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Autism and the MMR Vaccine:

An epidemic of misinformation.

By Kristina Hamner-Yonke

October 5, 2009


In this paper I will address the proposed link between the MMR vaccine and Autism. My analysis will include both an examination of popular knowledge on this topic from the Internet and an examination of the findings in scientific literature. In addition I will investigate possible causes for the discrepancy in information on the MMR vaccine and autism found on the Internet versus in scientific journals and how this discrepancy threatens public health.  

What is Autism? 

Autism is a disorder of neural development and is one of the five pervasive developmental disorders (PDDs). Its symptoms include impaired social interactions, problems communicating, and restricted, repetitive, and stereotyped behaviors. (NIH-autism)

Autism is a spectrum disorder so the symptom severity can vary widely. Also it has been found to have a large genetic component; in monozygotic twins there is a 90% chance of one twin being affected if their sibling has the disorder. In addition the disorder’s prevalence is about 6 per 1,000 people and is four times more common in males for unknown reasons. The number of people diagnosed with autism has increased steadily since the 1980s. Symptoms usually appear between the ages of one and three. When the child turns two years old and fails to develop language skills the diagnosis is usually confirmed. Some symptoms include limited eye contact, difficulties in speech production, and less attention to social stimuli. Children with autism tend to have less secure attachment to their primary caregivers due to these social impairments. In addition about 20% of autistic children go through “regression” where previous social and language skills of normal development are lost. Unfortunately there is currently no cure for autism however some treatments include behavioral therapy and modified diet. 

What is vaccination?

Vaccination is the process by which non-harmful versions of pathogens are introduced to a person’s immune system. When the pathogen enters the body B cells of the immune system identify the pathogen as “non-self” and create antibodies that tag the intruding antigen for destruction by other immune cells. In addition memory B cells are created and lay dormant. In this way the body is now prepared to mount a quick and effective immune response in case it is exposed to the pathogen again through the environment.



What is the MMR vaccine?

The MMR vaccine protects against measles, mumps, and rubella (german measles). The vaccine includes a mixture of these three viruses in non-harmful forms and before 2001 it included the mercury-based preservative thimerosal. It is generally required for school entry. The shot comes in two doses with the first one being administered at the age of 12-15 months and the second dose around 4 or 5 years old. The second shot is to ensure measles immunity in the 5-10% who do not become immune after the first dose. The symptoms of mumps are fever, headache and swollen glands and can lead to deafness, meningitis, swollen testicles or ovaries, and death. Rubella or German measles can cause serious birth defects in the fetus if the mother is infected during pregnancy. Lastly the symptoms of measles include cough, runny nose, rash, eye irritation and can lead to pneumonia, seizures, brain damage and death.(NIH-MMR vaccine)


The measles virus in particular is very important to immunize against because it is highly contagious through the air. Before the discovery of the vaccine measles was an epidemic in the United States with three to four million cases per year and 450 deaths per year. It was an expected part of life like catching a cold however after the vaccine became available in 1971 the cases dropped by 99 percent.(measles)


Why do people think the MMR vaccine causes autism? 

 In 1998 Dr. Andrew Wakefield a doctor in experimental gastroenterology at London’s Royal Free Hospital published a study in which he hypothesized that the MMR vaccine may cause autism. According to Wakefield after inoculation with the MMR vaccine the measles virus infects the bowels of certain children and this leads to a leaky gut that allows the passage of opiate-like peptides into the blood. Once they reach the brain CNS development is stalled due to the peptides’ depressive effect. This study caused a panic in many parents and caused many of them to forgo vaccinating their children leading to an increased risk for epidemic in the entire population.

In addition there is a temporal correlation between the age of onset of autism and the time that children usually receive the first dose of the MMR vaccine. Both the onset of autism and the first dose of the MMR vaccine occur between 18 to 24 months. However the temporal correlation does not mean that there is a causal relationship between the two. Dr. Paul Offit, chief of infectious diseases at the Children's Hospital of Philadelphia, Pennsylvania, explains the correlation: "So statistically, it will have to happen where some children will get a vaccine. They will have been fine. They will get the vaccine, and they will not be fine anymore. And I think parents can reasonably ask the question, 'Is it the vaccine that did this?'"(CNN)


Lastly there has been a recent rise in the incidence of autism that seemingly coincides with the use of the MMR vaccine. Parents are worried that there is an autism epidemic however the real reason for the increase is a broadening of diagnostic criteria. This change was triggered by the US Department of Education classification of Autism as a childhood disorder meriting special education services in 1991. As a result more effort has been put into recognizing an diagnosing autism and autism spectrum disorder.


