Mercury-based vaccines and MMR jabs do not lead to an increased risk of autism, a Canadian study says.
Thimerosal is being phased out of vaccines
McGill University Health Centre looked at patterns between the development disorder and jabs in 28,000 children, the Pediatrics journal reported.
They found autism rates were higher in children given jabs after thimerosal was eliminated from vaccines and after MMR vaccination coverage decreased.
Experts said research was now needed to explain why autism was more common.
Concerns were raised in the late 1990s that the MMR jab may be linked autism as the three-in-one vaccine was said to overload the immune system.
The 1998 research has since been discredited, but immunisation rates have dropped in recent years.
Meanwhile, thimerosal, traditionally used as a preservative in vaccines, has been gradually phased out of use after being linked to autism.
This has come at a time when autism rates have been rising across the world.
Before the 1980s, one in 2,500 children was diagnosed as autistic, a developmental disability that affects the way a person communicates and interacts with others. Now the figure is closer to one in 250.
But the Canadian team said their study should help allay fears over the link, the journal reported.
The team found that after thimerosal was phased out in Quebec in 1996, the autism rate rose from 59.5 per 10,000 to 82.7 per 10,000.
And after MMR coverage fell in the late 1990s, the rate rose to 102.5 per 10,000 compared to 40.6 in the late 1980s.
Lead researcher Dr Eric Fombonne said: "There is no relationship between the level of exposure to MMR vaccines and thimerosal-containing vaccines and rates of autism.
"We hope this study will finally put to rest the pervasive believe linking vaccines with development diseases like autism."
And he added the rise in autism rates was likely to be caused by a broader definition of autism and greater awareness of the disorder.
Professor Simon Baron-Cohen, an autism expert at Cambridge University, said research was needed to pin down why there has been a rise in autism.
He said there was many likely factors but an "explanation" was needed.
"There may also be some as yet unidentified environmental factor, but the new study suggests MMR and thimerosal are ruled out."
Jackie Fletcher, from campaign group Jabs, a support network for parents who believe their children have been damaged by vaccines, said the study still did not prove there was not a link.
"What we need, and what we have always called for, is a full and open review into the link so we cann establish once and for all what the truth is."