(CNN) Children with autism spectrum disorder are significantly less likely to be fully vaccinated than children unaffected by autism, new research finds. And the same is true of their younger sisters and brothers.
“This study is showing that children with autism and their younger siblings might be at greater risk of vaccine-preventable diseases,” said Ousseny Zerbo, lead author of the study and a postdoctoral fellow with the Kaiser Permanente Northern California Division of Research.
The study was published Monday in the journal JAMA Pediatrics.
‘Large disparities’ in rates
Autism is a neurodevelopmental disorder characterized by challenges with social skills, communication and repetitive behaviors. The cause of autism spectrum disorder is unknown, though research suggests that both genetic and environmental factors play a role.
Scientific studies also report no association between vaccines and autism, although many parents fear such a connection.
When a child is diagnosed with autism spectrum disorder, do their parents’ feelings about vaccines change in any way?
“We know that in recent years, rates of vaccination have been declining in general, and we wanted to determine whether this phenomenon proportionally affects children with autism spectrum disorder and their families,” Zerbo said.
He and his colleagues reviewed data on more than 3,700 children who had been diagnosed with autism spectrum disorder before age 5 and who had been born between 1995 and 2010. The researchers also looked at nearly 500,000 age-matched children without disorders.
Specifically, they looked at whether the children had received all the vaccines recommended by the US Centers for Disease Control and Prevention.
“What we found is that there are large disparities in vaccination rates between children with and without” autism spectrum disorders, Zerbo said. Comparing the two groups of children, “we found that 80% of children with autism received all vaccines recommended for children between ages 4 and 6, versus 94% among children without autism,” he said.
The researchers also examined the records from younger siblings of the children in the study: sisters and brothers born between 1997 and 2014.
Here, again, disparities were seen, as the younger siblings of children with autism were less likely to be fully vaccinated than siblings of children unaffected by autism, Zerbo said. For example, 73% of younger siblings of children affected by autism had been fully vaccinated by 11 months old, compared with 85% of younger siblings of children without autism spectrum disorder.