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.