An adjuvant is an ingredient used in some vaccines that helps create a stronger immune response in people receiving the vaccine. In other words, adjuvants help vaccines work better. Some vaccines that are made from weakened or killed germs contain naturally occurring adjuvants and help the body produce a strong protective immune response. However, most vaccines developed today include just small components of germs, such as their proteins, rather than the entire virus or bacteria. Adjuvants help the body to produce an immune response strong enough to protect the person from the disease he or she is being vaccinated against. Adjuvanted vaccines can cause more local reactions (such as redness, swelling, and pain at the injection site) and more systemic reactions (such as fever, chills and body aches) than non-adjuvanted vaccines.
By design then, vaccine adjuvants are necessarily toxic. This is because their purpose is to induce an immune response stronger than the immune response to the antigen component alone. The adjuvant is what makes the challenge to the immune system from the vaccine strong enough to induce immunological memory.
This is why the safety of vaccine adjuvants is so important to the safety of vaccines as a whole; the adjuvant is by design the most toxic part of the vaccine.
The CDC writes that:
Aluminum salts, such as aluminum hydroxide, aluminum phosphate, and aluminum potassium sulfate have been used safely in vaccines for more than 70 years. Aluminum salts were initially used in the 1930s, 1940s, and 1950s with diphtheria and tetanus vaccines after it was found they strengthened the body’s immune response to these vaccines.
Aluminum salts have indeed been used since the 1930s, as described in the earliest papers about aluminum adjuvants, such as Glenny 1926 and Volk 1942. Whether they have been used safely is the question at hand.
There were no safety studies done on the effects of Aluminum-Containing Vaccines (ACVs) prior to their routine use in infants. The only studies were of efficacy, tested by measuring antibodies. The first routine ACVs were the diphtheria, tetanus, and pertussis vaccines. These were later given as a combined vaccine, known as DTP, and then DTaP (the ‘a’ referring to acellular pertussis).
Up until 1990, the DTP vaccine was the only ACV given routinely to infants. After 1990 however, the number of ACVs on the recommended infant vaccine schedule started increasing. The Hib and Hepatitis B vaccines were added in 1991 and the Pneumococcal vaccine in 2000. They started being given in more doses and at a younger age. Infants today are considerably more exposed to aluminum from vaccines than infants of 30 years ago.
Aluminum and Neurodevelopmental Disorders
Aluminum is classified by the US Agency for Toxic Substances and Disease Registry (ATSDR) as a neurotoxin. This means the first harmful effects of aluminum overdose occur in the brain. The ATSDR describe aluminum as having “subtle neurological effects”, even at low doses. A steady increase in neurodevelopmental disorders, e.g. ASD, ADHD, and intellectual disability, is to be expected if aluminum adjuvants in infant vaccines are altering neurodevelopment.
We have seen an increase in neurodevelopmental disorders in line with increasing exposure to aluminum from vaccines. The increase cannot be explained away as expanded definitions, better diagnosis, or increased awareness. This ecological observation – the temporal correlation between ACV use and neurological disorders – calls for further research. As a neurotoxin, aluminum has to be a prime suspect in the search for causes of neurodevelopmental disorders.
The CDC writes that:
Newer adjuvants have been developed to target specific components of the body’s immune response, so that protection against disease is stronger and lasts longer.
None of the newer adjuvants are yet used in infant or childhood vaccines. They are thus of no relevance to an investigation of adjuvant safety in the infant and childhood vaccine schedule. The safety of adjuvants in this context means the safety of aluminum salts.
Safety Testing – Clinical Trials
The CDC writes that:
In all cases, vaccines containing adjuvants are tested for safety and effectiveness in clinical trials before they are licensed for use in the United States, and they are continuously monitored by CDC and FDA once they are approved.
In pre-approval clinical trials, potential new vaccines are tested against a placebo injection. The primary focus of the trials is efficacy; a vaccine is judged as successful when it results in the development of antibodies. Safety is a secondary consideration. Typically, immediate adverse reactions are recorded, there is active follow-up for only a week, and passive follow-up for only a year.
