Among the sites, there were large differences. Prevalence ranged from 9.7 per 1,000 children who were 8 years old in Texas (Laredo) to 53.1 in California. These differences are likely due to “differences in availability of services for early detection and evaluation and diagnostic practices,” the CDC and network researchers wrote.

For instance, California—the site with the highest prevalence among 8-year-olds and also 4-year-olds—has a local initiative called the Get SET Early model. “As part of the initiative, hundreds of local pediatricians have been trained to screen and refer children for assessment as early as possible, which could result in higher identification of ASD, especially at early ages,” the authors write. “In addition, California has regional centers throughout the state that provide evaluations and service coordination for persons with disabilities and their families.”

On the other hand, the low ASD rates at the network’s two Texas sites could “suggest lack of access or barriers to accessing identification services,” the authors say. The two Texas sites included primarily Hispanic and lower-income communities.

The newly revealed higher rates in some of the network’s underserved communities could link ASD prevalence to social determinants of health, such as low income and housing and food insecurity, the authors say. Other factors, such as higher rates of preterm birth, which is linked to neurodevelopmental disabilities, as well as lead poisoning and traumatic brain injuries, may also contribute to disparities.

Anti-vaccine voices

The detailed, data-heavy report stands in contrast to the position of health secretary Robert F. Kennedy Jr., a longtime anti-vaccine advocate who promotes the false and thoroughly debunked claim that autism is caused by vaccines. Last month, Kennedy hired the discredited anti-vaccine advocate David Geier to lead a federal study examining whether vaccines cause autism, despite numerous high-quality studies already finding no link between the two.

Geier, who has no medical or scientific background, has long worked with his father, Mark Geier, to promote the idea that vaccines cause autism. In 2011, Mark Geier was stripped of his medical license for allegedly mistreating children with autism, and David Geier was fined for practicing medicine without a license.

In a media statement Tuesday in response to the new report, Kennedy called autism an “epidemic” that is “running rampant.” He appeared to reference his planned study with Geier, saying: “We are assembling teams of world-class scientists to focus research on the origins of the epidemic, and we expect to begin to have answers by September.”