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Home » MMR vaccine and autism – once again, there is no association

MMR vaccine and autism – once again, there is no association

Despite the lies of the anti-vaccine religion, a huge recent Danish study has, once again, debunked any link between the MMR vaccine and autism. This is like the 140th peer-reviewed study that says the same thing – vaccines do not cause autism.

This study is particularly robust and conclusive, and it adds to the settled science that the MMR vaccine and autism are unrelated. And it is further evidence that the fraud perpetrated by Mr. Andrew Wakefield did nothing more than cause children to be put at risk of measles. 

But will this cause the anti-vaxxers to shut up? Of course not, because they prefer pseudoscience to real science.

All about measles

Measles, also known as rubeola (and not to be confused with rubella) is an infectious disease caused by the measles virus. It is extremely contagious, easily passing from one individual to another.

Despite the claims of the anti-vaxxers and anecdotes from adults, the disease is dangerous. According to the CDC, the complications from measles can be mild, such as diarrhea. However, more serious complications include:

  • Pneumonia that requires hospitalization
  • Acute brain inflammation
  • Subacute sclerosing panencephalitis (SSPE), a progressive brain inflammation that requires a lifetime of medications for treatment if caught early enough. About 1 in 609 children less than 12 months old who contract measles develop SSPE. There are numerous tragic stories of children who contracted SSPE after the measles.
  • About 1 in 1000 will develop acute encephalitis which leads to permanent brain damage.
  • About 1-2 out every 1000 children who contract measles will die.

Furthermore, measles can suppress the immune systems for months, and this can contribute to chronic bacterial infections like otitis media and bacterial pneumonia.

Measles is not a trivial disease – it can cause serious long-term neurological damage and death. And it all can be prevented with a simple vaccine.

And the MMR vaccine, for measles, mumps, and rubella, prevents all of these complications because it is over 97% effective in preventing this dangerous disease. 

mmr vaccine and autism
This is Copenhagen, Denmark. They do good science here. Photo by Nick Karvounis on Unsplash.

New MMR vaccine and autism study

The cohort study, by Dr. Anders Hviid et al., was published in the Annals of Internal Medicine, a top peer-reviewed journal. The researchers examined 657,461 children born in Denmark from 1999 through 31 December 2010, with follow-up from 1 year of age and through 31 August 2013. Of that group, 6,517 children were diagnosed with an autism spectrum disorder, an incidence rate of 129.7 per 100,000 person-years (see Note 1).

For this study, Hviid et al gathered data from the Danish Civil Registration System from 1999 to 2010, which contained information on MMR vaccine status, receipt of other childhood vaccines, diagnosis of autism, sibling diagnosis of autism, as well as other risk factors for autism such as smoking during pregnancy, parental age, and 5-minute Apgar score.

Originally, the voluntary Danish childhood vaccination program recommended the first dose of the MMR vaccine at age 15 months, with a second dose at age 12 years. However, beginning in 2008, the second dose was recommended to be given at age 4 years, with boosters given in later childhood. This is slightly different than the CDC-recommended schedule of the first dose at 12-18 months with the second dose at 4-6 years. 

The key results were:

  • The risk for an autism diagnosis was slightly lower in vaccinated than in unvaccinated children, a fully adjusted hazard ratio (aHR) of 0.93. This represents about a 7% lower risk of autism in vaccinated children. I could stop right here because that is convincing and credible evidence that the MMR vaccine and autism are unrelated, except that there is a smaller risk for children who receive the vaccine.
  • Moreover, receipt of the MMR vaccine was shown to have a reduced risk of autism for girls compared to boys (aHR 0.79). This probably doesn’t mean that the MMR vaccine is better for girls than boys, it’s more that there is a higher risk of autism in boys, irrespective of vaccine status, than for girls.
  • There was some variability for risk of autism in different birth cohorts.
  • The MMR vaccine also was not related to an increased risk of developing autism for kids who had autistic siblings, who received other vaccines in early childhood, or were considered to be at high-risk for autism. 

These results show that the risk of autism is either the same or slightly lower for vaccinated as opposed to unvaccinated children. Except for girls, where the risk for autism was substantially lower in vaccinated compared to unvaccinated girls. 

Unrelated to MMR vaccination status, the researchers looked at other variables that were interesting for autism research:

  • Male sex: aHR 4.02.
  • Born in a late birth cohort (2008-2010): aHR 1.34. This is puzzling, but it could be related to better diagnoses.
  • No early childhood vaccinations: aHR 1.17. That means that there is a 17% increased risk of autism in children who are not vaccinated. This alone demolishes the myths about vaccines and autism.
  • Siblings with autism at study entry: HR 7.32 (95% CI 5.29-10.12).

This study shows similar results as found in another nonoverlapping cohort study of over 570 thousand Danish children published in 2002. The main results were similar between these two studies, which supports the internal and external statistical validity of both.

