Objective: To examine the attitudes, beliefs, and behaviors of parents whose children were underimmunized with respect to > or =2 vaccines that have recently received negative attention, compared with parents whose children were fully immunized with respect to the recommended vaccines.
Design: Case-control study.
Setting: A sample of households that participated in the National Immunization Survey were recontacted in 2001.
Main outcome measure: Vaccination status was assessed. Case subjects were underimmunized with respect to > or =2 of 3 vaccines (diphtheria-tetanus-pertussis or diphtheria-tetanus-acellular pertussis, hepatitis B, or measles-containing vaccines), and control subjects were fully immunized.
Results: The response rate was 52.1% (2315 of 4440 subjects). Compared with control households, case households were more likely to make 0 dollar to 30,000 dollars (adjusted odds ratio [OR]: 2.7; 95% confidence interval [CI]: 1.5-4.6) than at least 75,000 dollars, to have > or =2 providers (OR: 2.0; 95% CI: 1.3-3.1) than 1, and to have > or =4 children (OR: 3.1; 95% CI: 1.5-6.3) than 1 child. With control for demographic and medical care factors, case subjects were more likely than control subjects to not want a new infant to receive all shots (OR: 3.8; 95% CI: 1.5-9.8), to score vaccines as unsafe or somewhat safe (OR: 2.0; 95% CI: 1.2-3.4), and to ask the doctor or nurse not to give the child a vaccine for reasons other than illness (OR: 2.7; 95% CI: 1.2-6.1). Among case subjects, 14.8% of underimmunization was attributable to parental attitudes, beliefs, and behaviors.
Conclusions: Attitudes, beliefs, and behaviors indicative of vaccine safety concerns contribute substantially to underimmunization in the United States. Although concerns were significantly more common among parents of underimmunized children, many parents of fully immunized children demonstrated similar attitudes, beliefs, and behaviors, suggesting a risk to the currently high vaccination levels. Efforts to maintain and improve immunization coverage need to target those with attitudes/beliefs/behaviors indicative of vaccine safety concerns, as well as those with socioeconomic and health care access problems.