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What Evidence Is Used To Conclude That Vaccines Do Not Cause Autism?

The CDC website states that, "Vaccines do not cause autism."  What evidence do they use to make that claim?  It goes on further to state that, "Some people have had concerns that ASD might be linked to the vaccines children receive, but studies have shown that there is no link between receiving vaccines and developing ASD. The National Academy of Medicine, formerly known as Institute of Medicine, reviewed the safety of 8 vaccines to children and adults. The review found that with rare exceptions, these vaccines are very safe."

I have linked the report from the IOM below.  Using the search tool at the top of the report I did a search for the word "autism" which made it easy to find each instance autism is referenced in the report. Quickly I could see that the statement made by the CDC was deceptive and misleading.  Again, the statement made by the CDC is that the IOM reviewed the safety of 8 vaccines.  However, the IOM only looked at the evidence available for two vaccines in relationship to autism.  The committee reviewed 22 studies to evaluate the risk of autism after the administration of MMR vaccine. Twelve studies were not considered due to passive surveillance data used in the studies.  Six studies were not considered due to "very serious methodological limitations".  Based on the FOUR remaining studies IOM determined "The evidence favors rejection of a causal relationship between MMR vaccine and autism".  The IOM also looked at a possible relationship to DTaP vaccines and autism.  The committee reviewed ONE study to evaluate the risk and the study  "was not considered in the weight of epidemiologic evidence because it provided data from a passive surveillance system and lacked an unvaccinated comparison population."  The IOM concluded that, "The epidemiologic evidence is insufficient or absent to assess an association between diphtheria toxoid–, tetanus toxoid–, or acellular pertussis–containing vaccine and autism."  Further misleading the CDC stated that according to this review, "with rare exceptions, these vaccines are very safe".   When in fact the IOM reviewed available literature for 158 of the most common injuries thought to be related to vaccination, in which they found the science convincingly supports a causal relationship for 14 of these serious injuries, including pneumonia, meningitis, hepatitis, MIBE (deadly brain inflammation a year after vaccination), febrile seizures, and anaphylaxis. The review found sufficient evidence to support “acceptance of a causal relationship” for 4 additional serious injuries.  The IOM was unable to find sufficient evidence to conclude or deny the relationship of 135 other serious injuries.

The second reference used by CDC to support their claim that VACCINES DO NOT CAUSE AUTISM is a CDC study published in 2013 that focused on the number of antigens received during the first two years of life.  They concluded that, "increasing exposure to antibody-stimulating proteins and polysaccharides in vaccines during the first 2 years of life was not related to the risk of developing an ASD."  This study in no way evaluates whether VACCINES cause autism.  They don't look at how many vaccines each child received or which vaccines.  Antigens have never thought to have been the issue in regards to autism and vaccines.  Using this study on their website as proof that VACCINES do not cause autism is an insult to our intellegence.  It also shows the CDCs overall lack of concern about children and families who are impacted by autism.  If they wanted to prove that vaccines do not cause autism once and for all they would use the data they already have on millions of Americans and they would compare the rates of autism in the vaccinated against the rates in the un-vaccinated.  They refuse to do this study, and have gone a step further by moving these records into a private company making it impossible for anyone else to access these records.  Why? If they truly believe that VACCINES do not cause autism, why not do the study on vaccinated vs completely unvaccinated and end the debate once and for all???  I am not able to say the intentions of others but it certainly feels like they actually don't truly believe vaccines do not cause autism.  It seems as though they care more about protecting the vaccine program and pharma profits, than they do about 1 in 44 kids who are having their chance at a normal life stolen from them.

These are the only studies referenced on the CDC website in support of the claim that VACCINES DO NOT CAUSE AUTISM.  They only  reference TWO vaccines.  One of which, DTaP, the report could neither accept OR deny a relationship between the vaccine and autism.
But lets see what else they have to say.

The Stars

CDC goes on to state that, ​"vaccine ingredients do not cause autism".  Lets look at the research they have used to support that statement.



The first reference they use to support that claim is a 2004 scientific review by the IOM that concluded “the evidence favors rejection of a causal relationship between thimerosal–containing vaccines and autism.”  In the review the IOM describes the five studies used to make that conclusion. 


