Researchers have shown there is no link between the MMR jab and autism.
The jab protects against mumps, measles and rubella
It comes after a controversial study in 1998 suggested there was, prompting a drop in the up-take of the vaccine.
What is MMR?
MMR is a combined vaccine against measles, mumps and rubella, three common infectious diseases of childhood.
It was introduced in the UK in 1988 to replace single vaccines for each disease.
It is used in countries throughout the world, with millions of doses delivered each year.
Babies are given the first dose of MMR when they are around 13 months old and
the second jab between the ages of three and five to give them maximum immunity.
Why are people worried about it?
In 1998, a study published in the respected journal The Lancet suggested the jab may be linked to autism and bowel disease.
The paper and the media furore that followed it prompted many parents to decide against having their children vaccinated with the three-in-one jab.
Some opted to have their children vaccinated using single vaccines for each disease. However, others decided against having their children vaccinated against these diseases at all.
Mumps, measles and rubella are all serious diseases. Many doctors are concerned that a drop in vaccination levels could leave many children at risk.
What do other experts say?
The UK government and the vast majority of scientists insist that the three-in-one jab is safe.
No research has been published to back up claims that it may be linked to autism and bowel disease.
There have been many studies examining the safety of MMR since 1998. All have concluded that the three-in-one jab is safe.
Many of these have used population studies to monitor trends in autism, but the latest study analysed blood samples to see if the jab prompted an immune response that could have triggered autism.
The team found no difference between the children with autism and those without.
And it comes after The Lancet, which published the controversial MMR paper in the first place, publicly announced in 2006 that it should never have printed it.
It says the study was flawed and that Dr Andrew Wakefield, the lead author, had a serious conflict of interest.
Dr Wakefield insists he has done nothing wrong and that the science behind his study is still valid.