the poorest nations experience the greatest burden of disease. This can be attributed to reduced vaccine use, decreased standards of living, and limited access to supportive critical care (Dopazo et al. 2001; Robinson et al. 2001). Worldwide, the incidence of invasive pneumococcal disease (IPD) is greatest in children. However, death, as a result of infection, primarily occurs in the elderly (>65 years of age) (Atkinson et al. 2007; Lexau et al. 2005). The World Health Organization (WHO) estimates that pneumococcal disease is responsible for 1.6 million deaths annually (Pneumococcal vaccines 1999). Pneumococcal disease in the elderly is characterized by its rapid onset, severity, and high case-fatality rate; in the United States, the mortality rate for the elderly with pneumococcal pneumonia is 13-23%, compared to 5-7% in the general population. Likewise, case-fatality rates for the elderly with pneumococcal bacteremia and meningitis are 60% and 80%, respectively; in contrast, they are 20% and 30% for the general population (Atkinson et al. 2007). Risk factors for IPD include advanced age, alcoholism, bronchial asthma, immunosuppression, lung disease, heart disease, asplenia, diabetes, and institutionalization (Loeb 2004; Mufson 1999). It is of note that the majority of the elderly have one or more underlying medical conditions that puts them at increased risk for IPD (Robinson et al. 2001). Moreover, the elderly experience agerelated changes in immune function that increase their susceptibility to infection.
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