In an accompanying editorial, Saad B. Omer, MBBS, MD, Ph.D., of Emory University’s Rollins School of Public Health, and Inci Yildirim, MD, Ph.D., MSc, of Emory School of Medicine in Atlanta, concluded that:

Even in the face of substantial and increasing evidence against an MMR–autism association, the discussion around the potential link has contributed to vaccine hesitancy. As a result of a successful immunization program, measles was declared eliminated in the United States in 2000. However, misinformation and the reluctance of many parents to vaccinate their children contributed to the 2015 measles outbreak in Disneyland in California and the 2017 outbreak in Minnesota. Five outbreaks have already been reported only in 2019, in which the majority of cases were unvaccinated.

Therefore, generating evidence on MMR vaccine safety may be useful but is certainly not sufficient. It has been said that we now live in a “fact-resistant” world where data have limited persuasive value. So how do physicians and public health officials debunk the MMR–autism myth?

Well, I’ve been around the block a few times debunking anti-vaccine myths, and I know that anti-vaxxers will continue to use junk science, anecdotes, and outright lies to claim that the MMR vaccine and autism are linked, irrespective of high-quality scientific evidence like this. The best any of us can do is provide evidence that debunks this myth.

But let’s be clear. This study, and many others, continue to refute the retracted 1998 study from Wakefield which tried to claim that there was an MMR vaccine and autism link. 

mmr vaccine and autism
Another lovely picture of Copenhangen, Denmark. I spent a lot of time there, and it’s really wonderful. Photo by Orlova Maria on Unsplash.

Anti-vaccine ignorance responds

To be honest, I rarely read anti-vaccine trolling, whether in comments or in articles, because I cannot stand ignorance and science denial. It makes me sad since I have given my whole life to the study of science. 

But I was curious as to what the anti-vaccine terrorists, so I went to see what the Age of Lying about Autism reported about this article. Of course, it was bovine feces, because they wouldn’t know science even if you spotted them all seven letters. 

First of all, they whined that this study was sponsored by Norvo Nordisk, a Danish pharmaceutical company. Denmark is a small country, and the fact that Norvo Nordisk gave money for scientific research is irrelevant. Of course, they are not in the business of vaccines – Norvo Nordisk is one of the world’s largest manufacturers of human insulin. Now if this were an article about one of their insulin products, I might be worried.

Furthermore, Norvo Nordisk, as is typical for almost all sponsored research these days, has no control over the study design, analysis, or publication. None. But the anti-vaxxers love to use the Big Pharma shill gambit for only one reason – they have no evidence supporting their lies, so they invent a conspiracy. In other words, the anti-vaxxers use lies to support their fake science, so they assume that highly educated, highly ethical, and highly dedicated scientists do the same. 

Then, the Age of Lying about Autism uses the case of Poul Thorsen, a Danish former CDC researcher who embezzled money, as an indictment against all Danes. That’s like accusing all Americans of being serial killers because Ted Bundy was both American and a serial killer. Moreover, Thorsen was a thief, stealing over $2 million from a Danish university, but his research seemed to be impeccable.

James Lyons-Weiler, who writes anti-vaccine articles published in predatory journals, went on a hysterical rant about the article that made little sense. I’m not interested in his particular brand of scientific ignorance, but I’ll hit a few points:

  1. Because he has zero education, experience, knowledge or insight into epidemiology he tries to discredit the study by claiming that the “known” autism rate in Denmark is 1.65% while this study shows about 0.95%. He is comparing two different cohorts with different inclusion criteria – that’s like a fundamental error in epidemiology. Moreover, the results for Hviid et al. are internally consistent – they are comparing cohorts, vaccinated and unvaccinated, that shows a lower autism rate in vaccinated children.
  2. He laughably wants to use anecdotes in his comment section to claim that vaccines lead to autism. In this light, please comment below if you ate a piece of chocolate and didn’t get a broken leg. I’d like to know.
  3. He thinks a major error in the study is that the study excluded immigrant children. Without getting into all the ins and outs of designing cohort studies, reducing variables is important. Because Denmark has a very thorough medical records system, it’s easy to check for everything from age of mother to vaccination date to autism diagnosis to everything. Immigrants may come into the system later, so there are lots of uncontrolled variables. But Lyons-Weiler, with zero evidence, wants us to believe that these immigrants have some other risk of autism. 

So the anti-vaxxers have nothing. 


Otherwise, I have seen zero serious and rational discussions from anti-vaxxers that would lead me to believe that there are any serious faults in this research. This study was huge, a requirement for a high-quality epidemiological study. The study examined almost every confounder we could imagine. The statistical analysis was impeccable. The conclusions were supported by the data.

But once again, the anti-vaxxers just have no evidence in support of their fear, uncertainty, and doubt about vaccines. They want to believe that the MMR vaccine and autism are related.

Of course, we have overwhelming evidence, not just from this Danish study, but from 140 more, that show no link between the MMR vaccine and autism. NONE. The lack of a link between vaccines and autism is settled science.

I wish we could move on from this pseudoscience pushed by the anti-vaxxers. But how many of you believe that?


  1. A person-year rate is generally calculated from a long-term cohort follow-up study (such as reported by Hviid et al.), wherein enrollees are followed over time and the occurrence of new cases of disease is documented. Moreover, the expected rate of autism spectrum disorder probably remains unchanged over the follow-up time of this study. This type of incidence rate is not used with cancer, for example, because the expected rate changes over time, usually with increased risks of many cancers as a person ages.


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