EXPERT REACTION: No vaccine and autism link - even in kids with risk factors for autism

The study by Hviid and colleagues followed all more than 650,000 children in Denmark, including 6517 children diagnosed with autism, after measles-mumps-rubella MMR) vaccine amassing one of the largest studies ever on the safety of that vaccine.

Yet again, and with more detail than the existing dozen or more studies, they have shown that MMR vaccine is not linked with autism.

As they explored special risk groups, they were also able to show after MMR vaccination there was no higher rate of autism in children who had risk factors for developing the condition (such as sibling with autism), or higher rates during specified time periods after vaccination.

Looking forward, continuing to evaluate the MMR-autism myth when it has already been thoroughly debunked, will come at the expense of not pursuing other important research to better understand and prevent autism.

Social media continues to be a platform to propagate this and other fake news about vaccines, creating concerns among parents. We strongly encourage parents and the public to seek advice from reliable sources and qualified health professionals, such as their GP or practice nurse to discuss the importance and safety of immunisation.

All studies since the fraudulent paper of Andrew Wakefield published in the Lancet in 1998 have failed to find a link between MMR vaccination and autism. The paper was subsequently withdrawn but the damage had been done. An increase in vaccine hesitancy and refusal since then has been associated with repeated outbreaks of measles in industrialised countries in recent years, including Australia, with cases doubling in Europe in the last year.

Since measles is potentially lethal and highly infectious the ideal scenario would be to eradicate it from the world altogether, as was achieved with smallpox through vaccination. However, measles eradication requires more than 95% of people need to be vaccinated which will be hard to achieve while the mythical link between MMR and autism persists.

Hviid and colleagues performed a comprehensive country-wide analysis of more than 600,000 Danish children and greater than 5 million-person years of follow up, finding no evidence of a link between MMR and autism. It is the largest study yet to address this question.

Furthermore, there was no link between MMR and autism even in those deemed at high risk of autism. Perhaps it is time to finally lay to rest the false information that MMR causes autism and get on with the important goal of eradicating this deadly disease once and for all.

This important epidemiological study, undertaken using population-based registry data on over 650,000 Danish children born from 1999 to 2010, evaluated whether the MMR vaccine was associated with any increased likelihood of autism diagnosis.

Moreover, to address concerns raised about previous research in this area, the authors also investigated whether subgroups of children, who already had an increased likelihood of developing autism because of the presence of certain risk factors, might be particularly susceptible to the vaccine.

This was done by developing an autism risk score using relevant variables such as the presence of another sibling with autism, being born preterm or being born to older parents. Using several different modelling strategies as well as sensitivity analyses, no evidence of increased risk of autism diagnosis after MMR was identified.

The paper reinforces the important public health message of maintaining high community vaccine coverage particularly in light of the lack of any association of MMR with childhood autism.

Over 20 years have passed since the publication of a controversial Lancet paper that turned a number of parents around the world against the measles, mumps and rubella (MMR) vaccine due to an implied link with autism.

The paper which included only 12 children was subsequently retracted in 2010 due to several elements of the study being incorrect.

Despite extensive research highlighting no risk for autism after MMR vaccination, and the World Health Organisation (WHO) and the Centre of Disease Control (CDC) being united in the assertion that there is no evidence of an association between the MMR vaccine and autism, vaccine acceptance continues to be an area of significant concern.

A recent study conducted by the Statens Serum Institut in Denmark has been published this week in the Annals of Internal Medicine.

This large scale 10-year cohort study of 657, 461 children adds to the surplus of research showing no increased risk for autism after MMR vaccination.

Although it is fantastic to see another high-quality study refute the myth of an autism and MMR vaccine link, 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

This high quality Danish study is very reassuring for anyone concerned about a possible link between MMR vaccine and autism.  This was a large study that followed all children born in Denmark to Danish-born mothers between 1999 through 2010 (657,461 children) and used a population registry to identify any subsequently diagnosed with autism. Comparing MMR-vaccinated with MMR-unvaccinated children it found no increased risk of autism in the vaccinated group. 