   1. Hviid et al., 2003; Association between thimerosal-containing vaccine and autism

  • Compared autism rates in those who received vaccines containing thimerosal with those that received thimerosal free vaccines.  ​

  • The mean age of diagnosis was 4.7 years old.  However, the study included cases and controls as young as 1 years old.  Meaning many of the subjects would later go on to receive an autism diagnosis.

  • Also, instead of counting "persons"  the authors counted "person-years of follow-up"  meaning each age group was considered equially despite the fact that younger age groups were much less likely to have been diagnosed with autism as those in older groups.

   2. Miller, 2004; Thimerosal exposure in infants and developmental disorders: a retrospective cohort study in the United kingdom does not support a causal association

  • A retrospective cohort study completed using records from a database in the United Kingdom, where autism prevalence rates were compared for children receiving Thimerosal-containing DTaP and DT vaccines.

  • Numerous statistical errors by correlating thimerosal exposure with year of birth.

  • The authors of this study never released the raw data so that a valid single-variable analysis could be conducted to ascertain the probability of an association between Thimerosal exposure and the risk of autism.

  • Also important is that the amount of thimerosal exposure in the UK was not comparable to that in the United States where children were getting larger exposures during younger periords of life.

   3. Verstraeten et al., 2003 Safety of thimerosal-containing vaccines: a two-phased study of computerized health maintenance organization databases

  • A cohert analysis of records from the Vaccine Safety Datalink done by the CDC.

  • This study had at least 5 phases.  Results from the first phase showed that infants who were exposed to greater than 25𝜇g of Hg in vaccines and immunoglobulins at the age of one month were 7.6 times more likely to have autism diagnosis than those not exposed to any vaccine-derived organic Hg.

  • The second phase they compared exposure from 3 months old instead of one month and found that children exposed to the maximum amount of organic Hg in infant vaccines (62.5𝜇g) were 2.48 times more likely to have autism diagnosis compared to those exposed to less than 37.5𝜇gof Hg in vaccines.

  • The third phase used different inclusion/exclusion criteria stratisfying the data the relative risk of autism for children at three months of Thimerosal exposure dropped to 1.69.

  • The fourth and fifth phase of the study used records from only two of the original HMOs and incorporated a third HMO, Harvard Pilgrim, into the analysis.  The HMO used different diagnostic codes and in this study they included children from 0-3 years old even though the average age of autism diagnosis was 4.4 years.

  • There was a lot of contraversy around the Verstraeten study.  Emails obtained through FOIA requests show that Verstraeten was receiving pressure from the CDC to use methods to deny a casual relationship between thimerosal and autism.

   4. Madsen et al., 2003; Thimerosal and the occurrence of autism: negative ecological evidence from Danish population-based data

  • CDC sponsored study that looked at whether discontinuing the use of thimerosal in vaccines in Denmark lead to a decreased rate of autism.  The study examined the data from 1971 to 2000 and reported that rate of autism increased with the removal of Thimerosal from vaccines starting in 1992.

  • However, autism rates only included those who were diagnosed in an inpatient setting from 1971-1994.  In 1995 the inclusion of those diagnosed in an outpatient setting were added.  The authors state that the outpatient setting had 4-6x that of the inpatient.  In a previous publication the same authors using the same data reported 93.1% of children were treated only as outpatients.  The inclusion of the outpatient population would explain why the numbers of autism cases continued to rise after phase out of thimerosal.

  • Also inflating the numbers was the inclusion of a large clinic in the dataset starting in 1993.  This clinic accounted for as many as 20% of autism patients nationwide.

  • Last, the diagnostic criteria for autism changed in 1994 resulting in an increased incidence by up to 25x what it was using previous diagnostic criteria.


  5.  Stehr-Green et al., 2003; Autism and thimerosal-containing vaccines: lack of consistent evidence for an association

  • Compared the prevalence/incidence of autism in California, Sweden, and Denmark with average exposures to thimerosal containing vaccines.

  • This study used the same data from Denmark as the previous study.  There was an artificial increase in autism rates by 20x following removal of thimerosal due to inclusion of outpatients starting in 1995, the inclusion of a large clinic accounting for 20% of cases in 1993, change in diagnostic criteria in 1994.