Pre-approval clinical trials will not pick up long-term adverse reactions, chronic conditions or altered neurodevelopment. No rare adverse events are picked up in the clinical trials, due to the small sample size.
For assessing adjuvant safety, pre-approval clinical trials are entirely useless. This is because both the vaccine being tested and the placebo contain adjuvant! The placebo is either a solution of adjuvant only, or an already-licensed vaccine. There are no safety tests of vaccine adjuvants in pre-approval clinical trials of ACVs.
Safety Testing – Monitoring
The post-approval monitoring systems of the CDC are the Vaccine Adverse Event Reporting System (VAERS) and the Vaccine Safety Datalink (VSD). VAERS is a system is for reporting immediate and short-term vaccine reactions. It cannot be used to monitor, for example, whether ACVs are causing autism. The VSD is a database that could easily and cheaply be used to conduct large-scale epidemiological studies. It is a data goldmine.
The Institute of Medicine, in their 2013 report “The Childhood Immunization Schedule and Safety: Stakeholder Concerns, Scientific Evidence, and Future Studies” recommended using the VSD to assess vaccine safety:
The most feasible approach to studying the safety of the childhood immunization schedule is through analyses of data obtained by VSD. VSD is a collaborative effort between CDC and 9 managed care organizations that maintain a large database of linked data for monitoring immunization safety and studying potential rare and serious adverse events. VSD member sites include data for more than 9 million children and adults receiving vaccinations on a variety of immunization schedules.
No studies have been on VSD data looking for a possible association between ACVs and neurodevelopmental conditions. The IOM’s call for more safety studies of the vaccine schedule has gone unheeded, so far.
The VSD has great potential to increase vaccine take-up by allaying many concerns people about vaccine safety. For reasons unknown, the CDC refuses to allow researchers to access the VSD data to perform these kinds of studies. Nor has it produced any studies of its own using the VSD.
Aluminum Adjuvants used in Vaccines
The CDC provides a table showing which vaccines use aluminum-based adjuvants, other adjuvants, or no adjuvant.
Four different aluminum salt forms are listed in the table: AAHS, AH, AP and Alum. Three of these are in vaccines on the CDC’s infant vaccination schedule.
Aluminum Salts in Infant Vaccines
The following table shows the ACVs on the CDC’s infant vaccine schedule, with the most popular brands chosen where applicable. The aluminum-weight in each dose is given, along with the aluminum salt form they use, and the ages at which doses are given.
Al Content (mcg)
Doses Given At (months)
The highest single day exposure is at 2 months old, when 1,225 mcg is injected at once. The total aluminum content of the vaccines given to infants in the first six months is 3,450 mcg (3.45 mg).
Is this a “small” amount?
The CDC writes that:
Aluminum-containing adjuvants are vaccine ingredients that have been used in vaccines since the 1930s. Small amounts of aluminum are added to help the body build stronger immunity against the germ in the vaccine.
The term “small” requires some reference value. Is 3.45 mg in six months a “small” or “large” amount of exposure to aluminum for an infant?
One way to answer this question is to compare it to aluminum exposure from other sources.
Aluminum from Vaccines vs Other Sources
The CDC writes that:
Aluminum is one of the most common metals found in nature and is present in air, food, and water.
We are indeed all exposed to aluminum in our food, drinking water, and air. By knowing the aluminum content of our food, drinking water, and air, we can estimate our total intake. Using estimates of gut and lung bioavailability, we can calculate our total uptake, i.e. how much aluminum is entering our blood.
It can be seen that for some infants, 98% of aluminum exposure over the year comes from their vaccines. If they are exclusively breastfed they will only uptake 50 mcg through their gut over the entire year. Exposure from city air of average quality is only 6 mcg. Even infants fed high-aluminum soy formula or grain-based baby foods will uptake no more than 2,000 mcg of aluminum through their gut. Still a lot less than the 3,450 mcg aluminum they received from their vaccines.
Since vaccines are the primary source of aluminum exposure to infants, it cannot be claimed that the amount of aluminum in vaccines is “small”.
