The controversial MMR jab does not cause autism, according to the largest ever study published on the issue.
The latest study, published in the journal Archives of Disease in Childhood, found no evidence of a link.
Professor David Salisbury, director of immunization at the U.K.'s Department of Health, said: "It's natural for parents to worry about the health and well-being of their children.
"I hope that this study will reassure them that there is no evidence linking the MMR vaccine to autism."
The new research contradicts two previous studies which had reported raised concentrations of measles antibodies in children with autism spectrum disorders (ASD).
Dr David Brown, from the U.K.'s Health Protection Agency, worked on the latest research.
He said: "The paper adds to the overwhelming body of evidence from around the world supporting the use of MMR."