Changing Characteristics of Invasive Pneumococcal Disease in Metropolitan Atlanta, Georgia, after Introduction of a 7-Valent Pneumococcal Conjugate Vaccine

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Abstract
Background. The rate of invasive pneumococcal disease (IPD) has decreased among both immunized children and nonimmunized adults since the licensure of a heptavalent pneumococcal conjugate vaccine (PCV7) for use in infants in the United States in 2000. Methods. Temporal trends in IPD incidence, clinical syndromes, and underlying conditions were analyzed using active laboratory- and population-based surveillance data from the Centers for Disease Control and Prevention-sponsored Georgia Emerging Infections Program for the 20-county Metropolitan Atlanta, Georgia, for the period of July 1997 through June 2004. P values were determined by test for trend. Results. Since 2000, there have been significant decreases in the rates of invasive pneumococcal pneumonia (relative risk [RR], 0.80; P = .002) and meningitis (RR, 0.41; P = .003) in adults and for primary bacteremia, invasive pneumonia, and meningitis in children (RR, 0.16 [P < .001], 0.60 [P = .003], and 0.70 [P = .009], respectively). Among human immunodeficiency virus-infected persons, there were significant decreases in the overall rates of IPD (decrease of 43%; P < .001) and invasive pneumonia (decrease of 44%; P < .001) since 2000–2001, although the rate of IPD increased significantly (increase of 53%; P = .022) among patients with acquired immunodeficiency syndrome. There was a concurrent increase in the proportion of adults aged ⩾40 years with underlying comorbidities. Rates of non-PCV7 serotypes increased 1.61-fold and 1.28-fold from 2000–2001 to 2003–2004 in children and adults (P = .005 for both). Conclusions. The decreasing incidence of IPD in Atlanta since 2000–2001 was associated with decreases in cases of pneumonia and meningitis in adult and pediatric subjects and in cases of primary bacteremia in children. The burden of serotype-replacement disease remained small. Adults with comorbidities represent a growing proportion of patients with IPD.