PRESIDENT-ELECT Donald Trump’s transition team tried to tamp down the report from leading vaccine skeptic Robert F. Kennedy Jr. that Mr. Trump had asked him to lead a new panel on the safety of childhood inoculations. The president-elect, we were told, is only exploring the possibility of forming a government commission on autism. But by even entertaining the idea, Mr. Trump — who has his own troubling history when it comes to vaccine safety — gives new life to debunked conspiracy theories tying autism to vaccines. That in turn endangers children’s lives.

Mr. Trump met Tuesday with Mr. Kennedy, a longtime opponent of mandatory vaccination laws who once characterized the shots children receive to guard against illness as a holocaust. The meeting at Trump Tower, which Mr. Kennedy told reporters was requested by Mr. Trump, caused immediate and understandable concern in the medical community.

“It gives it a quasi-legitimacy that I frankly find frightening,” William Schaffner, a professor of preventive medicine and infectious diseases at Vanderbilt University, told the New York Times. Theories about a link between vaccines and conditions such as autism have been thoroughly discredited in numerous scientific studies that have established — without any question — the safety of vaccines.

Yet Mr. Trump, 10 days away from taking the oath of office for president, thought it important enough to meet with a leading proponent of conspiracy theories about vaccines, someone who, by the way, holds a law — not a medical — degree. Mr. Trump’s past comments about vaccines — “massive combined inoculations to small children is the cause for big increase in autism,” he tweeted in 2012 — betray an ignorant distrust of vaccines.

If Mr. Trump wants to make attacking autism a priority, he should be applauded. But he needs to go about it responsibly. Experts will tell him that the diagnosis of autism is more prevalent than in the past not because there is an “epidemic,” as he once claimed, but because the definition of autism spectrum disorder has grown more inclusive. And they will assure him there is no connection to vaccines. He will endanger the health of millions of children if he fans doubts about vaccine safety.