A mistaken belief that the measles, mumps and rubella (MMR) vaccination will lead to autism may be behind outbreaks of measles in Europe and the US.
The Mayo Clinic's Dr Gregory Poland has called for doctors, the media and the public to become better educated about the range of research that has shown there is no connection between the jab and autism in children.
He explained a 1998 study suggesting a link - which was retracted after the British General Medical Council found it to be fraudulent - has had a devastating effect, despite over 20 pieces of research spanning two decades failing to find evidence of an association.
"A rising portion of the population is deciding not to immunise their children because of this controversy and these children are now susceptible to the measles virus," said Dr Poland.
Earlier this month, the Western Mail suggested parents in Wales may be becoming more trusting of the MMR jab, as the number of children receiving it is at its highest level since the controversy first emerged.