Absorption from Vaccines
The CDC writes that:
Scientific research has shown the amount of aluminum exposure in people who follow the recommended vaccine schedule is low and is not readily absorbed by the body.
The phrase “not readily absorbed by the body” is certainly true in the case of aluminum exposure in food, drinking water, and air. Gut bioavailability (the percentage of intake that enters the blood) is less than 0.3% and lung bioavailability is only 2.0%. Hardly any of the intake from diet and air enters the body; aluminum is not readily absorbed through the guts or lungs.
Vaccines are injected into muscle. There is no way for the aluminum in vaccines to leave the injection site except by entering the systemic circulation. Thus, intramuscular bioavailability of aluminum is necessarily 100%. It is all absorbed by the body, sooner or later.
By “not readily”, the CDC means that it is absorbed slowly. There have been two studies looking at the rate of aluminum absorption from ACVs: Flarend 1997 and Weisser 2019. Both tested both aluminum hydroxide (AH) and aluminum phosphate (AP) injected intramuscularly in animals. They measured blood concentration to estimate the speed of aluminum absorption.
At the rates observed by Flarend, assuming zero-order absorption, AP vaccines take 56 days to be fully absorbed and AH vaccines take 165 days. At the rates observed by Weisser, AP vaccines take 94 days to be fully absorbed and AH vaccines take 369 days. Based on the absorption rates observed by Flarend, all aluminum from infant ACVs is fully absorbed by one year of age.
Daily Aluminum Uptake in Infancy
Is uptake of aluminum from vaccines “low” because of the slow absorption?
We can use the results of Flarend on vaccine absorption to calculate daily aluminum uptake from vaccines throughout infancy. In the chart below, daily uptake of aluminum from vaccines is plotted against uptake from diet and air. The input scenario is full vaccination on the CDC schedule, typical formula-feeding and average urban air quality.
The slow absorption of the aluminum in vaccines does not alter the fact that vaccines are the biggest source of aluminum exposure in infants. At the peak, just after the 6 month shots, infants are exposed to nearly 20 mcg per day. This is the amount entering their bloodstream from each of their vaccine injection sites, like a nicotine patch. Most infants will never be exposed to more than 2 mcg per day from diet and air.
Since vaccines are the primary source of aluminum exposure to infants, it cannot be claimed that the amount of aluminum exposure is “low”.
Uptake from Vaccines v Safety Levels
Perhaps “low” is meant as compared to a safety level. Unfortunately, there are no uptake safety levels for chronic exposure to aluminum.
There are safety levels for oral intake. These have been derived from observations in animal experiments. They are the highest dose of aluminum for which no adverse effects were observed, converted to a Human-Equivalent Dose (HED). The US ATSDR set an oral intake Minimal Risk Level (MRL) of 1 mg/kgbw/day. The WHO JECFA set an oral intake safety level of 0.3 mg/kgbw/day.
These oral intake safety levels can be converted into a uptake safety levels by multiplying them by an assumed gut bioavailability of 0.3%. The units of mcg/kgbw can be converted into mcg using CDC average infant weight charts. The two derived uptake safety levels can then be added to our daily uptake chart:
Uptake from vaccines alone far exceeds the safety level from the JECFA, and gets very close to the safety level from ATSDR. The cumulative impact of vaccines, diet, and air does exceed the ATSDR safety level for most infants. This is especially true of underweight infants and those on a high-aluminum diet.
The Mitkus Paper – The CDC’s Only Defense
The CDC ends it’s paragraph of information about aluminum adjuvant safety with this:
The first link is to a 2011 paper by Robert Mitkus and four of his colleagues at the US FDA. The paper describes a pharmacokinetic model developed for assessing the safety of ACVs in infants. The second link is to a webpage of the FDA, which refers only to the same Mitkus 2011 paper.
The CDC claims that aluminum adjuvant use is safe. Since Mitkus 2011 is the only scientific paper cited by the CDC in regard to aluminum in vaccines, this is presumably the strongest paper they can cite to support their claim. If this paper is shown to have serious flaws, it would be a crippling blow to the scientific case for vaccine adjuvant safety.
