Kennedy is the chairman of the World Mercury Project (WMP), a nonprofit public advocacy organisation campaigning for mercury to be excluded from vaccines.

The actor was in attendance as Kennedy reportedly said onstage vaccines have “caused the autism epidemic” and blamed journalists and the government for hiding the real truth about vaccine safety, according to Vox.

Environmental activist Kennedy has claimed he is not anti-vaccine, but rather, he is in favour of “safe vaccines.”

“I’m glad I’m here. I thought what Bobby (Kennedy) said was great. It was eloquent. I couldn’t have said it better myself. I agree with him 100 percent. Thank you,” the Goodfellas star expressed, affirming his support for his panellist.

The 73-year-old actor's attendance comes after he revealed last year (16) his teenage son Elliot has autism. And at his Tribeca Film Festival in 2016 the Hollywood icon gave the go-ahead to screen the controversial documentary Vaxxed, by discredited physician Andrew Wakefield. However, after immense backlash from the scientific community the screening was pulled.

Wakefield published his first study linking vaccines to autism in 1998, but was unable to prove his theory, and the study was withdrawn and his paper discredited.

De Niro still defended the film after it was dropped from the festival, telling the Today show at the time, “I think the movie is something that people should see.”