EPIDEMIOLOGIC STUDIES OF STREPTOCOCCUS PNEUMONIAE IN INFANTS

Abstract

In a study of the natural history of pneumococcai carriage and infection in infants enrolled at birth in Birmingham, Alabama from November 1974 to December 1975, the authors observed patterns of acquisition and carriage that appeared to be influenced by age and the season of the year. To describe more precisely these effects, the original data were used to construct muttiple regression models for acquisition, carriage rates, and duration of carriage of pneumfxocci during the first 24 months of life. The acquisition rate was strongly seasonal, with a marked winter peak and summer low. Seasonal fluctuations in the carriage rate were much less pronounced. The acquisition rate increased with age, while the duratlon of carriage decreased; these cornbined effects were reflected in the carriage rate, which increased sharply up to the age of nine months, then leveled off. While age and season accounted for a relatively small part of the variation in acquisition and carrlage rates, the models were found to fit the data very well. The authors were able to analyze the data in a precise fashion, confirm earlier observations, and relate them to the work of other investigators over the past 50 years.