I have studied the Mitkus paper in great depth, along with the papers cited therein. I have reconstructed his whole model. I have expanded it to be able to cover more scenarios, i.e. variations in diet, air quality, vaccine schedules, etc. By doing that, I have identified many weaknesses, faulty assumptions, and outright errors.
I will explain the many flaws in the Mitkus model in future posts. In the meantime, here is an infographic explaining the most outrageous error. Mitkus used the wrong retention equation in his model!
The only scientific paper cited by the CDC in defense of their claim that aluminum adjuvants are safe contains this outrageous error, and there are many more.
There are good reasons to be concerned about aluminum adjuvant safety. Aluminum is a neurotoxin that can subtly alter neurodevelopment. It’s use in vaccines has increased over the years, in line with the increase in neurodevelopmental disorders.
The CDC is incorrect in describing the amount of aluminum in vaccines as “small” or total exposure from vaccines as “low”. Vaccines are in fact the primary source of aluminum exposure in infants. The CDC should update their website to remove these inaccurate descriptions.
Aluminum exposure from the vaccines on the CDC’s infant schedule exceeds the safety level established by the WHO. This calls for a reappraisal of the vaccine schedule: delaying or avoiding ACVs to reduce the risk of adverse neurodevelopmental effects from vaccines.
The CDC’s claim that aluminum exposure from vaccines is low enough to be considered safe relies on one single paper: a deeply flawed study by the FDA, presenting a pharmacokinetic model with many serious errors.
As both sides acknowledge, the text of the page is unchanged and still says that “vaccines do not cause ASD”, and that “there is no link between receiving vaccines and developing ASD” and “no links have been found between any vaccine ingredients and ASD”.
ICAN intend to pressure the CDC to remove these statements, too, because they say they are not supported by the scientific evidence.
Let us assess whether ICAN are right by looking at each of the sources cited by the CDC on this page to support their claim that vaccines do not cause autism.
Institute of Medicine, 2012
Under the heading “There is no link between vaccines and autism”, the CDC writes 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. In 2011, an Institute of Medicine (IOM) report on eight vaccines given to children and adults found that with rare exceptions, these vaccines are very safe.
That Institute of Medicine (IOM) report was called “Adverse Effects of Vaccines: Evidence and Causality” (2012) and is a systematic review of all the scientific literature looking adverse effects of vaccines. The eight vaccines included in the study were MMR, Varicella, Influenza, Hepatitis A, Hepatitis B, HPV, DTaP, and Meningococcal. An impressive 76 different health outcomes were included in the study, one of which was autism.
However, only two vaccines – MMR and DTaP – were even examined in relation to the autism health outcome. Presumably, this is because there are no studies to examine. This alone makes the report insufficient evidence to claim that vaccines don’t cause autism. For all but two vaccines, according to the IOM, there have been no studies looking at associations to autism.
Regarding DTaP, the IOM concluded that:
The evidence is inadequate to accept or reject a causal relationship between DTaP and autism.
Their epidemiological assessment found the evidence “insufficient” (just one single study, rejected due to being based on data from a passive reporting system). Their mechanistic assessment found the evidence “lacking” (no studies at all).
The MMR is the only vaccine where the IOM made a conclusive statement:
The evidence favors rejection of a causal relationship between MMR and autism.
At best, therefore, this report supports the claim that the MMR does not cause autism. It cannot possibly support the bigger claim that vaccines do not cause autism.
In their epidemiological assessment, the IOM reviewed an impressive 22 studies looking for an association between MMR and autism. 12 of them were dismissed for being based on data from a passive surveillance system lacking an unvaccinated comparison population, or for being an ecological comparison study lacking individual-level data. A further 5 were dismissed as having “very serious methodological limitations”.
In their mechanistic assessment, the IOM reviewed 6 studies, but dismissed them all for not providing evidence beyond temporality, concluding that the mechanistic evidence is “lacking” when it comes to assessing a causal association between MMR and autism.
