The vast majority of scientists stand behind the safety of the combined measles, mumps and rubella vaccine, but the tendency of reporters to give equal space to both sides of the debate meant many people thought there was equal evidence for each view, said Professor Justin Lewis and colleagues.

The researchers from Cardiff University's journalism and media school polled more than 1,000 people twice during 2002, once in April and again in October. They also monitored MMR coverage in two television news programs, nine newspapers and one radio program between January and September of the same year.

In the October survey, 53 percent of people wrongly said there was equal evidence on both sides of the debate, and only 23 percent correctly thought the weight of evidence suggests there is no link between the MMR vaccine and autism.

"Attempts to balance claims about the risks of the MMR jab tended merely to indicate that there were two competing bodies of evidence," the researchers said in their report, which was published by the Economic and Social Research Council.

In reality, they say, the suggestion made by Dr. Andrew Wakefield in 1998 linking the vaccine to autism has not been supported by other studies.

The researchers asked whether journalists ought to subject the claims of "maverick" scientists like Wakefield to closer scrutiny before reporting them. Largely, the British public agreed.

Forty-eight percent of those surveyed felt that if a scientist makes claims that go against the great majority, the media should wait until the findings are confirmed before reporting them.

On the other hand, 34 percent felt that research like Wakefield's should be given "prominent coverage because it is news."

"While Wakefield's claims are of legitimate public interest, our report shows that research questioning the safety of something that is widely used should be approached with caution, both by scientists and journalists," said Lewis.

"This is especially the case where any decline in confidence can have serious consequences for public health. The research also has implications for the debate about fairness in journalism, suggesting that legal definitions of impartiality in broadcast journalism should not be interpreted in a simplistic fashion."