Robert F Kennedy Jr has told anti-vaxxers they have a "friend in the White House". 

The US health secretary made the declaration at a conference of the Children's Health Defense, a non-profit activist group mainly known for anti-vaccine advocacy for which Mr Kennedy previously served as chair and chief legal counsel.

During his keynote speech at the event in Washington, Mr Kennedy told those in attendance that he was working to turn their priorities into policy.

"Let me be clear: You have a strong and steadfast friend in the White House," he said.

"We've accomplished in 19 months things that would have seemed unthinkable two years ago."

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Mr Kennedy also spoke about the Trump administration's moves to reduce the childhood vaccination schedule and reshape a key vaccine advisory board - measures that have since been halted by a judge.

He also praised the US president for his attempts to overhaul vaccine guidance, including an executive order last month which called for a spacing out the measles, mumps and rubella vaccine, defying recommendations from medical groups.

On its website, the Children's Health Defense says its mission is "to restore and protect the health of children by eliminating exposures to environmental toxins, holding responsible parties accountable, and establishing safeguards to prevent future harm to children's health".

A long-time anti-vaccine activist, Mr Kennedy chaired the group for several years and told attendees at the conference: "We have not taken vaccines away from anybody. We have preserved access.

"But we have started asking the questions that you and millions of American parents have been asking for years."

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'Fear and mistrust'

Mr Kennedy's speech comes as the US faces its worst year for measles in 35 years, and has seen seven reported measles-associated deaths in the last two years - more than the combined total of reported deaths over the previous three decades.

Josh Shapiro, the governor of Pennsylvania, where officials have reported four measles-associated deaths this year, accused Mr Kennedy of fuelling "fear and mistrust".

In a social media post, Mr Shapiro said the health secretary "chose to spend his time today addressing the premier vaccine-denial conference in America", where he "pushed a narrative that continues to stoke fear and mistrust".

Last year, Mr Kennedy and Mr Trump addressed what they described as a "meteoric rise" in cases of autism, suggesting the increase was linked to the use of Tylenol - an American-branded version of paracetamol - during pregnancy.

The comments were widely condemned by the scientific community, with UK health experts and officials pushing back on the claims, saying there is "no evidence" for it.