This left just 5 epidemiological studies that the IOM considered good enough to be used to conclude the lack of a causal association between MMR and autism. These were the studies by Taylor 1999, Farrington 2001, Madsen 2002, Smeeth 2004, and Mrozek-Budzyn 2010. The Mrozek-Budzyn study was acknowledged by the IOM as having “serious limitations”, and the Farrington study is based on the same data as the Taylor study.
I will review each of these MMR-autism studies in a future post.
The CDC writes that:
A 2013 CDC study added to the research showing that vaccines do not cause ASD. The study looked at the number of antigens (substances in vaccines that cause the body’s immune system to produce disease-fighting antibodies) from vaccines during the first two years of life. The results showed that the total amount of antigen from vaccines received was the same between children with ASD and those that did not have ASD.
The De Stefano study is a helpful addition to the research, in that it looks at the cumulative effects of multiple vaccines, rather than at vaccines in isolation as in the IOM report.
However, the study is deeply flawed, because no one who claims that vaccines cause autism says that it should be related to the number of antigens received. It is the other ingredients of vaccines that are of greater concern, especially the aluminum salts used as adjuvants. Nevertheless, grouping by number of antigens has the potential to act as a proxy for distinguishing fully vaccinated, partially vaccinated, and unvaccinated, so it may not be an entirely worthless measurement.
Unfortunately, the results in the study are skewed by the presence of three vaccines with 3000 antigens (DTP, DTP-Hib, and Typhoid), and then a large drop down to vaccines with 69 antigens (Varicella), 24 antigens (MMR), and all other vaccines having less than 15 antigens. Total number of antigens is therefore merely a proxy for number of doses of high-antigenic vaccines. From the chart below it can be seen that most subjects had either zero, three, or four doses of these high-antigenic vaccines, and this alone determines the groups used in the analysis.
The chart also shows that there were no unvaccinated subjects in the study. Nobody received less than 50 antigens. The group that received zero high-antigenic vaccines received many other vaccines, because most of them had between 151 and 311 antigens. During the study period, the high-antigenic DTP vaccines were replaced by low-antigentic DTaP vaccines, so most of those in the “low antigens” group were fully vaccinated, just like most of the subjects in all the other groups.
At best, this study can be used to support the claim that high-antigenic vaccines do not cause autism any more than low-antigenic vaccines do. Since there are no high-antigenic vaccines used anymore, this is a moot conclusion. This study certainly cannot be used to support the claim that vaccines do not cause autism, because there were no unvaccinated subjects in the study.
The CDC then has a heading of “Vaccine ingredients do not cause autism” and writes that:
One vaccine ingredient that has been studied specifically is thimerosal, a mercury-based preservative used to prevent contamination of multidose vials of vaccines. Research shows that thimerosal does not cause ASD. In fact, a 2004 scientific review by the IOM concluded that “the evidence favors rejection of a causal relationship between thimerosal–containing vaccines and autism.” Since 2003, there have been nine CDC-funded or conducted studies that have found no link between thimerosal-containing vaccines and ASD, as well as no link between the measles, mumps, and rubella (MMR) vaccine and ASD in children.
That Institute of Medicine (IOM) report was called “Immunization Safety Review: Vaccines and Autism” (2004) and is a systematic review of all the epidemiology studies looking at associations between vaccines and autism. The report only examines studies of thimerosal-containing vaccines (TCVs) and the MMR vaccine (superceded by their 2012 review).
The IOM reviewed 12 studies looking for an association between TCVs and autism. 6 of them were dismissed for being based on data from a passive surveillance system lacking an unvaccinated comparison population, or for being an ecological comparison study lacking individual-level data. One study based on Vaccine Safety Datalink (VSD) data was dismissed as “uninterpretable”.
This left 5 studies on which the IOM relied for their conclusion that TCVs do not cause autism: Hviid 2003, Miller 2004, Verstraeten 2003, Madsen 2003, Stehr-Green 2003.
The CDC cites a two-page PDF that lists and briefly summarises eight further studies to support their claim TCVs do not cause autism: Barile 2011, Price 2010, Tozzi 2009, DeStefano 2009, McMahon 2008, Thompson 2007, Verstraeten 2003, Stehr-Green 2003 (included twice).
