A new study of more than half a million children has found no link between the measles, mumps and rubella vaccination and autism.
The Danish study, published in the Annals of Internal Medicine journal today, looked at all children born in the country between 1999 and 2010. The children were followed through to the end of August 2013.
It found the MMR vaccine did not increase the risk of autism, even in children with other autism risk factors or in children whose siblings had autism.
There was also no clustering of autism cases following vaccination.
University of Otago Professor Michael Baker, who is based in Wellington, says the study was "very reassuring for any parents who are worried about the possible link".
He told Larry Williams that the study is about as good as you could get in studying these links.
"Scientists are very reluctant to ever say that there's definitive proof about anything, but I think this is about as close as you can get."
Researchers from Statens Serum Institut in Copenhagen found that of the 657,461 children included in the study, only 6517 were diagnosed with autism.
Of the children followed, 95 per cent received the first vaccination, which is offered at 15 months, but there was no difference in the number of vaccinated children with the disorder compared to the number of unvaccinated children.
Baker says that most scientists have believed this already.
"The only criticism was why are you studying something that is so improbable, and there are already so many studies showing there was no link."
He says that another piece of evidence to counter the sad legacy of the Wakefield study published more than 20 years ago, which only study a small number of children and relied on tenuous links.
"It's taken repeated bits of high quality work over 20 years that have all shown the same thing, that there's no associatoion.
Baker says that the study was withdrawn and the author has had his medical license revoked.
Claims of a link between the MMR vaccine and autism continued to cause concern among the medical community and challenge vaccine uptake.
There has been an increase in measles cases in Europe and the United States and the World Health Organisation has declared vaccine hesitancy as one of the top 10 threats to global health.
In New Zealand there have been a number of outbreaks in recent years. Yesterday, the Canterbury District Health Board confirmed seven people had contracted the disease in an outbreak which stretched back 11 days.
In January, at least six people in the Waikato contracted the disease.
During a major mumps outbreak in 2017 and early 2018, more than 1000 people, mostly in Auckland, contracted the disease.
Baker says that these diseases are very infectious, and you need very high vaccine coverage to ensure they cannot spread.
He said it was important everyone was vaccinated because it stopped the disease from spreading when brought into the country by travellers.
"We'll keep seeing measles cases in New Zealand until it's gone from the public."
A 1998 paper in the Lancet which first implied a link between the MMR vaccine and autism was retracted in 2010 but turned thousands of parents around the world against the vaccinations.
The film Vaxxed: From cover-up to catastrophe, which was released in 2016 and also claims there is a link between autism and the MMR vaccine, has also seen a growth in reluctance from many parents to have their children vaccinated against the diseases despite widespread criticism of faulty evidence.
Director of the Immunisation Advisory Centre and Associate Professor in the division of general practice and primary health care at the University of Auckland Nikki Turner said most of the current cases of measles in New Zealand were in young adults who were unaware they were not completely immunised when they were young.
"This is the legacy of a system that historically was not so effective at offering services, changed schedules often and does not have a national register for those who missed out," she said.
"There was some added effect from some vaccine hesitancy in the 1990s arising from the myth that arose from a mistaken belief in association with childhood autism."