Abstract
Streptococcus pneumoniae infection is a common and serious health problem that is best prevented by the pneumococcal vaccine. The first vaccine approved by the U.S. Federal Drug Administration in 1977 contained 14 polysaccharide antigens. An improved vaccine introduced in 1983 included 23 polysaccharide antigens. Both vaccines were effective for immunocompetent adults; however, young children and immunocompromised adults remained susceptible. A pediatric vaccine was developed consisting of the capsular antigens of seven pneumococcal serotypes commonly found in children. The antigens in this preparation are covalently conjugated to diphtheria protein to make them more antigenic. The conjugate vaccine was expanded to include 13 serotypes by 2010. Although more immunogenic, the conjugate vaccine has fewer serotypes than the older 23-valent vaccine. The U.S. Centers for Disease Control and Prevention recommend that children at risk for pneumococcal pneumonia as defined by the presence of chronic disease should receive the 13-valent conjugated vaccine. Adults at risk for pneumococcal pneumonia, which includes those over 65 years of age and those who have a chronic disease, should receive the 23-polysaccharide vaccine. Immunosuppressed patients of any age should receive both vaccines. Adults should be revaccinated once at age 65 years or older with the 23-polysaccharide vaccine provided that at least 5 years have elapsed since the previous vaccination.