Vaccination Rates Lower for Children with Autism and their Siblings

Children with autism spectrum disorder (ASD) and their siblings have lower vaccination rates than the general public, which leaves them at greater risk for vaccine-preventable diseases, according to a new study.

"There were large disparities in vaccination rates between children with and without autism spectrum disorders, as well as between their siblings, across all age groups and after adjusting for important confounding factors," Nicola Klein, MD, PhD, a senior author in the study said in a release announcing the results. Klein is the director of the Kaiser Permanente Vaccine Study Center.

The retrospective cohort study examined data from more than 3,700 children who had been diagnosed with ASD by age 5 and almost 500,000 children without such a diagnosis. Researchers, led by Ousseny Zerbo, PhD, of the Kaiser Permanente Vaccine Study Center, reported that 94% of those children age 7 or older without ASD had received all the vaccinations that are recommended between 4 and 6 years of age; however, just 82% of those with an ASD were fully vaccinated.

This reduction in immunization rates is also seen in younger siblings of children with ASD. According to the study, the adjusted rate ratios of younger siblings of children with ASD varied from 0.86 for siblings under 1 year of age to 0.96 for those 11 to 12 years old, when compared with siblings of children without ASD.

"Being unvaccinated puts a child at increased risk for death and disability from vaccine-preventable diseases," Frank DeStefano, MD, MPH, told Drug Topics. He is a coauthor of the study and director of the CDC's Immunization Safety Office. "Even diseases, such as measles, that are at very low levels in the U.S. are just a plane ride away, as was demonstrated by the Disneyland measles outbreak of a few years ago."

According to DeStefano, although many scientific studies have found no association between vaccination and autism rates, surveys of parents continue to show that some parents are still concerned about a link between the two.

He believes one driver of this continued skepticism could be the success of immunization programs in the United States.

"Many parents today probably have never seen someone with measles or polio or other vaccine-preventable diseases, whereas they are likely to know someone with autism," he said. "Therefore, autism would appear to be a bigger concern than the threat of a vaccine-preventable disease."

Pharmacists and other healthcare professionals can work to combat this lingering skepticism by talking with patients about the importance of timely vaccinations.

"The most important influence on a parent's vaccination decisions is the recommendation of a trusted healthcare provider," DeStefano said. "Even parents who are hesitant about vaccination are likely to have their children vaccinated if recommended by the child's pediatrician or primary care physician."

The encouraging news that emerged from the study, he said, is that although children with ASD had lower rates of vaccination than those who didn't, overall, the majority of children with ASD were fully vaccinated.