Vaccine Refusal Increases Risk for Pertussis in Unvaccinated Children

Parents often ask whether refusing immunizations really increases the risk for vaccine-preventable diseases in their children. To find out, investigators conducted a case-control study in 156 children (age range, 2 months to 18 years) with culture-proven pertussis and 595 randomly selected matched controls without pertussis who were enrolled in the Colorado Kaiser Permanente health plan between 1996 and 2007. Documentation of vaccine dates and refusal were obtained from chart review. Overall, 12.0% of cases were vaccine refusers, compared with 0.5% of controls.