 The World Health Organization WHO estimated that more than 800 000 children younger than 5 years died from pneumococcal disease in 2000, making it the leading vaccine-preventable cause of death. Pneumococcal polysaccharide vaccines have progressed from 2-valent vaccines to the current 23-valent vaccine, which has been available since the early 1980s. The 23-valent vaccine includes serotypes accounting for 72 to 95 of invasive pneumococcal disease, depending on the geographic area. Many countries have added pneumococcal polysaccharide vaccine to their existing national immunization programs or recommended it for people aged 65 years and older and for individuals aged 2-64 who are at increased risk of pneumococcal disease. 