Association of Serotypes of Streptococcus pneumoniae with Age in Invasive Pneumococcal Disease

A total of 7,764 isolates from patients with invasive pneumococcal disease (IPD) were collected from 1992 to June 2006. Data on serotypes were available for 5,022 isolates (64.7% of all invasive isolates). Some 54.0% of the isolates originated from adults ≥16 years of age, and 46.0% were from children <16 years of age. The leading serotypes were 14, 23F, 1, 6B, 7F, 3, and 4. The serotypes significantly more common in children were 14, 6B, 19F, and 18C, while among adults, serotypes 3 and 4 were predominant. Serotype 7F was statistically more prevalent among children <4 months old than among the other age groups. Among children aged ≥4 months and <1 year, serotype 19F occurred statistically more frequently; and among children aged ≥1 year to <5 years, serotypes 14, 6B, and 18C were overrepresented. The serotypes predominantly affecting patients younger than the remaining collective of patients were 14, 6B, 19F, and 18C, while patients with IPD caused by serotypes 3, 4, and 9V were older than the collective, on average.Streptococcus pneumoniae is among the most important pathogens in bacterial pneumonia, sepsis, and meningitis worldwide (1). The capsular polysaccharide of S. pneumoniae is known to be an important factor in the pathogenicity of the organism (7), and associations of the capsular serotypes with the severity of invasive pneumococcal diseases (IPDs) have been described (2, 14). IPDs are known to be much more frequent among young children and elderly persons than among older children and middle-aged adults (25). The results of several studies of the frequencies of pneumococcal serotypes and pneumococcal vaccine coverage have been published, but only few data on the serotype distribution among children and adults or different age groups are available. Studies from the United States (10, 19, 25), Canada (18), England and Wales (21), and Denmark (9), as well as the available meta-analyses (4, 15), refer to a diversity of age intervals. Although some studies contain statistics on the serotypes covered by the seven-valent pneumococcal conjugate vaccine (PCV7) and those not covered by the vaccine, no information on the association of individual serotypes with age are given. Another meta-analysis reported on the relative risk (odds ratio) of IPD caused by the various serotypes among all age groups subdivided into 10-year bands (26). Furthermore, in a 19-year nationwide surveillance study from Denmark, statistical analyses of the serotype distribution with age have been performed, but that study included only children aged 0 to 6 years (16). Some statistical data about individual serotypes and their association with age can also be found in the report of a study from the United States on the increased prevalence of pediatric pneumococcal serotypes in elderly adults. However, the study contained data only for adults aged ≥35 years (5).The aim of the study described here was to evaluate the association of serotypes of S. pneumoniae with age in IPD among isolates from all age groups sent to the German National Reference Center for Streptococci (NRCS) between 1992 and 2006.