Ten of 13 authors of a 1998 paper linking the childhood MMR vaccine to austism retracted their conclusions, in part because the selection of subjects may have been biased and because one author recevied undeclared funds from a group pursuing legal action on behalf of children allegedly damaged by the vaccine.

"We wish to make it clear that in this paper no causal link was established between MMR vaccine and autism as the data were insufficient," the researchers wrote. "However, the possibility of such a link was raised and consequent events have had major implications."

A few years ago The Lancet, a well-respected medical news bulletin, published a paper suggesting the measles, mumps and rubella vaccine, MMR, might contribute to the development of autism.

The paper, according to The Lancet itself, is now known to be deeply flawed. The main author was being paid by lawyers who were trying to sue the vaccine manufacturers.