These results should help to reassure parents that MMR vaccine is extremely safe to use.  This is yet another piece of evidence to counter the sad legacy of the Wakefield study published more than 20 years ago in 1998. It raised a potential link between MMR vaccine and autism but has now been discredited and withdrawn by the journal that published it. The misplaced concern it created lowered MMR vaccine use, resulting in measles increases in several countries. This kind of ‘vaccine hesitancy’ has been identified by the World Health Organisation as a major threat to global public health.

It is important that parents vaccine their children with MMR to protect them from measles, mumps and rubella.  High vaccine coverage also stops these viral diseases from circulating, which is particularly important for measles because it is so infectious.

New Zealand achieved measles elimination in 2017 meaning that our vaccine coverage was sufficiently high to prevent sustained measles circulation. We are among a growing number of countries that have attained this status, contributing to the ultimate goal of global measles eradication. Although NZ continues to see cases of measles, including an increase in the first two months of this year, these cases are all linked to imported cases in travellers. 

It is important that New Zealanders travelling overseas check their MMR status, particularly teenagers and young adults who may not have received the recommended two doses of MMR vaccine.  Such vaccination will protect them and also reduce their chance of bringing measles back into New Zealand when they return.

The now long since retracted article that proposed that the MMR vaccine caused autism based on the purported claims of 8 parents has continued to generate scares more than 20-years later. Since that time high-quality research from multiple quarters quickly confirmed there was absolutely no association between the vaccine and autism, the nails went in the coffin one after another in fairly quick succession with a 2014 meta-analysis (that pools together several studies into an even bigger study) concluding no association. Five of those studies included involved 1,256,407 children. More recent studies continue to reinforce the safety of the vaccine.

"We know through modern technologies such as brain imaging and genomics that autism begins long before birth. It is well established that autism has a complex genetic component with many genes implicated in playing a role. Autism is more likely in siblings. Whether or not this predisposed a subgroup of kids to autism after MMR vaccine was first investigated in the US and the findings published in 2015. In that study 95,727 children who had older siblings were assessed for vaccine status and a diagnosis of autistic spectrum disorder. The study concluded three things. One, that receipt of the MMR vaccine was not associated with an increased risk of ASD and two, this was regardless of whether or not a sibling had autism. In other words there was no association, even among kids at higher risk. The third conclusion is that parents with an autistic kid were less likely to vaccinated subsequent children – leaving them more susceptible to disease.

"This most recent study goes even further and includes over half a million children. The message is loud and clear. There is no difference in the risk of autism between vaccinated and unvaccinated kids – even for kids with a higher risk for developing autism.

"I think this reasonably puts to bed the notion that MMR might trigger autism in susceptible subgroups of children. The coffin is both nailed and superglued shut then hermetically sealed.

In general, I believe that parents want to do what is best for their children. However, as a paediatric neuropsychology researcher and clinician, and parent and grandparent, I find it essential that we rely on findings of well-designed research such as the article due to appear in the Annals of Internal Medicine about the lack of a vaccine-autism link.

In a sample of over 500,000 children followed for several years, using data available through the health system, MMR vaccination did not increase the risk for autism, or trigger autism even in those susceptible due to other factors such as family history. The carefully analysed results add to an already long list of studies that debunked faulty ideas about vaccinations.

This study is another reminder that we need to guard against biases informed by erroneous information when making important decisions about the causes and management of childhood disorders. To ignore these findings would be irresponsible in my opinion and may put children at increased risk as believing dangerous myths instead leads to poor healthcare choices.

Sadly, there will still be those who cling to conspiracy theories or coincidental evidence that confirms their fears or suspicions.

The scientific method is not always applied perfectly and not all findings tell the whole story but it is the best tool we have for testing our guesses about how things work.

Helping parents and the general public become informed consumers of research findings as they advocate for children is a key role for academics and clinicians across all healthcare disciplines.

This comprehensive study across an entire population of over half a million children born in Denmark over 10 years definitively confirms the findings of previous studies that there is no association between administration of the MMR vaccine and subsequent development of autism, or of any of the components of the autism disorder spectrum , even in children recognised as at increased familial risk. It should further reassure parents and prospective parents that MMR vaccination is safe.