  • This study also used data from Sweden but looked at only inpatient cases of autism counting only a small portion of the actual cases of autism.

  • Also, children in Sweden received a maximum 75 micrograms of Hg by age two.  Children in California received up to 237.5 micrograms of Hg by 18 months.  

This same report by the Institute of Medicine also states that, "Absent biomarkers, well-defined risk factors, or large effect sizes, THE COMMITTEE CANNOT RULE OUT, based on the epidemiological evidence, the possibility that vaccines contribute to autism in some small subset or very unusual circumstances."

Your can veiw the IOM report HERE.

Read more about the flawed methods and manipulation of data-

Methodological Issues and Evidence of Malfeasance in Research Purporting to Show Thimerosal in Vaccines Is Safe

Study Misses Link Between Thimerosal and Neurodevelopmental Disorders

Letter to the Editor

M. GeierD. Geier; Published 2004; Medicine

Summarized conflict of interest issues, manipulated data, and suppression of initial findings in the Verstraeten study. 

"Since 2003, there have been nine CDC-funded or conducted studies that have found no link between thimerosal-containing vaccines and ASD. These studies also found no link between the measles, mumps, and rubella (MMR) vaccine and ASD in children." 


Thimerosal exposure in early life and neuropsychological outcomes 7-10 years late

Ֆ Barile JP, Kuperminc GP, Weintraub ES, Mink JW, Thompson WW

Conflicts & Issues- Overmatching phenomena meant that  cases and controls had very little difference in thimerosal exposure.


Prenatal and Infant Exposure to Thimerosal From Vaccines and Immunoglobulins and Risk of Autism

Price CS, Thompson WW, Goodson B, Weintraub ES, Croen LA, et al.

Conflicts & Issues: Overmatching phenomena meant that cases and controls had very little difference in thimerosal exposure. Prenatal thimerosal effect was hidden by cherry-picking data.


Neuropsychological Performance 10 Years After Immunization in Infancy With Thimerosal-Containing Vaccines

Tozzi AE, Bisiacchi P, Tarantino V, De Mei B, D’Elia L, et al.

Conflicts & Issues:  Study was completed using Italian vaccine schedule with much lower thimerosal exposure than U.S. schedule. No zero exposure control was use.


Thimerosal-containing vaccines: evidence versus public apprehension

DeStefano F. 

Destefano relied on flawed epidemiology studies from the U.K. and Denmark which  follow different vaccination schedules compared to the U.S. Data from California show clear correlation between thimerosal uptake and autism incidence.


Inactivated influenza vaccine (IIV) in children <2 years of age: Examination of selected adverse events reported to the Vaccine Adverse Event Reporting System (VAERS) after thimerosalfree or thimerosalcontaining vaccine

McMahon AW, Iskander JK, Haber P, Braun MM, Ball R. 

The definition of an adverse event was limited to site reactions and fever. No data were collected regarding any type of neurological outcome.


Early Thimerosal Exposure and Neuropsychological Outcomes at 7 to 10 Years

Thompson WW, Price C, Goodson B, Shay DK, Benson P, et al

Overmatching phenomena meant that cases and controls had very little difference in thimerosal exposure.


Safety of Thimerosalcontaining vaccines: a two-phased study of computerized health maintenance organization databases

Verstraeten T, Davis RL, DeStefano F, Lieu TA, Rhodes PH, et al

Effects were diluted through five separate iterations of the study. Numerous exclusion criteria were erroneously applied and data cherry-picking was done to dilute statistically significant effects.


Autism and thimerosalcontaining vaccines: lack of consistent evidence for an association

Stehr-Green P, Tull P, Stellfeld M, Mortenson PB, Simpson D.

Wrongfully dismissed autism rates in California as inclusion of milder ASD cases to obviate the rise in cases.


Autism and thimerosalcontaining vaccines: lack of consistent evidence for an association

Stehr-Green P, Tull P, Stellfeld M, Mortenson PB, Simpson D

There was an artificial increase in autism rates by 20x following removal of thimerosal due to inclusion of outpatients starting in 1995, the inclusion of a large clinic accounting for 20% of cases in 1993, change in diagnostic criteria in 1994.

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