title: Effectiveness of pertussis vaccines for adolescents and adults: case-control study.
abstract: OBJECTIVE
  To assess the effectiveness of reduced acellular pertussis (Tdap) vaccines in adolescents and adults.
  
  
  METHODS
  Kaiser Permanente Northern California.
  
  
  METHODS
  Case-control study.
  
  
  METHODS
  All polymerase chain reaction (PCR) confirmed cases of pertussis in members aged 11 years and older from January 2006 to December 2011. We compared the Tdap vaccination status of PCR positive cases with two control groups: people testing negative for pertussis by PCR and closely matched people from the general Kaiser Permanente Northern California population.
  
  
  METHODS
  PCR confirmed pertussis. The association of Tdap vaccination with the odds of pertussis infection was estimated by conditional logistic regression, with adjustment for calendar time, pertussis vaccine type received in early childhood, age, sex, race or ethnic group, and medical clinic. We calculated Tdap vaccine effectiveness as 1 minus the adjusted odds ratio.
  
  
  RESULTS
  The study population included 668 PCR positive cases, 10,098 PCR negative controls, and 21,599 Kaiser Permanente Northern California matched controls. Tdap vaccination rates were 24.0% in PCR positive cases and 31.9% in PCR negative controls (P<0.001). The adjusted estimate of effectiveness of Tdap vaccination against pertussis was 53.0% (95% confidence interval 41.9% to 62.0%) in the comparison with PCR controls, and 64.0% (55.5% to 70.9%) in the comparison with Kaiser Permanente Northern California controls.
  
  
  CONCLUSIONS
  Tdap vaccination was moderately effective at preventing PCR confirmed pertussis among adolescents and adults.
authors.affiliation: Kaiser Permanente Vaccine Study Center, 1 Kaiser Plaza, Oakland, CA 94612, USA.
authors.forename: Roger
authors.initials: R
authors.lastname: Baxter
authors.forename: Joan
authors.initials: J
authors.lastname: Bartlett
authors.forename: Ali
authors.initials: A
authors.lastname: Rowhani-Rahbar
authors.forename: Bruce
authors.initials: B
authors.lastname: Fireman
authors.forename: Nicola P
authors.initials: NP
authors.lastname: Klein
mesh_terms: D000293:Adolescent; D000328:Adult; D002140:California / Q000453:epidemiology; D016022:Case-Control Studies; D002648:Child; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D010567:Pertussis Vaccine / Q000627:therapeutic use*; D014917:Whooping Cough / Q000453:epidemiology / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D010567:Pertussis Vaccine