Emergency department epidemiology of pneumococcal bacteremia in children since the institution of widespread PCV7 vaccination.

Background: The heptavalent pneumococcal conjugate vaccine (PCV7) has produced a shift in the epidemiology of invasive infections from Streptoccoccus pneumoniae.

Objective: Our aim was to determine the temporal changes in pneumococcal bacteremia (Streptococcus pneumoniae bacteremia [SPB]) in the emergency department (ED) since the introduction of PCV7.

Methods: This was a retrospective cohort study of children 0-18 years with SPB evaluated from 1998-2009 in a tertiary-care pediatric ED. The primary outcome was annual proportion of children with SPB from PCV7 serotypes (ie, 4, 6B, 9V, 14, 18C, 19F, and 23F) and nonvaccine serotypes (NVT). Rates of SPB (per 10,000 ED visits) were calculated. SPB was analyzed by time period: before October 2000 was considered "pre-PCV7," November 2000 to October 2003 was considered "peri-PCV7," and after November 2003 was "post-PCV7." Febrile young children (FYC) were defined as children age <36 months and fever without source.

Results: A total of 201 episodes of SPB occurred during the study, with a median age of 20.3 months (interquartile range 10.7-49.5 months; range 1.6-215.4 months); 56.7% were male and 69.7% were African American. SPB from PCV7 serotypes decreased more than fourfold, from 82.2% pre-PCV7 to 19.5% peri- and post-PCV7. Most SPB was from NVT serotype 19A (31.3%) peri- and post-PCV7. Annual rates of SPB were 4.01/10,000 ED visits pre-PCV7, decreasing to 2.10 peri-PCV7, and 1.75 post-PCV7. Among the 56 (27.8%) FYC with SPB, NVT were responsible for 11.5% of SPB pre-PCV7, and increased to 80.0% peri- and post-PCV7 (p < 0.001).

Conclusions: Rates of SPB have decreased since the introduction of PCV7, yet SPB still occurs among children in the ED. NVT are increasing in prevalence, and SPB from PCV7-serotypes have decreased.