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Changing Epidemiology of Outpatient Bacteremia in 3- to 36-Month-Old Children After the Introduction of the Heptavalent-Conjugated Pneumococcal Vaccine

Herz, Arnd M. MD*; Greenhow, Tara L. MD†; Alcantara, Jay*; Hansen, John BA‡; Baxter, Roger P. MD§; Black, Steve B. MD‡; Shinefield, Henry R. MD‡

Pediatric Infectious Disease Journal: April 2006 - Volume 25 - Issue 4 - pp 293-300
doi: 10.1097/01.inf.0000207485.39112.bf
Original Studies

Background: The introduction of routine vaccination with heptavalent conjugated pneumococcal vaccine has changed the overall incidence of bacteremia in children 3 months–3 years old.

Objective: To describe the changing incidence and etiology of bacteremia in previously healthy toddlers presenting to outpatient clinical settings.

Methods: Retrospective case series of all blood cultures obtained between September 1998 and August 2003 in Kaiser Permanente Northern California outpatient clinics and emergency departments from previously healthy children 3 months–3 years old.

Results: Implementation of routine vaccination with the conjugated pneumococcal vaccine resulted in an 84% reduction of Streptococcus pneumoniae bacteremia (1.3–0.2%) and a 67% reduction in overall bacteremia (1.6–0.7%) in the study population. The rate of blood culture isolation of contaminating organisms remained unchanged at 1.8%; therefore, by the end of the study, >70% of organisms identified in blood cultures were contaminants. During the 5 study years, total blood cultures drawn decreased by 35% in outpatient pediatric clinics but remained unchanged in emergency departments. By 2003, one-third of all pathogenic organisms isolated from blood cultures were Escherichia coli, one-third were non-vaccine serotype S. pneumoniae, the majority of the remaining one-third were Staphylococcus aureus, Salmonella spp., Neisseria meningitidis and Streptococcus pyogenes. In our population of children routinely immunized with the conjugated pneumococcal vaccine, a white blood cell count >15,000 by itself is a poor predictor of bacteremia in the febrile toddler (sensitivity, 74.0%; specificity, 54.5%; positive predictive value, 1.5%; negative predictive value, 99.5%).

Conclusion: In the United States, routine vaccinations with Haemophilus influenzae type b and S. pneumoniae vaccines have made bacteremia in the previously healthy toddler a rare event. As the incidence of pneumococcal bacteremia has decreased, E. coli, Salmonella spp. and Staphylococcus aureus have increased in relative importance. The use of the white blood cell count alone to guide the empiric use of antibiotics is not indicated. New guidelines are needed to approach the previously healthy febrile toddler in the outpatient setting.

From the *Department of Pediatrics and Pediatric Infectious Disease, Kaiser Permanente, Hayward, CA; the †Department of Pediatric Infectious Disease, University of California San Francisco, San Francisco, CA; the ‡Vaccine Study Center, Kaiser Permanente, Oakland, CA; and the §Regional Laboratory, Kaiser Permanente, Berkeley, CA

Accepted for publication November 11, 2005.

Dr Baxter has received grants from GlaxoSmithKline, Sanofi Pasteur, Merck, Chiron, MedImmune, Wyeth and Bayer.

Address for reprints: Arnd M. Herz, MD, Chief of Pediatrics and Pediatric Infectious Disease, The Permanente Medical Group, 27400 Hesperian Boulevard, Hayward, CA 94545. Fax 510-784-4974; E-mail arnd.herz@kp.org.

© 2006 Lippincott Williams & Wilkins, Inc.