Prevention of pneumococcal infection by immunization with capsular polysaccharides of Streptococcus pneumoniae: current status of polyvalent vaccines.

Because of the continuing morbidity and mortality resulting from pneumococcal infection, a program was instituted to redevelop polyvalent vaccines consisting of capsular polysaccharides of Streptococcus pneumoniae. Vaccines containing 50 microgram each of the capsular polysaccharides of as many as 13 pneumococcal types have been shown to be safe, antigenic, and 78.5% effective in the prevention of type-specific putative pneumococcal pneumonia and of type-specific pneumococcal bacteremia in adults. In a population in which pneumococcal pneumonia predominated, the total incidence of radiologically confirmed pneumonia, irrespective of cause, was reduced by 54.3% by use of a tridecavalent vaccine. The efficacy of vaccine in the prevention of infection during the first two years of life is under investigation. The vaccine is recommended for those at high risk of pneumococcal infection or of a fatal outcome from such illness.