Incidence of Pneumococcal Disease Due to Non–Pneumococcal Conjugate Vaccine (PCV7) Serotypes in the United States during the Era of Widespread PCV7 Vaccination, 1998–2004

TLDR

PCV7 vaccination has lowered invasive pneumococcal disease overall, but may be counterbalanced by rising disease from serotypes not covered by the vaccine. The study aimed to assess how PCV7 affected incidence of nonvaccine serotype disease and to underscore the need for continued surveillance to guide future vaccine composition. Researchers analyzed invasive disease cases from CDC’s Active Bacterial Core surveillance in eight U.S. regions, performed serotyping and susceptibility testing, and calculated age‑specific incidence rates for children under five and adults 65 and older before and after PCV7 licensure.

Abstract

Widespread use of pneumococcal conjugate vaccine (PCV7) resulted in decreases in invasive disease among children and elderly persons. The benefits may be offset by increases in disease due to serotypes not included in the vaccine (hereafter, "nonvaccine serotypes"). We evaluated the effect of PCV7 on incidence of disease due to nonvaccine serotypes.Cases of invasive disease were identified in 8 geographic areas through the Centers for Disease Control and Prevention's Active Bacterial Core surveillance. Serotyping and susceptibility testing of isolates were performed. We calculated the incidence of disease for children aged <5 years and adults aged > or =65 years. We compared rates of serotype-specific disease before and after PCV7 was licensed for use.The annual incidence of disease due to nonvaccine serotypes increased from an average of 16.3 cases/100,000 population during prevaccine years (1998-1999) to 19.9 cases/100,000 population in 2004 for children aged <5 years (P=.01) and from 27.0 cases/100,000 population during prevaccine years to 29.8 cases/100,000 population in 2004 for adults aged > or =65 years (P=.05). Significant increases in the incidences of disease due to serotypes 3, 15, 19A, 22F, and 33F were observed among children during this period (P<.05 for each serotype); serotype 19A has become the predominant cause of invasive disease in children. The incidence of disease due to these serotypes also increased among elderly persons.The incidence of pneumococcal disease caused by nonvaccine serotypes is increasing. Ongoing surveillance is needed to monitor the magnitude of disease caused by nonvaccine serotypes, to ensure that future vaccines target the appropriate serotypes.