The anti-vaxxers are having a moment right now.

A month after he met with then-President-elect Donald Trump, Robert F. Kennedy Jr. — a fervent vaccine fear-monger — descended on Washington, DC, today with actor Robert De Niro to hold a press conference about vaccine safety.

The event was a showcase of some of the most thoroughly discredited claims about vaccines, from the notion that they cause autism, to the suggestion that vaccines are a huge source of mercury that’s making kids sick. Kennedy also suggested journalists and the government have been colluding to cover up the truth about vaccine safety, and that the shots have “caused the autism epidemic.”

Shortly after meeting with Trump in January, the environmental activist claimed he was invited to head a vaccine commission — a statement that sent the scientific community into a tizzy but was later denied by Trump’s spokespeople. They clarified that the president was instead looking at “the possibility of forming a committee on autism” but that no decisions had been made at that point.

Today, Kennedy said he expects the commission to go forward — and that he had talked to Trump’s team since their meeting — but he couldn’t confirm anything. In a conspiracy theorist’s flourish, he also said Trump told him “he knew that the pharmaceutical industry was going to cause an uproar” about it.

Routine vaccines for kids are now mercury-free. What’s RFK Jr. talking about?

Kennedy has a long history of stoking vaccine doubts, focusing in particular on the claim that the mercury in shots makes kids sick. As Vox’s Dylan Matthews has explained:

In 2005, he published an article titled "Deadly Immunity," in both Rolling Stone and Salon, alleging that the mercury-based chemical thimerosal, which was once but is no longer used as a preservative in children's vaccines, causes mercury poisoning and in turn autism. There is no evidence to support this view. The consensus position of the medical community is that thimerosal does not cause mercury poisoning in children, and in any case the symptoms for mercury poisoning and autism are radically different. A comprehensive review by a committee of the Institute of Medicine in 2004, the year before Kennedy's article, concluded that “the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism.”

Kennedy’s article at Salon was retracted, after the online magazine had to run a series of corrections that contradicted many of the piece’s claims.

What’s more, thimerosal, an ethyl mercury-containing antimicrobial, has been removed from most vaccines for children since 2001, with the exception of an inactivated flu vaccine. The public health community did this as a precautionary measure — part of a strategy to reduce mercury exposures from any source. And since then, researchers have found that autism rates among children haven’t gone down. So it’s not clear why Kennedy continues on this mercury and vaccines tirade. What’s more, thimerosal was never used in the measles-mumps-rubella vaccine that some vaccine skeptics claim causes autism.

“There is no link between thimerosal — mercury that was previously found in vaccines — and autism,” said Peter Hotez, a pediatrician and vaccine researcher at Baylor College of Medicine, who recently reviewed the evidence over at PLoS.

The only major thimerosal exposure to children is during maternal immunization with multidose flu vaccine, he added, but a large recent study in JAMA also found no link with autism. “Instead, beyond the overwhelming evidence of a genetic or epigenetic basis, we know there are certain chemical exposures during pregnancy that have been linked to autism. So I’m a bit baffled as to why Bobby Kennedy focuses on vaccines and autism, which has been debunked, instead of focusing on the known risks and demanding more research and studies,” Hotez said.

Robert De Niro, who has an autistic son, also has a history of anti-vax sympathy. Last year, the Tribeca Film Festival, which he co-founded, greenlit the screening of Vaxxed, an anti-vaccine film by the discredited physician-researcher Andrew Wakefield. Wakefield authored a retracted paper claiming the measles-mumps-rubella vaccine increases the risk of autism. The blowback from the scientific community was so fierce, De Niro withdrew the film from the festival — a move that was referred to as “censorship” at the event today.

De Niro and Kennedy’s press conference is more evidence that the anti-vax movement has been emboldened under Trump. As I explained in a feature story, we now have a president who courts known anti-vaccine crackpots and makes the same kinds of pseudoscience claims about lifesaving immunizations that they do. And vaccine researchers are now fearing the return of outbreaks of preventable diseases like measles and mumps at a time when more parents in many states are opting out of routine shots for their children.

Watch:: The 220-year history of the anti-vaccine movement