On Monday President Trump and the U.S. Health Secretary Robert F. Kennedy Jr. held a press conference in which they made extraordinary new claims about autism. They suggested a potential link between the use of Tylenol during pregnancy and the development of autism. They also advocated spacing out childhood vaccinations.

The two men's interest in the link between vaccines and autism goes back decades but these claims did not originate in the US. They trace back to the UK in 1998, when disgraced former doctor Andrew Wakefield first published his now-debunked theory linking MMR vaccines to autism cases in children.

Today on the Global Story science journalist Adam Rutherford explains how the Wakefield vaccine conspiracy became the biggest medical disinformation disaster in recent history, and how these ideas found fertile ground in the Trump administration.

Producers: Viv Jones, Valerio Esposito

Image: President Donald Trump, in front of U.S. Secretary of Health and Human Services Robert F. Kennedy Jr., delivers remarks linking autism to childhood vaccines and to the use of popular pain medication Tylenol for pregnant women and children, claims which are not backed by decades of science, at the White House. REUTERS/Kevin Lamarque