Pneumococcal vaccine is prepared by purifying polysaccharides (sugars) from the capsules of the most common types of Streptococcus pneumoniae causing human illness. The mix of types is different for adults and children. The first pneumococcal vaccines, which were administrated in a single injection, consisted of only polysaccharides and did not reliably induce protection in infants and young children, nor did they induce immunologic memory. Consequently, protection (which was only partial) lasted only for a few years. In adults these vaccines provided 50 to 80 percent protection against severe pneumococcal disease. They were recommended for all persons sixty-five years of age or older and for younger persons with medical conditions that put them at increased risk of pneumococcal disease (such as chronic cardiovascular or pulmonary disease, diabetes mellitus, and alcoholism). Newer vaccines are prepared by conjugating the polysaccharides with some protein to induce immunologic memory and provide protection to infants as well as adults. They are administrated in a series of three injections at intervals of approximately two months. Approximately 90 percent of infants who receive the vaccine are protected from systemic disease caused by the types of pneumococci contained in the vaccine. Duration of protection and the possible need for booster doses has not yet been established. No serious adverse effects have been shown to be caused by either formulation of pneumococcal vaccine.
Centers for Disease Control and Prevention (1997). "Prevention of Pneumococcal Disease: Recommendations of the Advisory Committee on Immunization Practices (ACIP)." Morbidity and Mortality Weekly Report 46:1–23.
ALAN R. HINMAN, The Gale Group Inc., Macmillan Reference USA, New York,