I will review each of these TCV-autism studies in a future post.
Thimerosal Removed From Vaccines
The CDC writes that:
Between 1999 and 2001, thimerosal was removed or reduced to trace amounts in all childhood vaccines except for some flu vaccines. This was done as part of a broader national effort to reduce all types of mercury exposure in children before studies were conducted that determined that thimerosal was not harmful. It was done as a precaution. Currently, the only childhood vaccines that contain thimerosal are flu vaccines packaged in multidose vials. Thimerosal-free alternatives are also available for flu vaccine.
Thus, the question of whether TCVs cause autism is now only of historical interest within the wider context of the question of whether vaccines cause autism. The studies cited to support that the claim that TCVs do not cause autism have significant weaknesses, and there is considerable evidence suggesting that TCVs do cause autism.
Since they are now rarely used, TCVs are clearly not an ingredient of concern to those who claim that vaccines cause autism today. Therefore, whether TCVs do cause autism is a moot point in respect of this present-tense claim.
Besides thimerosal, no other vaccine ingredients are named. All the ingredients in vaccines today are addressed by the CDC with a single sentence:
Besides thimerosal, some people have had concerns about other vaccine ingredients in relation to ASD as well. However, no links have been found between any vaccine ingredients and ASD.
No studies at all are cited to support this claim. The link goes to a page merely listing types of vaccine ingredients and their purpose:
Aluminum salts are the vaccine ingredient of biggest concern when it comes to autism, because aluminum is a neurotoxin that has been observed to induce subtle neurological effects and autism-like behaviour in animals exposed to it. The toxic nature of aluminum is why aluminum salt works as a vaccine adjuvant, ensuring that the activation of the immune system is strong enough to result in immunological memory.
There have also been health concerns raised about formaldehyde, glutamate, polysorbate-80, antibiotics, animal cells and fetal cells.
No studies are cited on this page to support the claim that vaccine ingredients do not cause autism.
The first link is to a meta-analysis that combined the results of five MMR-autism studies, and five TCV-autism studies, all of which individually found no associations. Most of the studies in this Taylor 2014 meta-analysis are the same papers reviewed by the IOM, cited above (including some they rejected for having serious methodological limitations); there is one new TCV study (Andrews 2004) and one new MMR study (Uno 2012).
The second link is to an ecological study, Schechter 2008, showing the removal of TCVs did not coincide with any reduction of cases of autism in California. The third link is to the IOM 2004 Report cited above. The fourth link is to the Hviid 2003 study of TCVs-autism. The fifth link is to the Madsen 2002 study of MMR-autism, both in the IOM Reports cited above. The sixth link is to an outdated review of TCVs that does not reference autism. The seventh link is to a statement by the AAP regarding removing thimerosal from vaccines.
There is no evidence cited on the CDC’s “Autism and Vaccines” page to support their claim that vaccines do not cause autism. The only evidence cited relates either to one single vaccine: the MMR, or to one single vaccine ingredient: thimerosal. Even if this evidence is accepted, it does not follow that vaccines do not cause autism.
More studies are needed in order to determine whether vaccines cause autism, starting with the most basic kind: epidemiological studies that compare health outcomes in vaccinated and unvaccinated children.
Interestingly, this was pointed out by the IOM itself in their 2013 report “The Childhood Immunization Schedule and Safety”:
Without any studies looking at autism as a health outcome and comparing vaccinated and unvaccinated groups, there is no support for the CDC’s claim that vaccines do not cause autism. They were right to change the title of their page. They now need to correct the rest of it.
Atladottir, 2010: admission to hospital due to maternal viral infection in the first trimester and maternal bacterial infection in the second trimester were found to be associated with diagnosis of ASDs in the offspring https://www.ncbi.nlm.nih.gov/pubmed/20414802
Vargas, 2005: The brains of people with ASD show a marked activation of microglia and astroglia, and cytokine profiling indicated that MCP-1 and TGF- β1, derived from neuroglia, were the most prevalent cytokines. Cerebrospinal fluid showed a unique proinflammatory profile of cytokines, including a marked increase in MCP-1. https://www.ncbi.nlm.nih.gov/pubmed/15546155
Choi, 2016: Either MIA or direct administration to the fetal brain of mice of inflammatory cytokine IL-17a promotes abnormal cortical development and ASD-like behaviors in offspring https://www.ncbi.nlm.nih.gov/pubmed/26822608
William Thompson is the CDC whistleblower who revealed that he had been involved in a cover-up of a key result in the vaccine-autism debate.