Online Information 

When one searches the key words “autism” and “MMR” on the Internet three types of websites provide information on these subjects: government health websites, news websites, and blogs.  

      A:  Government Health Websites

There are multiple health websites that address the proposed link between the MMR vaccine and autism. For example the National Institutes of Health website provides six autism-related fact sheets including one titled “Autism and the MMR Vaccine” which explains all of the scientific findings on the supposed link and also gives information on current research efforts that are directed toward this question. (NIH)

In addition the Centers for Disease Control and Prevention website has a page that explains the benefits and safety risks of the MMR vaccine in its “Vaccine Safety”  section. The web page explains that the vaccine protects against dangerous infectious viruses and cites and provides links to many scientific studies that found no connection between autism and the vaccine. (CDC-vaccine safety)

These government websites aim to get the correct information out to the general public so that they can make informed decisions about their health. The health websites cite scientific findings as support for their health suggestions and therefore deal objectively with the information. These websites give the reader a clear-cut answer regarding the question of a possible link between the MMR vaccine and autism. The answer, as supported by scientific studies, is that there is no causal link.

      B: News Websites 

The articles on the news websites aim to report on the current difference of opinion between parents of autistic children who blame the disorder on the MMR vaccine and scientists who have found no evidence of this supposed link. A good example is the CNN online article, “Vaccine-Autism question divides parents, scientists.” by David S. Martin. In this article Martin includes an interview with the parents of Michelle Cedillo who developed the symptoms of autism soon after her MMR vaccine. The Cedillos are now suing the government through the National Vaccine Injury Compensation Program because they believe the vaccine caused their daughter’s autism. In addition to reporting on the parents’ claim that there is a connection Martin included the official position of the Center for Disease Control and Prevention that there is no causal link. News articles like the one above are informative on both sides of the situation and exemplify objective reporting.  Other news articles (in print and online) disseminate scientific findings to the general public.

In 1998 the news media played a large role in creating the hype around Dr. Wakefield’s hypothesis that the MMR vaccine was related to autism because it was the “hot” story at the time. However, in recent years most of the scientific studies have found that the vaccine does not cause autism and the news media has dutifully reported on these findings. In fact one article posted on Times online from the Sunday Times documented journalist Brian Deer’s investigation of Dr. Wakefield’s 1998 study. In the article Deer explains how, along with the General Medical Council (GMC), he uncovered evidence that Wakefield altered data in the study, “In most of the 12 cases, the children’s ailments as described in The Lancet were different from their hospital and GP records.” (Brian Deer). He also found that before starting the study Wakefield was involved in patenting an alternative to the MMR vaccine. Ten days after the publication of this investigation ten of the thirteen co-authors retracted their association with the study.  

   B. Blog Websites

The last type of website that provides information about the purported link between autism and the MMR vaccine is the blog. Autism blogs are mostly created by and written on by the parents of children with the disorder. The online community of a blog gives the parents a place to talk about their feelings and observations on having a child with autism.  Due to the fact that there are no known causes (except for genetic factors) and no cure the parents take a proactive approach on these blogs and exchange information about possible treatments.  A common theme in these blogs is the belief that the MMR vaccine is the cause of their child’s autism. 

For example the Age of Autism blog has a post entitled “MMR and the simple truth about Autism”  by Dan Olmsted. In this post he explains his view that the vaccine causes autism, “Lest the CDC miss the point again, let's repeat it: Yes, the MMR causes autism.

( He cites a doctor reporting ten cases of autism in children who received the MMR vaccine as his evidence. Mr. Olmsted also expresses that he believes the pharmaceutical company Merck (who manufactures the MMR vaccine) and the CDC are distorting scientific findings in order to salvage the current vaccination program and its profits. He presents no proof of this conspiracy and also only provides anecdotal evidence from a doctor and not a controlled scientific study as his proof of a link between MMR and autism. An example of a typical comment on this blog is one by Nancy who writes, “My daughter is now 24 years old. She has Aspergers (sic) (an autism spectrum disorder). The day after her MMR, she "came down" with strep throught (sic),vomiting, all of a sudden she was not able to tolorate (sic) her formula, got a foggy look in her eyes. Was not acting her normal way”. As shown by this comment this blog is a place for parents of autistic children to commiserate. It is also a place to post anecdotal evidence of a connection between the vaccine and autism but this is not a good source of information on the topic because it is too subjective and not held up to the rigorous standards of scientific research. 

