Robert F. Kennedy Jr., a proponent of a widely discredited theory that vaccines cause autism, said Tuesday that President-elect Donald Trump asked him to chair a new commission on vaccines.
Hours later, however, a spokeswoman for Trump's transition said that while Trump would like to create a commission on autism, no final decision had been made.
If Trump follows through, the stunning move would push up against established science, medicine and the government's position on the issue. It comes after Trump - who has long been critical of vaccines - met at Trump Tower with Kennedy, who has spearheaded efforts to roll back child vaccination laws.
"The President-elect enjoyed his discussion with Robert Kennedy Jr. on a range of issues and appreciates his thoughts and ideas," Trump transition spokeswoman Hope Hicks said in a statement. "The President-elect is exploring the possibility of forming a commission on autism, which affects so many families; however no decisions have been made at this time.
"The President-elect looks forward to continuing the discussion about all aspects of autism with many groups and individuals," she added.
Speaking to reporters earlier Tuesday in the lobby of Trump Tower in New York, Kennedy said that Trump called him to request the meeting and that he accepted the offer of a position on the commission during the meeting.
"President-elect Trump has some doubts about the current vaccine policies, and he has questions about it," Kennedy said. "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.
"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," he added.
There is a federal advisory committee on immunization, made up of medical and public health experts who develop recommendations on how vaccines are used in the United States.
The announcement was met with alarm from health professionals who say that putting a proponent of a conspiracy theory in a position of authority on the issue is dangerous.
"That's very frightening; it's difficult to imagine anyone less qualified to serve on a commission for vaccine science," said Peter Hotez, dean of the National School of Tropical Medicine at Baylor College of Medicine and president of the Sabin Vaccine Institute, a nonprofit that works to control, treat and eliminate vaccine-preventable and neglected tropical diseases.
"The science is clear: Massive evidence showing no link between vaccines and autism, and as both a scientist who develops vaccines for poverty-related neglected diseases and the father of an adult daughter with autism, there's not even any plausibility for a link," Hotez continued. "Autism is a genetic condition."
"Our nation's public health will suffer if this nascent neo-antivaxxer movement is not stopped immediately," he added.
Kennedy has been a proponent of nonmedical exemptions for parents who seek to prevent their children from being vaccinated, which is mandatory in most states.
He has argued that mercury-based additives in vaccines explain the link to autism. And he has alleged that government scientists, journalists and pharmaceutical companies have colluded to hide the truth from the public.
"They get the shot. That night they have a fever of 103. They go to sleep, and three months later their brain is gone," Kennedy said at the premiere of an anti-vaccination film screening in California in 2015. "This is a holocaust, what this is doing to our country."
Kennedy is known to be an occasional conspiracy theorist and longtime opponent of mandatory vaccination laws. In 2006, he wrote in Rolling Stone magazine that the Republican Party had stolen the 2004 election from Democratic candidate John Kerry. At a 2013 speech in Dallas, he said he doesn't believe the lone gunman theory of the assassination of his uncle, President John F. Kennedy.
Trump notably expressed support for the theory that vaccinations are linked to autism at a Republican presidential debate in 2015.
"We had so many instances, people that work for me, just the other day, 2 years old, a beautiful child, went to have the vaccine and came back and a week later got a tremendous fever, got very, very sick, now is autistic," Trump said.
The comments were widely denounced by medical professionals who say that there is no evidence that vaccines lead to autism. In fact, the study that popularized the idea has been retracted and discredited as fraudulent. Multiple high-quality studies have found no link between vaccines and autism.
Trump's claim was rejected on the same debate stage by retired neurosurgeon Benjamin Carson, whom Trump has now nominated to serve as his secretary of housing and urban development.
"The fact of the matter is we have extremely well-documented proof that there's no autism associated with vaccinations," Carson said.
The controversy began in 1998 after The Lancet, a respected medical journal, published a paper by researcher Andrew Wakefield and colleagues linking the measles, mumps and rubella vaccine to autism. It had a sample of only 12 subjects and speculative conclusions but launched a global movement joined by celebrities including Jenny McCarthy and Jim Carrey, who warned parents to stop vaccinating their children. A drop in MMR vaccinations followed.
But the study was a fraud. The Lancet determined that Wakefield had been funded by attorneys for parents who had brought lawsuits against vaccine companies. In 2010, the journal retracted the paper. Wakefield was stripped of his medical license. Large studies that examined whether there is an association between vaccines and autism, including one that examined 96,000 U.S. children, found none.
The Centers for Disease Control and Prevention has said flatly that there is no link between vaccines and autism and that vaccine ingredients do not cause autism. Scores of studies from around the world since then have shown conclusively that vaccines do not cause autism. Every relevant scientific and medical organization has examined the evidence and concluded that vaccines are safe and effective and that the real danger lies in skipping or delaying them.
Still, the theory has retained its adherents. The United States has experienced recent measles outbreaks linked to unvaccinated residents, including one in 2014 that infected 383 people, most of them in Amish communities in Ohio. In 2015, another multistate outbreak was linked to California's Disneyland theme park. In both years, the source of the infection was believed to be people who brought the virus home after visiting the Philippines.
In tweets as early as 2012, Trump expressed skepticism about vaccines, and in 2014 he said that "doctors lied" about vaccines. In other tweets, Trump has referred to vaccines as the cause of "doctor-inflicted autism."
"Massive combined inoculations to small children is the cause for big increase in autism," Trump said in an August 2012 tweet.
At the presidential debate in 2015, he claimed that his children had been vaccinated in small doses.
"I am totally in favor of vaccines, but I want smaller doses over a longer period of time," Trump said. "Because you take a baby in, and I've seen it. I've had my children taken care of over a long period of time, over a two- or three-year period of time."
Trump's statements at the Republican debate in 2015 were denounced as "false" by the American Academy of Pediatrics, which released a strongly worded condemnation.
"Claims that vaccines are linked to autism, or are unsafe when administered according to the recommended schedule, have been disproved by a robust body of medical literature," said Karen Remley, executive director of the AAP. "It is dangerous to public health to suggest otherwise."
"There is no 'alternative' immunization schedule. Delaying vaccines only leaves a child at risk of disease for a longer period of time; it does not make vaccinating safer. Vaccines work, plain and simple," she added.
Autism is now considered a spectrum of brain disorders with a multitude of causes. According to Autism Speaks, people with the disorder can have trouble with social interaction, verbal and nonverbal communication and repetitive behaviors. One in 68 U.S. children are considered to be on the autism spectrum - a tenfold increase from 40 years earlier, largely due to changes in how autism is defined and diagnosed.
The Washington Post's Mark Berman contributed to this report.