Beliefs about Causes of Autism and Current Vaccine Hesitancy: Comparisons Across FOUR Parent Groups

Background:  Unfounded fear about a connection between childhood vaccines and autism spectrum disorder (ASD) has been proposed as a leading reason behind a growing number of vaccine delays and refusals. An estimated 20-30% of parents are vaccine hesitant—meaning they have considerable vaccine concerns and may delay or refuse one or more vaccines. Identifying groups of parents more likely to become vaccine hesitant and factors that predict vaccine hesitancy are key to the design and success of tailored, preemptive vaccine-safety educational strategies.

Objectives: To (a) compare parents’ beliefs about causes of their children’s developmental delays/chronic illness and rates of vaccine hesitancy among parents of children in four groups: those with ASD (ASD), those for whom ASD was ruled out(ASD-RO), those with a diagnosed rheumatoid disorder (RD), and those in the general pediatric population (GP); and (b) identify factors that may differentially associate with vaccine hesitancy across groups.

Methods: Data were collected from 165 parents of children seen at the Autism Center at Texas Children's Hospital and enrolled in a research registry (76% ASD; 24% ASD-RO). Families who had agreed to be contacted about new studies were mailed packets that contained a cover letter, a Parent Attitudes About Childhood Vaccines questionnaire (PACV; measure of vaccine hesitancy), a Revised Illness Perception Questionnaire(IPQ-R; measure of attributions about children’s diagnoses and etiological beliefs), and a demographic form. Clinical diagnoses (ASD or ASD-RO) were extracted from the electronic medical record by one co-author and validated by a second. A logistic regression model was used to estimate the odds ratio for vaccine hesitancy with 95% confidence intervals. Variables significant at the 0.20 level in the univariable analysis were included in the multiple logistic regression model, adjusting for diagnostic group (ASD or ASD-RO). Data collection from the RD and GP groups is currently ongoing, with comparable analyses planned.

Results: Overall, 39/165 (23.6%) of parents agreed that toxins in vaccines caused their child’s developmental difficulties, while 40/165 (24.2%) were vaccine hesitant (PACV score ≥ 50). Compared to parents in the ASD-RO group, parents in the ASD group were more likely to believe that vaccines contributed to their child’s developmental difficulties (27.0% vs. 12.8%) and significantly more likely to be vaccine hesitant (28.6% vs. 10.3%, Fisher’s p< 0.02). The odds of being vaccine hesitant were 2.8 times higher among parents endorsing environmental pollution as a cause for their child’s difficulties (95%CI: 1.1—7.6) and 12.8 times higher among parents endorsing toxins in vaccines as a cause (95%CI: 4.5—36.2), which were the only factors maintaining statistical significance in the full model (Figure 1). Additional results with the RD and GP groups are forthcoming.

Conclusions: This comparison between the ASD and ASD-RO groups is interesting in that children in both groups had been referred for possible ASD; final diagnosis—ASD or not ASD—was a distinguishing factor associated with current parental vaccine hesitancy. Comparisons among the RD and GP groups will further elucidate whether a child’s ASD diagnosis and/or other factors confer particular risk for becoming vaccine hesitant.