title: Use of surveillance data to estimate the effectiveness of the 7-valent conjugate pneumococcal vaccine in children less than 5 years of age over a 9 year period.
abstract: BACKGROUND
  Case-control studies evaluating post-licensure effectiveness of conjugate vaccines can be laborious and costly. We applied an indirect cohort method to evaluate the effectiveness of seven-valent pneumococcal conjugate vaccine (PCV7) against invasive pneumococcal disease (IPD) and compared the results to the effectiveness measured using a standard case-control study conducted during the same time period.
  
  
  METHODS
  IPD cases among children 2-59 months old were identified through the Active Bacterial Core surveillance system during 2001-2009. We used logistic regression to calculate the odds ratio of vaccination (versus no vaccination) among cases (PCV7-type IPD cases) and non-cases (non-PCV7-type IPD cases), controlling for the presence of underlying conditions. Vaccine effectiveness (VE) was calculated as one minus the adjusted odds ratio.
  
  
  RESULTS
  Among 4225 IPD cases reported during 2001-2009, 2680 (63%) had serotype information and vaccine history. Effectiveness of ≥ 1 dose of PCV7 against PCV7-types was 88% (95% confidence interval (CI) 78-94%) among children with comorbid conditions and 97% (95% CI 92-98%) among healthy children. Among healthy children, VE was higher in 2001-2003 (97%, 95% CI 95-98%) compared to 2004-2009 (81%, 95% CI 64-90%). The annual estimates of VE in 2004-2009 showed great variability and wide confidence intervals due to the small number of PCV7-type cases.
  
  
  CONCLUSIONS
  An indirect cohort design using IPD surveillance data confirms the findings of the case-control study and, therefore, appears suitable for estimating PCV7 effectiveness. This method would be most useful shortly after vaccine introduction, and less useful in a setting of very high vaccine coverage and fewer vaccine-type cases.
authors.affiliation: Institut National de Santé Publique du Québec and Laval University, Québec, Canada.
authors.forename: Gaston
authors.initials: G
authors.lastname: De Serres
authors.forename: Tamara
authors.initials: T
authors.lastname: Pilishvili
authors.forename: Ruth
authors.initials: R
authors.lastname: Link-Gelles
authors.forename: Arthur
authors.initials: A
authors.lastname: Reingold
authors.forename: Kenneth
authors.initials: K
authors.lastname: Gershman
authors.forename: Susan
authors.initials: S
authors.lastname: Petit
authors.forename: Monica M
authors.initials: MM
authors.lastname: Farley
authors.forename: Lee H
authors.initials: LH
authors.lastname: Harrison
authors.forename: Ruth
authors.initials: R
authors.lastname: Lynfield
authors.forename: Nancy M
authors.initials: NM
authors.lastname: Bennett
authors.forename: Joan
authors.initials: J
authors.lastname: Baumbach
authors.forename: Ann
authors.initials: A
authors.lastname: Thomas
authors.forename: William
authors.initials: W
authors.lastname: Schaffner
authors.forename: Bernard
authors.initials: B
authors.lastname: Beall
authors.forename: Cynthia
authors.initials: C
authors.lastname: Whitney
authors.forename: Matthew
authors.initials: M
authors.lastname: Moore
mesh_terms: D016470:Bacteremia / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D006801:Humans; D007223:Infant; D008297:Male; D008586:Meningitis, Pneumococcal / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control; D011008:Pneumococcal Infections / Q000453:epidemiology* / Q000276:immunology / Q000517:prevention & control*; D022242:Pneumococcal Vaccines / Q000008:administration & dosage* / Q000276:immunology*; D016896:Treatment Outcome
chemical_list: D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D022242:Pneumococcal Vaccines