Background and objectives: With vaccine-preventable diseases at record lows, few studies investigate rising parent-claimed exemptions to school immunization requirements. After finding exemption clusters in Oregon, we hypothesized that exemption risk factors may vary among communities. We surveyed parents to identify risk factors for exemptions and evaluated risk factor differences among communities with differing exemption rates.
Design: Retrospective cohort study, multi-staged, population-proportionate sampling.
Setting and participants: Parents of 2004-05 Oregon elementary school children (N=2900).
Main outcome measure: Parent-reported exemption status.
Results: The response rate was 55%. Compared to vaccinators, exemptors were significantly more likely to have: strong vaccine concerns (weighted adjusted odds ratio (aOR)=15.3, 95% CI 6.4-36.7); "vaccine-hesitant" concerns (aOR=2.3; 95% CI 1.0-5.0); >1 childbirth(s) at a non-hospital, alternative setting (aOR=3.6; 95% CI 1.6-8.0); distrust of local doctors (aOR=2.7; 95% CI 1.0-7.5); reported chiropractic healthcare for their youngest school-age child (aOR=3.9; 95% CI 1.8-8.5); and reported knowledge of someone with a vaccine-hurt child (aOR=1.8; 95% CI 0.9-3.4). Exemptors were less likely to have "pro-vaccine" beliefs (aOR=0.2; 95% CI 0.0-0.6) and less likely to report relying on print materials (aOR=0.4; 95% CI 0.2-0.8). The strengths of association differed significantly for those with strong vaccine concerns and those reporting knowledge of someone with a vaccine-hurt child, depending on residence in exemption-rate areas, e.g., exemptors in medium-rate areas were more likely to have strong vaccine concerns (aOR=13.5; 95% CI 5.4-34.0) than those in high-rate areas (aOR=9.7; 95% CI 3.7-25.4).
Conclusions: Vaccine beliefs were important risk factors. That differing community-level exemption use modified the effects of several individual-level factors suggests that communities also influence parent decisions. Therefore, understanding community contexts and norms may be important when designing interventions.
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