Kennedy, Hotez says, made a “false statement” in claiming that the scientific community denies that there are any environmental factors at play. “I’ve said to RFK Jr. that there could be an environmental component, but not vaccines, because autism occurs in fetal brain development well before kids ever see vaccines.”

A new study from the US Centers for Disease Control and Prevention shows that the autism diagnosis rate has increased among US children, continuing a long-term trend that experts have largely attributed to better understanding of and screening for the condition.