title: Methodological issues in design and analysis of a matched case-control study of a vaccine's effectiveness.
abstract: OBJECTIVE
  Case-control studies of the effectiveness of a vaccine are useful to answer important questions, such as the effectiveness of a vaccine over time, that usually are not addressed by prelicensure clinical trials of the vaccine's efficacy. This report describes methodological issues related to design and analysis that were used to determine the effects of time since vaccination and age at the time of vaccination.
  
  
  METHODS
  A matched case-control study of the effectiveness of varicella vaccine was conducted.
  
  
  RESULTS
  Sampling procedures and conditional logistic regression models including interaction terms are described.
  
  
  CONCLUSIONS
  Use of these methods will allow investigators to assess the effects of a wide range of variables, such as time since vaccination and age at the time of vaccination, on the effectiveness of a vaccine.
authors.affiliation: Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT 06520-8064, USA.
authors.forename: Linda M
authors.initials: LM
authors.lastname: Niccolai
authors.forename: Lorraine G
authors.initials: LG
authors.lastname: Ogden
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Muehlenbein
authors.forename: James D
authors.initials: JD
authors.lastname: Dziura
authors.forename: Marietta
authors.initials: M
authors.lastname: Vázquez
authors.forename: Eugene D
authors.initials: ED
authors.lastname: Shapiro
mesh_terms: D000367:Age Factors; D016022:Case-Control Studies; D019433:Chickenpox Vaccine / Q000627:therapeutic use*; D015340:Epidemiologic Research Design; D006801:Humans; D016015:Logistic Models; D016017:Odds Ratio; D018579:Patient Selection; D018570:Risk Assessment; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D019433:Chickenpox Vaccine