(CNN) The measles, mumps, and rubella vaccine does not increase the risk of autism and does not trigger autism in children who are at risk, according to a new study of over 650,000 children.
Researchers used a population registry to evaluate whether the MMR vaccine increased the risk of autism in children born in Denmark between 1999 and 2010. A total of 657,461 children were followed through August 2013, with the researchers documenting diagnoses of autism spectrum disorder as well as known risk factors including age of the parents, diagnosis of autism in a sibling, preterm birth and low weight at birth.
Over 95% of the children received the MMR vaccine, and 6,517 were diagnosed with autism. The MMR vaccine did not increase the risk of autism in children who were not considered at risk for the disorder and did not trigger it in those who were, according to the study, published Monday in the journal Annals of Internal Medicine.
"This idea that vaccines cause autism is still around and is still getting a lot of exposure in social media," noted Anders Hviid, lead study author and senior investigator at Statens Serum Institut in Denmark.
With anti-vaccine groups becoming more vocal and even celebrities and politicians spreading fear of vaccines, Hviid and his team wanted to provide solid scientific answers.
The biggest contribution of the study was the inclusion of children at risk of autism, said Dr. Paul Offit, director of the Vaccine Education Center at Children's Hospital of Philadelphia, who was not involved in the new research. He hopes the latest piece of evidence will reassure families with young children at risk of developing autism spectrum disorder that the vaccine will not increase that risk.
The myth linking vaccines and autism grew out of a 1998 study by Andrew Wakefield, published in the medical journal The Lancet. Wakefield had been compensated by a law firm intending to sue manufacturers of the MMR vaccine, and in 2010, he lost his medical license. In 2011, The Lancet retracted the study after an investigation found that Wakefield altered or misrepresented information on the 12 children who were the basis for the conclusion of his study.
Several subsequent studies trying to reproduce the results have found no link between vaccines and autism.
"At this point, you've had 17 previous studies done in seven countries, three different continents, involving hundreds of thousands of children," Offit said. "I think it's fair to say a truth has emerged."
Yet the myth of a link between vaccines and autism continues to be used by anti-vaccine activists, who have been blamed for the ongoing measles outbreaks across the United States.
At least 206 US cases of measles have been recorded in 2019, after 372 cases in 2018, according to the US Centers for Disease Control and Prevention.
Around the world, measles cases increased by 48.4% between 2017 and 2018, according to UNICEF calculations from World Health Organization data. Ten countries, including Brazil, the Philippines and France, accounted for nearly three-quarters of the total increase in measles cases in 2018.
The World Health Organization has deemed vaccine hesitancy -- the reluctance or refusal to vaccinate despite the availability of vaccines -- as a top 10 threat to global health in 2019.
"I think we are at a tipping point," Offit said. "I think people need to realize that a choice not to get a vaccine is not a risk-free choice. It's a choice to take a greater risk, and unfortunately right now, we are experiencing that greater risk."