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.”

In a sample of communities, the biennial autism surveillance report found that 1 in 31 8-year-olds had the condition. The CDC attributed the increase to better screening.