Changes in occurrence of capsular serotypes of Streptococcus pneumoniae at Boston City Hospital during selected years between 1935 and 1974.

The number of patients with pneumococcal bacteremia, empyema, and meningitis at Boston City Hospital during selected years between 1935 and 1974 is reported. The distribution of specific types in the bacteremic patients during each of the selected years and in the various focal infections in all the years is also detailed. The numbers and rates per 1,000 admissions of bacteremic pneumococcal infections and the numbers of cases of pneumococcal meningitis and empyema varied independently over these years and differed from those previously reported for 1929 to 1936. The types most frequent in pneumococcal bacteremias varied over the years, and the distribution of types among them differed markedly from that among the patients with focal infections. Variations in the distribution of pneumococcal types at different times in the same place, in different places, and in various sites of infection may be important in selecting types to include in pneumococcal vaccines for different populations.