Abstract
The purpose of this paper is to report on work done since 1937 on active immunization with antigenic polysaccharides against pneumonia. The group immunized were inmates of the New York City Home. Most of them were above the age of 50 and a great majority between the ages of 60 and 80 (table 1). There were several reasons why this group was chosen for the experiment. First: They have a high incidence of pneumonia, mortality and case fatality rate. Second: Repeated attacks of pneumonia occur frequently. Third: They could be kept under observation for years, as the turnover in the Home is limited and those who were discharged could be followed up; moreover a great many of them were readmitted to the Home and further observed. Fourth: Those who contracted pneumonia were transferred to the supervising hospital of the New York City Home for Dependents (which was previously the Central