OBJECTIVES To examine patterns and trends of undervaccination in children aged 2 to 24 months and to compare health care utilization rates between undervaccinated and age-appropriately vaccinated children. DESIGN Retrospective matched cohort study. SETTING Eight managed care organizations of the Vaccine Safety Datalink. PARTICIPANTS Children born between 2004 and 2008. MAIN EXPOSURE Immunization records were used to calculate the average number of days undervaccinated. Two matched cohorts were created: 1 with children who were undervaccinated for any reason and 1 with children who were undervaccinated because of parental choice. For both cohorts, undervaccinated children were matched to age-appropriately vaccinated children by birth date, managed care organization, and sex. MAIN OUTCOME MEASURES Rates of undervaccination, specific patterns of undervaccination, and health care utilization rates. RESULTS Of 323 247 children born between 2004 and 2008, 48.7% were undervaccinated for at least 1 day before age 24 months. The prevalence of undervaccination and specific patterns of undervaccination increased over time (P < .001). In a matched cohort analysis, undervaccinated children had lower outpatient visit rates compared with children who were age-appropriately vaccinated (incidence rate ratio [IRR], 0.89; 95% CI, 0.89- 0.90). In contrast, undervaccinated children had increased inpatient admission rates compared with age-appropriately vaccinated children (IRR, 1.21; 95% CI, 1.18-1.23). In a second matched cohort analysis, children who were undervaccinated because of parental choice had lower rates of outpatient visits (IRR, 0.94; 95% CI, 0.93-0.95) and emergency department encounters (IRR, 0.91; 95% CI, 0.88-0.94) than age-appropriately vaccinated children. CONCLUSIONS Undervaccination appears to be an increasing trend. Undervaccinated children appear to have different health care utilization patterns compared with age-appropriately vaccinated children.
"Parents in the United States, Australia, and the United Kingdom (among other countries) are increasingly refusing routine childhood vaccines (Omer et al. 2009; Omer et al. 2012; Nicholson and Ramet 2013; Konner 2011; Glanz et al. 2013). Many of these 'vaccine refusers' invoke ideas about sanctity. "
[Show abstract][Hide abstract] ABSTRACT: Vaccine refusers often seem motivated by disgust, and they invoke ideas of purity, contamination and sanctity. Unfortunately, the emotion of disgust and its companion ideas are not directly responsive to the probabilistic and statistical evidence of research science. It follows that increased efforts to promulgate the results of vaccine science are not likely to contribute to increased rates of vaccination among persons who refuse vaccines because of (what has been called) the ‘ethics of sanctity’. Furthermore, the fact that disgust-based vaccine refusal is not monolithic – vaccine refusers manifest disgust at different objects and invoke different ideas about purity and contamination – further complicates public health efforts to increase vaccination rates.
"An obvious way around this problem is to include unvaccinated children in the study population. However, unvaccinated persons may differ in important ways from vaccinated persons in terms of factors including socioeconomic status, parental education, likelihood that a parent will bring a child in for evaluation of events or illnesses, and other sociodemographic factors  . Controlling for confounding in studies including unvaccinated persons may be more difficult then when samples are restricted to vaccinated persons. "
[Show abstract][Hide abstract] ABSTRACT: As vaccine hesitancy has increased in the United States, various authors have begun proposing alternatives to the Advisory Committee on Immunization Practices' recommended childhood immunization schedule. Because parents may believe the safety claims made by such authors, evaluations of the safety of alternative vaccination schedules are needed. However, comparing the safety of different vaccination schedules has numerous methodologic challenges. These challenges include defining vaccination history, defining safety, appropriately modeling interactions between vaccines, and appropriately handling age effects. Failure to properly address these challenges can result in biased results.
[Show abstract][Hide abstract] ABSTRACT: A cluster randomized trial was performed to evaluate an educational intervention to improve parental attitudes and vaccine uptake in vaccine-hesitant parents.
Two primary care sites were randomized to provide families with either usual care or an intervention (video and written information) for vaccine-hesitant parents. Eligible parents included those presenting for their child's 2-week well-child visit with performance on the Parent Attitudes about Childhood Vaccines (PACV) survey suggesting vaccine hesitancy (score ≥25). Enrollees completed PACV surveys at the 2-month well-child visit and vaccination status at 12 weeks of age was assessed. The primary outcome was the difference in PACV scores obtained at enrollment and 2 months between the 2 groups. The proportion of on-time vaccination was also compared at 12 weeks.
A total of 454 parents were approached, and 369 (81.3%) participated; 132 had PACV scores of ≥25 and were enrolled, 67 in the control group (mean PACV score 37) and 55 in the intervention group (mean PACV score 40). Two-month PACV surveys were completed by 108 (∼90%) of enrollees. Parents in the intervention group had a significant decrease in PACV score at 2 months compared to control (median difference 6.7, P = .049); this remained significant after adjustment for baseline PACV score, race/ethnicity, and income (P = .044). There was no difference in the on-time receipt of vaccines between groups at 12 weeks.
A brief educational intervention for vaccine-hesitant parents was associated with a modest but significant increase in measured parental attitudes toward vaccines.
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