Impact of parental vaccine concerns on early childhood immunization outcomes

Background: Several vaccine preventable disease outbreaks have been linked to children whose parents refused or delayed school required immunizations. A survey of Oregon parents claiming such exemptions found a high prevalence of vaccine safety and utility concerns. This study identifies concerns that may cause parents to forego timely immunizations for their child, and quantifies the impact on under-immunization. Methods: Oregon mothers were asked about specific immunization concerns two years after responding to the 2004 Pregnancy Risk Assessment Monitoring System survey. Respondents were matched to their child's vaccine record in Oregon's immunization information system (n=865; response rate=39.3%). Children missing >1 recommended immunization by age two were considered under-immunized. Multiple logistic regression modeled associations of parental concerns with under-immunization. Adjusted prevalence ratios (PRs) and population attributable risk measures were calculated. Results: Thirty percent of children were under-immunized. Under-immunized children's mothers were more likely to believe vaccines weaken the immune system (PR: 2.1; 95%CI: 1.4-2.6), vaccines are given too early (PR: 2.0; 95%CI: 1.5-2.5), and diseases wouldn't affect their child (PR: 1.9; 95%CI: 1.3-2.5) compared to fully immunized children. Under-immunized children's mothers were more likely to have multiple concerns (PR: 1.7; 95%CI: 1.3-2.2). Vaccine concerns contributed to 15.6% of under-immunization risk. Conclusions: Parental vaccine concerns may contribute to under-immunization at age two. Efforts to reduce concerns should focus on understanding and dispelling common vaccine myths. Since mothers of fully immunized children also had vaccine concerns, understanding what reasons lead parents with concerns to either vaccinate or not vaccinate is needed.