ORs and Percent Attributable Risks for Risk of Pertussis in Primary and Secondary Case-Control Analyses

OR (95% CI)% AR Refusers (95% CI)% AR Population (95% CI)
Case-control study
    Refused vaccination (all ages)22.8 (6.7–77.5)a99.5 (98.1–99.9)11.0 (5.9–16.0)
Secondary case-control studyb
    Refused vaccination (2–20 mo)19.3 (3.5–104.5)a99.3 (95.4–99.9)12.2 (0.0–23.4)
  • The reference group for all ORs is children who received the full schedule of pertussis vaccinations. AR indicates attributable risk.

  • a P < .001.

  • b Secondary analysis with subjects who were continuously enrolled in the health plan between 2 and 20 months of age.