A massive study tracking almost every child born in Denmark over a decade has found no evidence that the measles-mumps-rubella vaccine (MMR) is in any way relevant to autism.
A link between the developmental condition and the vaccine was first raised in 1998 in a paper written by UK gastroenterologist Andrew Wakefield and colleagues, published in the medical journal The Lancet. The study involved just 12 children. It was eventually retracted. Wakefield was deregistered by Britain’s General Medical Council.
However, the study and its lead author remained in circulation for a dozen years before the action was taken, by which time the damage was done. Abetted by Wakefield, who positioned himself as an anti-vaccination activist, the MMR-autism story took on a terrible life of its own.
“Despite the small sample size, the uncontrolled design, and the speculative nature of the conclusions, the paper received wide publicity, and MMR vaccination rates began to drop because parents were concerned about the risk of autism after vaccination,” wrote researchers TS Sathyanarayana and Chittaranjan Andrade from India’s National Institute of Mental Health and Neurosciences in 2012.
Despite scores of subsequent studies showing no relationship between MMR (or any other vaccine) and autism, the anti-vax movement continues to grow in influence – with lethal effect.
Earlier this year the World Health Organisation (WHO) listed “vaccine hesitancy” as one of the top 10 global health threats of 2019. The designation followed the alarming revelation that in 2018 measles cases worldwide soared almost 50% on the previous year – killing 136,000 people.
In Ukraine, one of the worst-hit countries, measles cases in 2018 jumped from roughly 5000 in 2017 to 35,000 the following year. Case reports in the US bounced by 559%.
“Measles may be the disease, but all too often the real infection is misinformation, mistrust and complacency,” UNICEF executive director Henrietta Fore said last month.
Given the self-sustaining nature of modern conspiracy theories it might be too much to expect that the latest research will convince anti-vax activists that their fears are misplaced, but, at the least, the results provide solid grounds for rebuttal.
Researchers led by Anders Hviid from the Statens Serum Institut in Copenhagen used Danish population registries to study almost all children born in the country between 1999 and 2010 – a total of 657,461.
The children were tracked from birth until the study period ended. Denmark has an excellent health data-gathering system, and Hviid and colleagues were able to collate not only vaccination status – for MMR and other conditions – but also autism diagnoses and potential complicating factors such other illness or parental socio-economic disadvantage.
The researchers looked at five internationally accepted descriptions relating to autism: autistic disorder, atypical autism, Asperger syndrome, other pervasive developmental disorders, and unspecified pervasive developmental disorders. They also took into account genetic risk factors – such as parents or siblings with the condition – and epidemiological data, such as geographic or temporal clustering of autism cases.
Doing so, they write in a paper published in the journal Annals of Internal Medicine, was essential. In a previous study in 2002, Hviid and others looked at a nationwide cohort of 573,300 children, found 738 cases of autism spectrum disorders, and concluded that there was no link between the development of the condition and the MMR vaccination.
Not all vax sceptics, it turned out, were convinced by the evidence.
“A criticism of our and other previous observational studies has been that these have not addressed the concern that MMR vaccination could trigger autism in specific groups of presumably susceptible children, in contrast to all children,” the authors write.
“The current study addresses this concern in detail. We evaluate the risk for autism after MMR vaccination in subgroups of children defined according to environmental and familial autism risk factors.
“Another criticism has been that MMR is associated with a regressive form of autism, leading to a clustering of cases with onset shortly after MMR vaccination. We evaluate the risk for autism after MMR vaccination in specific periods in detail.”
And the findings this time? Bupkis. The chances of developing autism is exactly the same, whether or not children are vaccinated.
“The study strongly supports that MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination,” the authors conclude.
In an editorial in the same issue of the journal, doctors Saad B Omer and Inci Yildirim, both of Emory University in Georgia, US, praise the results of the new study, but lament its existence.
There is overwhelming evidence, they note, that the MMR vaccine is not in any way related to autism development.
“In an ideal world, vaccine safety research would be conducted only to evaluate scientifically grounded hypotheses, not in response to the conspiracy du jour,” they write.
They acknowledge that in the current vaccine-hesitant times, new studies are useful because they add to the weight of evidence, but note also that conducting them ties up people and resources that might otherwise be deployed in new and valuable research.
Omer and Yilirim, however, do not think the latest research – or any similar studies still to come – will turn the tide.
“Generating evidence on MMR vaccine safety may be useful but is certainly not sufficient,” they state. “It has been said that we now live in a ‘fact-resistant’ world where data have limited persuasive value.”
Andrew Masterson is a former editor of Cosmos.
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