Frequencies of Vaccine Uptake in Children with Autism Spectrum Disorder and Type of Onset Described By Parents

Background: A highly controversial theory for ASD is that regressive-onset ASD is triggered by vaccines. If vaccines are associated specifically with developmental regression in ASD, then it follows that vaccination rates should be significantly higher among children with ASD plus regression. Two studies conducted outside the U.S. found no association between the MMR vaccine and regression in ASD; however, these works only focused on one type of vaccine and did not examine ASD onset more broadly. The current study extended this line of work to examine potential associations between different types of ASD onset—not just regression—and a variety of vaccines that children routinely receive between birth and age 3 years. Focus was on both proportion of vaccine uptake and proportion of non-delay (i.e., accepting the vaccine at the time it was offered) for each vaccine.

Objectives: To examine whether vaccine-uptake and non-delay rates were equivalent among in a large sample of children with confirmed ASD diagnoses who had different types of autism onset (early onset, plateau, delays + regression, regression).  

Methods: Data were analyzed for children with ASD (N = 2755; 86.4% male; M age = 9 years, SD = 3.6 years, range = 4—17.9 years; 78.5% White, 88.8% non-Hispanic) who participated in the Simons Simplex Collection (SSC). Onset categories for ASD were created using various combinations of responses to select items from the Autism Diagnostic Interview—Revised (ADI-R) to group children into one of the following four ASD-onset types: early onset, plateau, delay + regression, or regression. Vaccination history was obtained as part of an extensive Medical History Interview (MHI) conducted with children's parents; families were permitted to send in shot records for these data. Focus was on the following vaccines queried during the MHI: DPT/DTaP, HepB, HiB, poliovirus oral/injected, MMR, chicken pox/varicella. Equivalence for uptake and non-delay for each type of vaccine was assessed by deriving the risk difference of the percentage of vaccine uptake between all pairwise comparisons for ASD-onset groups using a two-sided 90% confidence interval.

Results: Proportions of children in each ASD-onset group were 33.5%for early onset, 36.5% for plateau, 10% for delay + regression, and 20% for regression. Vaccine-uptake rates ranged from 79% to 99%; non-delay rates ranged from 92% to 98%. All pairwise group comparisons for vaccine uptake and non-delayed administration were statistically significantly equivalent (adj p < .05), with the exception of varicella, for which the early onset/delay + regression comparison and the delay + regression/regression comparison were not equivalent for uptake (adj p = .07). The early-onset (85%) and regression (83%) groups each had higher rates of uptake than the delay + regression group (79%).

Conclusions: Equivalence was demonstrated between all ASD-onset types for each vaccine except varicella; however, differences between groups were not considered clinically meaningful (4—6% difference). Moreover, uptake proportions for early-onset and regression were equivalent. This, in conjunction with equivalent uptake across onset groups for all other vaccines, does not support the theory of an association between vaccines and regressive-onset ASD.