Infections caused by Streptococcus pneumoniae are a major cause of morbidity and mortality in the pediatric population worldwide. Development of increasing resistance to multiple classes of antibiotics is making treatment of infections caused by this organism much more difficult. In order to prevent disease, a 23-valent pneumococal polysaccharide vaccine is available. However, this vaccine is poorly immunogenic in infants and young children. The development and licensing of pneumococcal conjugate vaccines that are safe and effective in the pediatric population is an important step in our ability to decrease the prevalence of pneumococcal disease seen.