title: Effectiveness of seven-valent pneumococcal conjugate vaccine against invasive pneumococcal disease: a matched case-control study.
abstract: BACKGROUND
  When seven-valent pneumococcal conjugate vaccine was introduced in the USA, many children were vaccinated on schedules that differed from those tested in clinical trials. Our aim was to assess the effectiveness of the vaccine against various pneumococcal serotypes, and to measure the effectiveness of the recommended dose schedule and of catch-up and incomplete schedules.
  
  
  METHODS
  Invasive disease, defined as isolation of pneumococcus from a sterile site, was identified in children aged 3-59 months through the US Centers for Disease Control and Prevention's Active Bacterial Core surveillance. We tested isolates for serotype and antimicrobial susceptibility. Three controls, matched for age and zip code were selected for each case. We calculated the matched odds ratio for vaccination using conditional logistic regression, controlling for underlying conditions. Vaccine effectiveness was calculated as one minus the adjusted matched odds ratio times 100%.
  
  
  RESULTS
  We enrolled 782 cases and 2512 controls. Effectiveness of one or more doses against vaccine serotypes was 96% (95% CI 93-98) in healthy children and 81% (57-92) in those with coexisting disorders. It was 76% (63-85) against infections that were not susceptible to penicillin. Vaccination prevented disease caused by all seven vaccine serotypes, and by vaccine-related serotype 6A. Several schedules were more protective than no vaccination; three infant doses with a booster were more protective against vaccine-type disease than were three infant doses alone (p=0.0323).
  
  
  CONCLUSIONS
  The seven-valent pneumococcal conjugate vaccine prevents invasive disease in both healthy and chronically ill children. The vaccine is effective when used with various non-standard schedules.
authors.affiliation: Division of Bacterial and Mycotic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, GA, USA. cwhitney@cdc.gov
authors.forename: Cynthia G
authors.initials: CG
authors.lastname: Whitney
authors.forename: Tamar
authors.initials: T
authors.lastname: Pilishvili
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: Allen S
authors.initials: AS
authors.lastname: Craig
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
authors.forename: Ann-Christine
authors.initials: AC
authors.lastname: Nyquist
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Gershman
authors.forename: Marietta
authors.initials: M
authors.lastname: Vazquez
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Bennett
authors.forename: Arthur
authors.initials: A
authors.lastname: Reingold
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: Mary P
authors.initials: MP
authors.lastname: Glode
authors.forename: Elizabeth R
authors.initials: ER
authors.lastname: Zell
authors.forename: James H
authors.initials: JH
authors.lastname: Jorgensen
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
authors.forename: Anne
authors.initials: A
authors.lastname: Schuchat
mesh_terms: D016022:Case-Control Studies; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D007223:Infant; D016015:Logistic Models; D008297:Male; D022242:Pneumococcal Vaccines / Q000494:pharmacology*; D011014:Pneumonia / Q000517:prevention & control*; D015397:Program Evaluation; D012703:Serotyping; D013296:Streptococcus pneumoniae / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification; D014481:United States
chemical_list: D022242:Pneumococcal Vaccines