A new study published Monday looked into the question of whether the measles-mumps-rubella (MMR) vaccine is connected to a greater risk of autism.
As in previous research on the topic, the researchers found no link.
This study, published in the journal Annals of Internal Medicine, examined nearly every child born in Denmark between 1999 and 2010 – a total of 657,461 people. Researchers broke the children into groups based on their risk of being diagnosed with autism: children with a sibling who has autism are at higher risk of being diagnosed themselves, for example.
Even in the higher-risk groups, there was no association between the MMR vaccine and an autism diagnosis.
“We found no support for any association between MMR vaccination and autism,” said Dr. Anders Hviid, of the Statens Serum Institut and co-author of the Danish study. “No support for an association in susceptible children (children with autism risk factors such as having siblings with autism or having older parents). No support for a regressive phenotype clustering in the period after vaccination. No support for an association when comparing MMR vaccinated children to children completely unvaccinated.”
This same team of researchers published a similar study in 2002, following controversies surrounding a paper by the now-discredited Andrew Wakefield in the Lancet, which claimed to have found a link between the MMR vaccine and autism. The Lancet has since retracted the article, saying that several elements of the paper were “incorrect.”
“Today, this putative association still causes concern among parents and challenges vaccine uptake,” Hviid said. “We felt that a re-examination in the same setting as our original study would be a valuable and timely contribution. In our new study, we have more children, more autism cases, and longer follow-up.”
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“It’s really a comprehensive look at essentially the entire population of children in Denmark,” said Dr. Karina Top, a pediatric infectious disease specialist and investigator at the Canadian Centre for Vaccinology.
“This just lends further weight to the agreement in the scientific community and public health and health officials that MMR does not cause autism.”
And there is a lot of agreement: a 2014 meta-analysis on the question identified five cohort studies and five case-control studies since 1998, none of which found evidence of an association between vaccines and autism.
Hviid said he welcomes any well-conducted study on the issue as it will only strengthen the evidence. “However, from a scientific standpoint, the question has been as thoroughly answered as is possible.”’
Top said she hopes this research reassures parents that the MMR vaccine is safe and shows that vaccine safety is a priority for the scientific community. “Parents can be reassured that we work very hard to make sure vaccines are safe.”
But, she said, “I think we have enough data, enough studies, enough high-quality studies to say that we don’t need to keep looking at this question.”