An Examination of Vaccination Rates and Related Factors in Children and Adolescents with Autism Spectrum Disorder

Background: Youth with ASD may be under-vaccinated for many reasons, including: 1) persisting parental beliefs in a connection between vaccines and ASD, 2) difficulty with medical procedures, including needles, experienced by many youth with ASD, and 3) factors contributing to vaccine hesitancy in the general population. Understanding of vaccination uptake in youth with ASD is limited, and studies to date have primarily assessed vaccination status through parent report.

Objectives: We sought to determine whether vaccination rates in school-aged youth with ASD differ from those of their peers without ASD.

Methods: We conducted a retrospective cohort study by linking perinatal, administrative health, and vaccination databases. We included youth born between 1992 and 2005 in Nova Scotia (NS), Canada. ASD cases were identified using our previously developed, validated, and published algorithm. In our main analysis, youth with ASD were compared to their peers without ASD in the general population regarding uptake of scheduled school-based vaccinations. The primary outcome variable was receipt/non-receipt/partial receipt (i.e., not all doses) of any scheduled school-based vaccine and was determined using Public Health and physician billing databases. Chi square tests were used to test the association between vaccine receipt among youth with ASD compared to peers without ASD.

Results: Our overall cohort size was 41,287 (of which 746 had ASD) for Hepatitis B and Tetanus, Diphtheria, and Pertussis (TDAP) vaccines and 24,527 (of which 256 had ASD) for Human Papillomavirus (HPV) vaccine, due to a later introduction of the HPV vaccine. For receipt of any vaccine, youth with ASD were less likely to be vaccinated (71%) than their peers without ASD (78%), p < 0.0001. For Hepatitis B, 58% of youth with ASD were fully vaccinated and 13% were partially vaccinated vs. 67% and 11%, respectively among youth without ASD (p<0.0001). Similarly, for TDAP, 68% of youth without ASD were vaccinated vs. 60% of youth with ASD (p<0.0001). Vaccination rates were even more divergent for HPV, with 72% of youth without ASD being vaccinated vs. 57% of youth with ASD. (p<0.0001).

Conclusions: This project is important because it suggests that school-aged youth with ASD are at high risk of under-vaccination. Vaccines are a critical component of our disease-prevention strategy, and youth with ASD represent at least 1% of the population. Under-vaccination in this group would contribute to an increased risk of infectious disease for youth with ASD, their families, and the community. Strategies for delivering school-based vaccines to accommodate the unique needs of youth with ASD should to be considered.