Another blog is titled “Autism & vaccination-parents” and includes a page of quotes from parents who claim that the MMR vaccine caused their child’s disorder. Some examples include  "Our son developed normally meeting all major milestones but inexplicably regressed beginning at the age of 15 months following his MMR vaccination”, and "Liam was a normally developing baby until June 27, 1997, when he received his MMR and Hib vaccines.” (

 In this blog parents describe the temporal correlation between the onset of their child’s autism symptoms and the date of their first MMR vaccination. Due to this correlation they believe that the vaccine caused the disorder however there is no way to infer causation from correlation unless statistical analyses of research data are used. These bloggers are using anecdotal evidence to try to prove a causal relationship however this reasoning is faulty and is not objective.  

Lastly celebrities such as Jenny McCarthy and Jim Carey have blogged about their son’s autism and how they think it is related to vaccinations. For example on the blog “Babyrazzi: celebrity baby news” McCarthy wrote, “We think our health authorities don’t want to open this can of worms, so they don’t even look or listen. While there is strong debate on this topic, many parents of recovered children will tell you they didn’t treat their child for autism; they treated them for vaccine injury.” ( Jenny McCarthy is a celebrity and for this reason parents of autistic children look to her as a role model. Also, due to this celebrity she is able to transmit her opinion on the debate to many more people; for example she wrote a book called Louder than Words about her son’s battle with the disorder.  This book and her blogs are much more accessible to the general public than scientific journals however parents must realize that her advice is anecdotal and not as dependable as the results of an experiment.

Scientific Evidence:

Illeal lymphoid nodular hyperplasia, non-specific colitis and regressive developmental disorder in children. Wakefield AJ, Murch S, Anthony A et al.  

This 1998 case report was the study that first suggested a causal link between the MMR vaccine and autism. The patients were twelve children who had a history of normal development that was followed by regression due to pervasive developmental disorder. The investigators performed gastroenterological, neurological, and developmental assessments of the children as well as a review of their developmental records. In addition, the investigators performed ileocolonoscopy and biopsy sampling, MRI, EEG and lumbar puncture on all of the patients. They performed these tests to assess the children’s gastrointestinal and developmental condition and to see if there is a pattern of colitis and ileal-lymphoid nodular hyperplasia in children with PDD. According to the study, “In eight children, the onset of behavioral problems had been linked, either by the parents or by the child’s physician, with measles, mumps and rubella vaccination.”(638). Apparently the developmental deterioration in these eight children occurred about six days after the vaccination however the onset of the gastrointestinal symptoms was not able to be assessed accurately because the children were not toilet trained. Wakefield postulated that the intestinal inflammation and PDD seen in the children might be due to the influence of the measles virus in the MMR vaccine. This is because they found gastrointestinal problems and the measles virus in bowel tissues of the eight children with autism spectrum disorders. Without going into the allegations of Sunday Time reporter Brian Deer this study has some striking flaws. The first is that the sample size of twelve patients is much to small to generalize the findings to the population at large. Secondly in order to infer that gastrointestinal problems contribute to autism they must precede the onset of the disorder however there is no mention of the chronological order of the MMR vaccine, the onset of GI issues, and the onset of autism symptoms. If the gastrointestinal symptoms occurred before the MMR vaccine there would be no relation.  

Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study. Mady Hornig, Thomas Briese, Timothy Buie et al. 

In 2002 Wakefield published a refined version of his 1998 study entitled, Measles, mumps, rubella vaccine: through a glass, darkly. In this study he postulated that measles virus RNA in the bowel tissue of subjects was from the MMR vaccine (although this RNA was never tested could have been wild measles virus). According to the study the mv RNA caused GI inflammation the increased the permeability of the gut allowing it to leak neuroactive chemicals (like peptides and casein that have an opiod effect on the brain) and in turn these leaked chemicals caused symptoms of autism.  

