Prevention of Pneumococcal Pneumonia by Immunization with Specific Capsular Polysaccharides

1. Immunization of man with 0.03 to 0.06 mg. of each of the capsular polysaccharides of pneumococcus types I, II, V, and VII, given in a single subcutaneous injection, has been shown to be effective in preventing pneumonia caused by these types but not that due to heterologous types. 2. Immunity appears within a period of 2 weeks following injection of the polysaccharides. Its duration was not determined, although 6 months can be set as a minimum. 3. Immunization of alternate subjects in the population reduced greatly the incidence of pneumonia in the non-immunized. 4. The carrier rate for pneumococcus types I, II, V, and VII was lowered significantly in the immunized group as compared with the controls. It is suggested that an over-all reduction in the incidence of carriers was responsible for the lowered rates for pneumococcal pneumonia in the non-immunized group.