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