Pneumococcal Capsular Polysaccharide Vaccine

Streptococcus pneumoniae (pneumococcus [Pnc]) is a common bacterial agent found in mild mucosal as well as severe systemic infections. Local infections, such as acute otitis media, are rather common; every child has at least one during the first 2 years of life (1), and Pnc is the causative agent in approximately half of the bacterial culturepositive cases (2). Pneumonia is another disease often caused by Pnc, both in industrialized and developing countries. Pneumonia, which causes more than one million deaths per year, is the most common cause of childhood death in the developing world (3); pneumococcal pneumonia is a serious problem among the elderly in industrialized countries. Pnc also causes frequent invasive infections, especially among children. In Finland, the incidence of bacteremic pneumococcal infections at 0 to 4 years of age has been 24.2 per 100,000 per year (4). The corresponding rate was 42 per 100,000 per year in Israel (5) and 66 per 100,000 per year in the United States (6). In addition to the young and the elderly, some of the other groups at increased risk for Pnc infection are patients with chronic cardiac or pulmonary diseases, immunocompromised patients, and especially persons with functional or anatomic asplenia (7). The treatment of recently emerged Pnc strains that are resistant to penicillin and other antibiotics (8) is becoming a challenge. Because of the high rates of illness and death associated with pneumococcal infections and the rapidly increasing resistance of organisms that cause these infections to antimicrobial drugs, development and use of effective pneumococcal vaccines is of high priority. The progress has been rapid; in addition to polysaccharide(PS)-protein conjugate vaccines, vaccines containing pneumococcal proteins are also being developed.