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Children with autism, their siblings less likely to be completely vaccinated
Children who have been diagnosed with ASD and their younger siblings are significantly less likely to be completely vaccinated, with the greatest rates of undervaccination observed in siblings between 1 to 11 months and 1 to 2 years, according to findings published in JAMA Pediatrics.
“The etiology of autism spectrum disorder is unknown for the vast majority of cases; however, study findings suggest that both genetic and environmental factors have a role,” Ousseny Zerbo, PhD, from the Kaiser Permanente Vaccine Study Center, and colleagues wrote. “Despite numerous scientific studies reporting no association between childhood vaccination and ASD, there remain concerns about such a connection from some of the public.”
“In recent years, rates of undervaccination and vaccine refusal have been on the rise in the United States and have been associated with vaccine-preventable disease outbreaks,” the researchers continued. “Rates of undervaccination among the subpopulation of children with ASD have not been fully investigated.”
To examine whether children with an ASD diagnosis continue to receive immunizations according to the Advisory Committee on Immunization Practices (ACIP) schedule, and to relate their younger siblings’ vaccination status to younger siblings of children without ASD, the researchers conducted a retrospective matched cohort study. All information was collected from six U.S.-based integrated health care delivery systems, which were accessed through the Vaccine Safety Datalink.
All children assessed were born between Jan. 1, 1997, and Sept. 30, 2014. The last follow-up session occurred on Sept. 30, 2015. The researchers were made aware of the vaccines recommended for children between ages 1 month and 12 years to determine the proportion of children who had received all recommended immunizations.
When compared to children without ASD (n = 592,907), those diagnosed with the disorder (n = 3,729) were significantly less likely to complete all recommended immunizations for children between 4 and 6 years of age (adjusted RR, 0.87; 95% CI, 0.85-0.88). The researchers observed lower vaccination rates in younger siblings of children with ASD when compared with younger siblings of children without ASD.
For younger siblings of children with ASD, the researchers observed a range of adjusted rate ratios, from 0.86 in children younger than 1 year to 0.96 for siblings between the ages of 11 and 12. Zerbo and colleagues also observed that parents were likely to deny vaccination for one or more recommended immunizations for younger siblings of children with ASD. Additionally, these parents also were more likely to deny vaccination within younger siblings’ first years of life.
“The highest rates of undervaccination in this study were among siblings of children with ASD who were in groups aged 1 to 11 months and 1 to 2 years,” Zerbo and colleagues wrote. “This suggests that some parents consider the potential risks of ASD associated with vaccinations to be greatest at these younger ages at which more vaccines are recommended. However, as these children grow older, these parents may be more willing to vaccinate.” – by Katherine Bortz
Disclosures: Zerbo reports no relevant financial disclosures. Please see the study for a full list of other authors’ relevant financial disclosures.
