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Surveillance for Invasive Pneumococcal Disease During 2000–2005 in a Population of Children Who Received 7-Valent Pneumococcal Conjugate Vaccine

Black, Steven MD*; France, Eric K. MD; Isaacman, Daniel MD; Bracken, Laura§; Lewis, Edwin MPH§; Hansen, John BA§; Fireman, Bruce MA§; Austrian, Robert MD; Graepel, Jay PhD; Gray, Sharon MS; Klein, Nicola P. MD, PhD§

The Pediatric Infectious Disease Journal: September 2007 - Volume 26 - Issue 9 - p 771-777
doi: 10.1097/INF.0b013e318124a494
Original Studies

Objectives: To assess the incidence of invasive pneumococcal disease (IPD) in all children younger than 5 years of age in the Northern California Kaiser Permanente (NCKP) health care system during a 5-year surveillance period (2000–2005) after the introduction in April 2000 of routine use of 7-valent pneumococcal conjugate vaccine (PCV7).

Methods: This was a laboratory-based surveillance study of all children younger than 5 years of age in the NCKP health care system from April 2000 to March 2005. The comparison group was all children younger than 5 years of age in the NCKP health care system from April 1996 to March 2000. Data obtained from clinical databases included microbiologic identification and susceptibility testing; serotyping of isolates; immunization records; and IPD diagnoses for inpatients and outpatients. IPD was defined as a positive culture of Streptococcus pneumoniae from a normally sterile body site.

Results: For all serotypes, the mean annual incidence of IPD during the postlicensure surveillance period was 15.3 cases/100,000 person-years (105 p-y) compared with 62.5 cases/105 p-y in the prelicensure years of 1996–2000. The average incidence of IPD caused by vaccine serotypes was reduced from 50.1 cases/105 p-y during the prelicensure years to 4.9 cases/105 p-y during the postlicensure period. The average incidences of IPD caused by cross-reactive and by nonvaccine serotypes were 5.8 and 5.3 cases/105 p-y, respectively, during the prelicensure years and 2.5 and 6.2 cases/105 p-y, respectively, during the postlicensure period. Of the 131 IPD cases observed during the postlicensure surveillance period, bacteremia (50.4%) and pneumonia (31.3%) were the most common diagnoses. During the 5-year postlicensure surveillance period, only 3 subjects who were identified to be fully vaccinated for age with PCV7 (3 doses by 7 months of age or 4 doses by 18 months of age) developed vaccine-serotype IPD.

Conclusion: The incidence of IPD has significantly decreased in a large population of children after the introduction of PCV7. Vaccine-type IPD was rare in patients who received full 4-dose immunization with PCV7. There is no clear evidence of a significant increase in nonvaccine-serotype IPD. Introduction of a 4-dose infant schedule of PCV7 into this population has resulted in a marked and sustained reduction of IPD in children.

From the *Division of Pediatric Infectious Diseases, Stanford University School of Medicine, Stanford, CA; †Kaiser Permanente, Denver, CO; ‡Global Medical Affairs, Wyeth Pharmaceuticals, Collegeville, PA; §Kaiser Permanente Vaccine Study Center, Oakland, CA; and ∥University of Pennsylvania School of Medicine, Philadelphia, PA.

Accepted for publication May 23, 2007.

Address for correspondence: Nicola P. Klein, MD, PhD, Kaiser Permanente Vaccine Study Center, 1 Kaiser Plaza, 16th floor, Oakland, CA 94612. E-mail:

© 2007 Lippincott Williams & Wilkins, Inc.