Robert De Niro has claimed "there is a link" between vaccines and autism as he defended a controversial documentary about the subject.
The Oscar-winning actor said his wife believes their 18-year-old son Elliot, who has the condition, changed overnight after having a vaccination.
Robert, 72, said he now partly regrets axing an anti-vaccine documentary from the Tribeca Film Festival, which he co-founded in New York.
The film, Vaxxed: From Cover-up To Catastrophe, is directed by former UK doctor Andrew Wakefield, who was struck off the British medical register over widely discredited claims about the Measles, Mumps and Rubella (MMR) vaccine.
Robert said he was "not so sure" about the film-maker but encouraged people to watch the documentary.
He told NBC's Today show: "I, as a parent of a child who has autism, am concerned. I want to know the truth.
"I'm not anti-vaccine, I want safe vaccines. There are many people who will come out and say: 'I saw my child change overnight. I saw what happened. I should have done something and I didn't.' There's more than this than meets the eye."
Asked whether his son changed overnight after having the vaccine, he replied: "My wife says that. I don't remember. My child is autistic and every kid is different. There's something there that people aren't addressing.
"For me to get so upset ... it means there's something there."
Robert said he believed the issue was "much more complicated" than the scientific consensus that the MMR jab is not linked to autism.
He added that the vaccine was "dangerous to certain people who are more susceptible".
"There is a link and they're saying there isn't," he said.
"I'm not a scientist but I know because I've seen so much reaction. Let's just find out the truth.
"There are some people who cannot take a vaccine and they have to be found out and warned that you don't just give a kid a bunch of shots and then something happens."