“President-elect Trump has some doubts about the current vaccine policies and he has questions about it,” Robert F. Kennedy Jr. said after his meeting. | Getty Vaccine skeptic RFK Jr. says he'll chair vaccine commission for Trump

President-elect Donald Trump has asked Robert F. Kennedy Jr., a major source of disproved theories imputing harm to vaccines, to chair a “commission on vaccine safety and scientific integrity,” Kennedy told reporters after a meeting in Trump Tower on Tuesday.

Kennedy, who said he accepted the assignment, has been insisting for over a decade that traces of mercury in a preservative formerly used in childhood vaccines caused a massive increase in autism diagnoses. He has clung to the theory despite overwhelming scientific evidence to the contrary.

Later in the day, however, Trump appeared to be backing off Kennedy’s report. In a statement released by the transition team, Trump said he “enjoyed his discussion” with Kennedy and was “exploring the possibility of forming a committee on Autism, which affects many families; however no decisions have been made at this time.”

Kennedy and other vaccine skeptics have found a welcoming audience in Trump, who has repeatedly stated the belief that vaccines cause autism.

“President-elect Trump has some doubts about the current vaccine policies and he has questions about it,” Kennedy said after his meeting, which he said Trump requested. It's one of several meetings that Trump has held with anti-vaccine leaders in recent months.

Both Trump and Kennedy contend that they are not “anti-vaccine.” However, since they question the vaccines that have been given to children in the United States and the rest of the world for decades, it is hard to otherwise characterize their positions.

Kennedy and other anti-vaxers say a vast array of CDC, FDA and pharmaceutical industry officials have covered up evidence of vaccine damage. Independent research has found no evidence this is true.

“His opinion doesn't matter, but the science does matter and we ought to be reading the science and we ought to be debating the science," Kennedy said. "And that everybody ought to be able to be assured that the vaccines that we have — he's very pro-vaccine, as am I — but they're as safe as they possibly can be.”

In statements on Twitter and during the campaign, Trump promoted the idea that vaccines are dangerous. During an early GOP debate, Trump said he believed in the autism link, and he met in August with British physician Andrew Wakefield, proponent of the idea that CDC has covered up pharmaceutical industry poisoning of the brains of millions of children.

“[Y]ou take this little beautiful baby, and you pump — I mean, it looks just like it’s meant for a horse, not for a child,” Trump said in a September 2015 GOP debate when he again cited the discredited link between vaccines — or vaccine dosing schedules — and autism.

"If I were President I would push for proper vaccinations but would not allow one time massive shots that a small child cannot take - AUTISM," he tweeted in 2014.

One transition adviser Scott Gottlieb, widely seen as a potential Trump pick for FDA, has often taken on the "anti-vaxers" and defended vaccines' public health value.

Vaccination proponents were crushed to learn that Trump asked Kennedy to investigate vaccine safety. They called Trump's request a pointless exercise that could lead parents to skip their children’s shots and cause outbreaks of deadly diseases like measles and whooping cough.

“Robert Kennedy's history of ignoring vaccine research and science makes him not only ill-prepared to head a commission on vaccine safety, but also raises the likelihood that this commission will do more harm than good,” said Deborah Wexler, executive director of the Immunization Action Coalition.

Jason Millman contributed to this report.