Vaccine Hesitancy and Attributions for Autism in the SPARK Cohort

Background: Although some data indicate that children diagnosed with autism spectrum disorder (ASD) are well-vaccinated until 2 years of age, new evidence suggests that vaccine receipt may decline later in childhood. Moreover, younger siblings of children with ASD often have lower rates of vaccine receipt compared to both their older siblings and younger siblings of children without ASD. This suggests that parents of children with ASD may be at risk for becoming vaccine hesitant, resulting in concerns about vaccine safety and possible vaccine delay and/or refusal.

Objectives: To (a) estimate the prevalence of vaccine-hesitant parents (VHP) within the SPARK (Simons Foundation Powering Autism Research for Knowledge) cohort—a national sample of families with at least one member experiencing ASD—using the Parent Attitudes About Childhood Vaccines questionnaire (PACV; scores ≥ 50 indicate vaccine hesitancy); (b) describe attributions for ASD in this sample using the Revised Illness Perception Questionnaire for parents of children with ASD (IPQ-R-ASD); and (c) identify factors associated with vaccine hesitancy.

Methods: Invitations to participate in an online survey were emailed to 1,000 SPARK parents of minor children with simplex ASD; 225 parents (23%) responded. The majority were white (75%, n=168) and mothers (92%, n=207). Descriptive statistics were used to determine the prevalence of VHP, distribution of PACV scores, and average scores for IPQ-R-ASD subscales (Timeline-Acute/Chronic, Timeline-Cyclical, Consequences, Personal Control, Treatment Control, Illness Coherence, Emotional Representations). Multivariable logistic regression was used to estimate the odds ratio for vaccine hesitancy.

Results: Overall, 29% (65/225; 95% CI: 23%, 35%) of parents were vaccine hesitant. VHP had lower incomes (p=0.007), were less likely to be white (p=0.002), and were more likely to endorse accident/injury (13% vs. 4%; p=0.027), deterioration of the child’s immunity (29% vs. 4.5%; p<0.001), diet (40% vs. 16%; p<0.001), environmental pollution (50% vs. 30%; p=0.007), general stress (47% vs. 26%; p=0.006), negative views (13% vs. 5%; p=0.038), own decisions (21% vs. 6%; p=0.002), own emotional state (27% vs. 13%; p=0.016), and toxins in vaccines (65% vs. 3%; p<0.001) as causes for their child’s ASD. Compared to non-hesitant parents, VHP scored higher on the Personal Control (M=18.9 vs. 18.0, p=.011), Treatment Control (M=13.5 vs. 12.3, p<.003), Illness Coherence (M=15.5 vs. 14.3, p=.019), and Emotional Representations (M=18.2 vs. 16.0, p<.002) subscales of the IPQ-R. The final multiple logistic regression included two causes for ASD: general stress and vaccines. The odds of being vaccine hesitant were 3.3 (95%CI: 1.4, 7.6) times higher among parents endorsing general stress as a cause for their child’s ASD and 61.5 (95%CI: 21, 180) times higher among parents endorsing toxins in vaccines as a cause.

Conclusions: Endorsement of general stress and vaccines as causes of ASD were associated with current vaccine hesitancy among SPARK parents. Based on IPQ-R subscales, VHP felt they had more control over their child’s ASD, a clearer understanding of ASD, yet reported more negative feelings about their child’s ASD compared to non-hesitant parents. This information could inform the development of preemptive vaccine-safety information targeted to parents of children with ASD.