The 2008 Hornig case-control study replicated the Wakefield study to see if children with gastrointestinal (GI) problems and autism are more likely than children with GI problems alone to have inflammation and/or measles virus RNA in their bowel tissues. It also set out to determine if autism and GI problems are linked temporally to inoculation with the MMR vaccine.  The study population consisted of 25 cases with autism and GI issues and 13 controls with only GI issues. The age of MMR vaccination was similar for both cases and controls and all subjects were between 3-5 years old. Parents reported their children receiving the shot six months or more before the study. The investigators found no differences between the case and control group in the amount of measles virus RNA in the bowel biopsy. Only 20% of the subjects received the MMR vaccine before the onset of GI symptoms and also had the GI symptoms before the Autism symptoms resulting in a non significant finding (P = 0.03).  Therefore the study findings support the null hypothesis that there is no association of autism with the MMR vaccine or measles virus RNA in the GI tract. A possible issue with this study is its small sample size of 38 which is too small to generalize to the population at large.  

A Population-Based Study of Measles, Mumps, and Rubella Vaccination and Autism. Kreesten Meldgaard Madsen, Anders Hviid, Mogens Vestergaard, et al. 

This is a large retrospective cohort study conducted in Denmark that provides convincing epidemiological evidence that the MMR vaccine does not increase the risk of autism. The cohort studied totaled 537,303 children born in Denmark between January 1991 and December 1998. This data was obtained from the Danish Civil Registration System. Of the cohort, 440,655 (82%) received the MMR vaccination, 316 children had autistic disorder and 422 had autistic spectrum disorder. Using statistical analyses the researchers found the relative risk of developing autism in association with the MMR vaccine to be 0.92 (confidence interval 0.68-1.24). Because this relative risk factor is below 1 the MMR vaccine has either no effect or is a protective factor in relation to autism.

There were 100,000 children in the cohort who did not receive the MMR vaccine so the researchers found the risk of autism is similar in vaccinated and unvaccinated children. Also they found no temporal clustering of cases of autism at any time point after inoculation with the MMR vaccine. In conclusion this study provides strong arguments against a causal relation between the MMR vaccine and autism. This study’s strong points include its large sample size that allowed for small confidence intervals and large number of vaccinated and unvaccinated subjects that allowed the calculation of relative risk. One weakness is the fact that the research was done with data that had been previously recorded so the researchers could not be certain of its accuracy.   


In conclusion the hype of Wakefield’s 1998 study is still impacting the decisions of parents today on whether to vaccinate their children with MMR. This misinformation continues to be spread through blogs even though it has come to light that data was altered in Wakefield’s study and the CDC and NIH both state that there is no causal link between the vaccine and autism.  The majority of scientific literature has also found no evidence of a causal link between the two. Yet still parents refuse to vaccinate their children even though the viruses that the MMR vaccine protects against have been proven to cause disease.

A possible reason that parents have started to fear the MMR vaccine is because of the profound emotional context of the autism disorder. Autism has no known cause or cure although the most common theory holds that genetic factors interact with environmental triggers resulting in the disorder. The lack of information on how to treat or avoid this disorder leaves parents mistrustful of a scientific community that cannot give them answers. The parents may feel powerless over the situation and the idea that they can prevent autism by avoiding the MMR vaccine gives them some control.

The emotional context of the disorder goes deeper as it interferes with new emotional bonds between parent and child. A child with autism will be developing normally and then suddenly between 18-24 months they will begin to regress right in front of their parents’  eyes. Due to the impairment of social function the close relationship between parent and child will become more distant. The parents feel as if their once normal child is lost. I posit that due to the powerful emotions that surround this disorder parents are more apt to turn a blind eye to scientific evidence in favor of anecdotal evidence that can give them more hope.

In order to correct this situation I would suggest a campaign to give parents of young children the correct information on the subject. This includes increasing parent’s access to scientific literature (for example I can google Jenny McCarthy and read her views but I need to have special access to read the scientific articles on Web of Science). Also I would make sure that there is more information on the mechanisms and benefits of the MMR vaccine.

Works Cited

Kreesten Meldgaard Madsen, Anders Hviid, Mogens Vestergaard, et al. (2002). A Population-Based Study of Measles, Mumps, and Rubella Vaccination and Autism. New England Journal of Medicine, 347, 1477-1482.

Mady Hornig, Thomas Briese, Timothy Buie et al. (2008). Lack of Association between Measles Virus Vaccine and Autism with Enteropathy: A Case-Control Study. PLoS One, 9, 31-40.

Wakefield, A.J., Murch, S., Anthony, A. et al. (1998). Illeal lymphoid nodular hyperplasia, non-specific colitis and regressive developmental disorder in children. Lancet, 351, 611-612.



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