MMR vaccine not seen causing autism

LONDON (Reuters) - A vaccine for measles, mumps and rubella does not cause autism, according to the largest study yet showing there is no evidence linking the childhood shot to the development disorder.

The study, published on Tuesday in the Archives of Disease in Childhood, found no evidence of any abnormal biological response from the shot that could point to a link between the vaccine and autism.

"This study really supports the view these are safe vaccines," said David Brown, a researcher at Britain's Health Protection Agency who worked on the study. "The evidence is now so solid there really isn't a need for further studies here."

In 1998, Dr. Andrew Wakefield of Royal Free Hospital in London and colleagues sparked a fierce worldwide debate among scientists and a health scare by suggesting the MMR jab caused autism. Outbreaks of all three diseases followed.

Autism is marked by a variety of difficulties in social interaction and behavior, from the awkwardness of Asperger syndrome to severely debilitating repetitive behaviors and an inability to speak.

The British study looked at nearly 100 autistic children, a group of 52 with learning difficulties and 90 who were developing normally.

All the volunteers chosen from a sample of 57,000 children in southern England had received an MMR vaccination but not everybody got both doses, said Gillian Baird, a pediatrician at the Newcomen Centre for Child Development, who led the study.

The researchers took blood samples from the children and found no abnormal immune response in any of them marked by higher antibody levels or presence of a measles virus still left in the body from the shot, Baird added.

Wakefield, whose research has been widely discredited, had pointed to these two factors as a way to explain the link but the latest findings do not back up that case, Baird said. Wakefield said in a newspaper interview last year he believed it was biologically plausible the shot could cause autism.

"There was no difference across any of the groups no matter how you cut them up," Baird said in a telephone interview. "The response to the MMR vaccine was the same in every group."

Before Wakefield's study, more than 90 percent of British children received the vaccination, a figure that dropped to 80 percent before recovering to a current 85 percent, according to government figures.

Baird said she hoped the findings, along with a U.S. study last week showing that a mercury-based preservative called thimerosal did not cause autism, would bolster confidence in the MMR shot.

"It is a big study and we hope people can have confidence in the MMR shot again," Baird said in a telephone interview. "Measles has come back again because people have stopped immunizing their children."

(Reporting by Michael Kahn, Editing by Maggie Fox)