The belief that routine childhood vaccines can lead to autism remains one of the most stubbornly enduring.

The mainstream medical community insists there is no evidence to support the theory, and cite study after study that have found no link. Yet the Internet is filled with groups and organizations who insist that vaccines are causing children to become autistic.

The controversy returned to the headlines this week, when the American Academy of Pediatrics issued a call for ABC to cancel the debut episode of "Eli Stone," a new legal drama that also airs on CTV.

The episode featured a lawyer who argued in court that a vaccine caused a child's autism. The episode ends with the jury awarding the mother US$5.2 million after it is revealed the CEO of the vaccine-maker kept his own daughter from getting the company's vaccine because of autism concerns.

The AAP, which represents 60,000 U.S. pediatricians, noted that while the show included statements that numerous studies have refuted any link between autism and vaccines, the episode's conclusion leaves audiences "with the destructive idea that vaccines do cause autism."

ABC chose not to cancel the episode, but ran a disclaimer at the opening of the show stating the story is fictional. A message at the end referred viewers to a U.S. Centers for Disease Control website for information about autism.

The AAP has long campaigned against the misinformation linking vaccines to autism and has even dedicated a section of its website to clarify its position on the controversy. So how did this debate begin?

Study ignites controversy

It started in February, 1998, in the highly prestigious, British-based medical journal, The Lancet. There, British gastroenterologist Dr. Andrew Wakefield, along with 12 co-authors, published a small study on 12 children in which he claimed to have found a link between inflammatory bowel disease, autism and the measles-mumps-rubella vaccine introduced across the U.K. in 1988.

Most agreed that further research was needed and that parents should continue to have their children vaccinated with MMR. But, in the huge media feeding frenzy that followed, Wakefield suggested that parents should stop taking the vaccine and opt instead for each vaccine on its own.

That led to an almost immediate drop in immunization rates. Within a few years, MMR vaccination rates sunk to 75 per cent in Britain, well below the 95 per cent authorities say is needed to keep these diseases from circulating.

While the rate has since climbed to about 85 per cent, Britain continues to suffer outbreaks of these three diseases. In fact, it's suspected that a recent widespread outbreak of mumps in Canada was sparked by a single infection from Britain. And in March, 2006, a 13-year-old boy who had not been given the MMR vaccine became the first person in Britain in 14 years to die of measles.

Wakefield's research was attacked as flawed almost from the beginning. In fact, even his collaborators changed their minds. In 2004, 10 of Wakefield's 12 co-authors retracted their conclusions in the Lancet study. They stated:

"We wish to make it clear that in this paper no causal link was established between (the) vaccine and autism, as the data were insufficient. However the possibility of such a link was raised, and consequent events have had major implications for public health. In view of this, we consider now is the appropriate time that we should together formally retract the interpretation placed upon these findings in the paper, according to precedent."

Shortly before publishing the retraction, Lancet editor Dr. Richard Horton declared Wakefield had a "fatal" conflict of interest that his team was not aware of. Wakefield was doing paid research for a group of parents of autistic children who were trying to mount a class-action suit against the makers of the MMR vaccine.

Conflicts of interest?

Had his team known about those conflicts, Horton said he would never have published the study.

But even while Wakefield's theory on the cause of autism was losing credibility, a revised theory was emerging.

In 2003, David and Mark Geier, a father-and-son research team began publishing studies in a number of small journals in which they reported finding an association between thimerosal-containing vaccines and autism. They concluded that it wasn't the vaccines itself causing the illness, but the mercury-based thimerosal, which is used as a preservative.

The Geier studies might have been ignored if not for the fact that a few years earlier, in 1999, the Centers for Disease Control (CDC) and the American Academy of Pediatrics (AAP) asked vaccine-makers to remove thimerosal from vaccines as quickly as possible. This move came after they realized that since 1991, children receiving routine vaccines had been getting amounts of thimerosal that might push them over accepted levels of mercury.

The move was said to be simply cautionary. But it sparked confusion and led some to declare there had been a government cover-up of a widespread health risk. Shortly after, the lawsuits against vaccine-makers was launched.

The debate moved mainstream when such celebrities as Jenny McCarthy and Bobby Kennedy Jr. began insisting that the link between vaccines and autism was clear and that vaccine-makers were refusing to accept responsibility.

Since then, numerous large, peer-reviewed studies have been published that have found no link. The most recent was published just this week in the the Archives of Disease in Childhood, one of the journals of the British Medical Journal.

It looked at nearly 100 autistic children and 52 with learning difficulties from a sample of 57,000 children in southern England had received an MMR vaccination. 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.

And earlier this year, researchers from the California Department of Public Health Autism found that the reporting of autism cases in that state continued to climb even after from 1995 to 2007 -- long after thimerosal was removed from routine childhood shots. Doctors noted that if the vaccines really were causing autism, rates should have dropped.

Despite the many studies pouring cold water on the anti-vaccine side, the debate continues 10 years later, with dozens of websites across the Internet encouraging parents to refuse to allow their children to be vaccinated.

Sadly, while the voices of those parents who have defied general medical advice ring loud, the voices of those parents who have watched their children die or become disabled from such diseases as polio, meningitis, and hepatitis are rarely heard. Vaccination has been called the single greatest medical intervention over the past century and has saved so many lives that most of us have never seen the diseases they prevent. Yet, many parents still choose not to vaccinate their children.

Since his 1998 study, Wakefield has lost his position with the British National Health Service and now works for a non-profit centre for autistic children in Texas, called Thoughtful House. While he continues to assert that the results of his 1998 study are still valid, the General Medical Council, the British body that investigates alleged malpractice by doctors, decided to take action.

This past July, the GMC began hearings into allegations that Wakefield and two colleagues behaved unethically and dishonestly in conducting their research. The hearings had been expected to last months but after the prosecution case was presented, the panel suspended proceedings and defence presentation until March, 2008.

Shortly before those hearings began, Wakefield agreed to an interview with U.K.'s The Observer, which he ended by declaring: "My colleagues and I won't be deflected by the interests of public health policymakers and pharmaceuticals. I want to help children with autism; they are my motivation. If the work ultimately exonerates the vaccines, that's fine. If not, we need to think again."