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Original Investigation
May 2018

Vaccination Patterns in Children After Autism Spectrum Disorder Diagnosis and in Their Younger Siblings

Author Affiliations
  • 1Kaiser Permanente Vaccine Study Center, Oakland, California
  • 2Institute for Health Research, Kaiser Permanente Colorado, Denver
  • 3Center for Health Research, Kaiser Permanente Northwest, Portland, Oregon
  • 4Kaiser Permanente Washington, Seattle
  • 5Center for Clinical Epidemiology & Population Health, Marshfield Clinic Research Institute, Marshfield, Wisconsin
  • 6Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena
  • 7Immunization Safety Office, Centers for Disease Control and Prevention, Atlanta, Georgia
JAMA Pediatr. 2018;172(5):469-475. doi:10.1001/jamapediatrics.2018.0082
Key Points

Question  After receiving an autism spectrum disorder diagnosis, do children obtain all of their remaining scheduled vaccines, and are the younger siblings of these children vaccinated according to vaccine recommendations?

Findings  In a matched cohort study of 3729 children with autism spectrum disorder and 592 907 children without autism spectrum disorder, we found that children with autism spectrum disorder were less likely to be fully vaccinated for vaccines recommended between ages 4 and 6 years. The younger siblings were also less likely to be fully vaccinated for vaccines recommended at any age.

Meaning  Children with autism spectrum disorder and their younger siblings are at increased risk of vaccine-preventable diseases.

Abstract

Importance  In recent years, rates of vaccination have been declining. Whether this phenomenon disproportionately affects children with autism spectrum disorder (ASD) or their younger siblings is unknown.

Objectives  To investigate if children after receiving an ASD diagnosis obtain their remaining scheduled vaccines according to the Advisory Committee on Immunization Practices (ACIP) recommendations and to compare the vaccination patterns of younger siblings of children with ASD with the vaccination patterns of younger siblings of children without ASD.

Design, Setting, and Participants  This investigation was a retrospective matched cohort study. The setting was 6 integrated health care delivery systems across the United States within the Vaccine Safety Datalink. Participants were children born between January 1, 1995, and September 30, 2010, and their younger siblings born between January 1, 1997, and September 30, 2014. The end of follow-up was September 30, 2015.

Exposures  Recommended childhood vaccines between ages 1 month and 12 years.

Main Outcome and Measure  The proportion of children who received all of their vaccine doses according to ACIP recommendations.

Results  The study included 3729 children with ASD (676 [18.1%] female), 592 907 children without ASD, and their respective younger siblings. Among children without ASD, 250 193 (42.2%) were female. For vaccines recommended between ages 4 and 6 years, children with ASD were significantly less likely to be fully vaccinated compared with children without ASD (adjusted rate ratio, 0.87; 95% CI, 0.85-0.88). Within each age category, vaccination rates were significantly lower among younger siblings of children with ASD compared with younger siblings of children without ASD. The adjusted rate ratios varied from 0.86 for siblings younger than 1 year to 0.96 for those 11 to 12 years old. Parents who had a child with ASD were more likely to refuse at least 1 recommended vaccine for that child’s younger sibling and to limit the number of vaccines administered during the younger sibling’s first year of life.

Conclusions and Relevance  Children with ASD and their younger siblings were undervaccinated compared with the general population. The results of this study suggest that children with ASD and their younger siblings are at increased risk of vaccine-preventable diseases.

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