Potential impact of conjugate pneumococcal vaccines on pediatric pneumococcal diseases.

Children younger than age 2 years have the highest rates of invasive pneumococcal disease and play an important role in its transmission. In the United States, seven pneumococcal serotypes cause approximately 80% of invasive disease and represent approximately 60% of middle-ear isolates in children younger than age 2 years; the majority of penicillin-resistant strains are confined to these same few serogroups. Although unconjugated polysaccharide pneumococcal vaccines have demonstrated effectiveness in preventing invasive disease in adults, these vaccines fail to protect against otitis media or nasopharyngeal carriage and are poorly immunogenic in children younger than age 2 years. A new generation of pneumococcal vaccines has been developed, linking the capsular polysaccharide of seven to 11 serotypes to a protein carrier. The only pneumococcal vaccine approved to date for children younger than age 2 years is a seven-valent conjugate vaccine (PnCRM-7) (Prevnar; Wyeth Vaccines, Pearl River, New York), which contains serotypes 4, 6B, 9V, 14, 18C, 19F, and 23F. PnCRM-7 is more immunogenic than the polysaccharide pneumococcal vaccines and is 80-100% effective against vaccine-type invasive disease and 50-60% effective against vaccine-type pneumococcal otitis media. Routine immunization with pneumococcal conjugate vaccines should substantially reduce the morbidity, mortality, and costs associated with pneumococcal disease in children.