SEROGROUP-SPECIFIC EPIDEMIOLOGY OF STREPTOCOCCUS-PNEUMONIAE - ASSOCIATIONS WITH AGE, SEX, AND GEOGRAPHY IN 7,000 EPISODES OF INVASIVE DISEASE

A study sample of 7,010 episodes of invasive Streptococcus pneumoniae disease was obtained by combining 13 existing datasets. Disease episod es due to each of 12 pneumococcal serogroups (1, 3-9, 14, 18, 19, and 23) were then compared with episodes in a constant internal control gr oup to describe serogroup-specific variations in disease frequency by age, sex, and geographic origin. The results are presented as odds rat ios (with 95%, confidence intervals) derived by logistic regression, w ith adjustment for the major confounders, including dataset of origin. Variation in the male:female ratios between serogroups is small, sugg esting that capsular characteristics are an unlikely explanation for t he male preference of S. pneumoniae. Serogroups associated with higher nasopharyngeal prevalence (e.g., 19 and 23) are relatively more commo n in Europe and North America, while the invasive serotypes 1 and 5 ar e much more common in South America. The custom of reporting serogroup frequencies in two age groups, children and adults, conceals much of the variation in the age distributions across the whole span of life. The reduction of risk associated with serogroups 6, 14, 18, 19, and 23 beyond childhood follows different gradients, being most abrupt in se rotype 14 and most gradual in serogroup 18. The relative risk of disea se with serotype 1 declines steadily throughout life, while with serot ypes 3 and 8 it increases over middle age. Serogroups 7 and 23 are fou nd unusually frequently in the third decade of life. Because of the wi de differences in the epidemiology of individual serogroups of S. pneu moniae, it is questionable whether pneumococcal infection should conti nue to be classified as a single disease entity.