For millions of families, it was a possible answer for their children's struggles. Now, a landmark medical study concerning autism is being called a fraud.
Despite being stripped of his medical license, the doctor accused of wrongdoing continues to defend his research.
Dan and Kelly Lacek never had their youngest son vaccinated, afraid he would it could result in autism. Then, four years ago Matthew became severely sick.
"To find out that it's been a fraud and it's a conscious effort to mislead people, that's frustrating," says Mr Lacek.
"An elaborate fraud" is what the British Medical Journal is now calling the 1998 study by Dr Andrew Wakefield that claimed a link between the measles mumps rubella (MMR) vaccine and autism.
Last year a disciplinary panel found Dr Wakefield had presented his research in an irresponsible and dishonest way and the study was retracted.
Dr Wakefield claimed that eight children developed autistic symptoms within, on average, a week after receiving the MMR shot.
"I think what Dr Wakefield did was a moral crime, if not an actual crime," says investigative journalist Brian Deer.
By comparing the actual medical records of the children, Mr Deer says he discovered Dr Wakefield falsified data. That, in fact, some of the children had actually developed symptoms before vaccination, some were deemed normal months afterward and some never had autism at all.
Dr Wakefield appeared on CNN to defend himself.
"The studies are not a lie. The results have been replicated in five countries around the world."
And he still has his supporters, including celebrities such as Jenny McCarthy, though others claim Dr Wakefield has caused irreparable damage.
One fact that's not in dispute however: immunisation fates for the MMR shot have never fully recovered.
"There is absolutely nothing we do for our children that has more proven health benefit than getting them fully vaccinated on time," says Dr Richard Besser, senior health editor for ABC News.
The investigative reporter claims Dr Wakefield's motivation might have been money. Dr Wakefield was paid around $750,000 for his research by lawyers who were trying to sue the makers of the measles vaccine.
AP / RadioLIVE / 3 News