The childhood vaccine that wards off mumps, measles and rubella does not increase the risk of autism, a new Danish study shows.
Anti-vaxxers have long claimed the MMR vaccine can cause autism but researchers who studied more than 650,000 babies born in Denmark over 11 years found there is absolutely no association.
The vaccine does not increase the risk of autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination, they found.
The study is yet another piece of evidence to debunk claims by anti-vaxxers that vaccinations are dangerous and can leave children with life-long challenges.
Those theories have been blamed for a drop off in vaccination rates in some places around the world, exposing kids to childhood diseases that are known to kill and cause permanent disabilities.
Researchers from Denmark's Statens Serum Institut looked at 657,461 children born between 1999 and 2010. Of those, 6,517 were diagnosed with autism.
They found no difference in autism rates when they compared children who had the vaccine, with those who had not.
Australian experts hope the study will stop the MMR myth from being propagated online.
"Over 20 years have passed since the publication of a controversial Lancet paper that turned a number of parents around the world against the MMR vaccine due to an implied link with autism," says Dr Hannah Kirk from the Monash Institute of Cognitive and Clinical Neurosciences.
That paper, which included just 12 children, was later retracted because of errors, but myths around the vaccine continue to be shared.
"It is fantastic to see another high-quality study refute the myth of an autism and MMR vaccine link," she said.
"(But) it is disappointing that substantial research efforts, time and funds have to continue to be directed toward disproving something that we already know to be incorrect; rather than investigating more accurate causes of autism."
The study has been published in the journal Annals of Internal Medicine.
Australian Associated Press