He was referring to the DeStefano 2004 study of MMR and autism, on which Thompson was a co-author, conducting the statistical analysis. Thompson claimed that an association between MMR and autism in African American boys was identified in the data, but that the finding was omitted from the final paper. He cited the pressure to show no association between MMR and autism, and explained how they tried various statistical techniques to try to hide the association.
The infographic above presents the data behind the debate. Brian Hooker’s 2014 re-analysis of the data shows there is indeed an association between MMR and autism in African American boys in the data.
Forget the politics; the science here is telling us there is an association between a vaccine and autism.
In 2012, the Institute of Medicine (IOM) released a comprehensive evidence review entitled “Adverse Effects of Vaccines: Evidence and Causality”.
They looked at 8 different vaccines and 76 different adverse events. One of these adverse events was autism.
For 1 vaccine (MMR), the IOM favored rejection of a causal relationship.
For 1 vaccine (DTaP), the IOM declared the evidence inadequate to accept or reject a causal relationship.
For the other 6 vaccines in the review, the IOM did not look for any evidence regarding a causal relationship.
Clearly then, the correct conclusion of this evidence is NOT that “vaccines do not cause autism”. There is not enough evidence to make that conclusion.
Even if a causal relationship between MMR and autism is rejected, it does not follow that “vaccine do not cause autism” because MMR is only one of 8 or more vaccines, and the evidence is inadequate to accept or reject a causal relationship for them. There have also been no studies looking for associations between cumulative vaccinations, or different timings, or different combinations of vaccines, and autism.
The CDC cites this IOM report for its claim that “vaccines do not cause autism” and yet this report does not support this claim.
Our understanding and conception of autism has changed considerably
over the years, as shown in the infographic above.
Autism Before 1980
The first recognition of autism only occurred in 1943, and for decades it was believed to be very rare, affecting only 1-in-10,000 children. The first time the American Psychiatric Association (APA) published their list of all known mental disorders, the prestigious Diagnostic and Statistical Manual of Mental Disorders or DSM-1 (1952), it did not include autism. It used the word autistic only in reference to one of the behaviours associated with childhood-onset schizophrenia. Autism was also not listed in the second edition, DSM-2 (1968).
Autism in DSM-3
Autism was first listed as a known mental disorder in DSM-3
in 1980. A category of neurodevelopmental
(early onset) disorders was created called the Pervasive Development
Disorders (PDDs), which contained infantile autism for when autistic
behaviours appeared before 30 months of age and childhood onset PDD for
when they appear after 30 months of age.
These autistic behaviors include lack of responsiveness to
other people, deficits in language development and social relationships,
resistance to change, attachment to inanimate objects, anxiety and panic
attacks, inappropriate fear or rage reactions, oddities of motor movement, and
speech and hyper-sensitivity to sensory stimulation.
A third PDD was atypical autism, a catch-all for when
there were impairments in social skills and language but the criteria for a specific
PDD cannot be met.
Autism in DSM-4
The DSM-4 in 1994 introduced three areas of diagnosis for the
PDDs: impairments in social interaction, impairments in communication, and
restricted, repetitive and stereotyped patterns of behavior, interests and
activities. It also renamed and reformulated
Autistic Disorder required onset before 36 months of
age and at least 6 of the 12 impairments listed across the three areas of
diagnosis. Those previously diagnosed with
infantile autism would in the new system likely be diagnosed with autistic
disorder. Those previously diagnosed
with childhood onset PDD or atypical autism would likely be diagnosed with PDD-NOS
(for Not Otherwise Specified), the new catch-all for where there are severe
deficits in one of the three areas of diagnosis but the criteria are not met
for any of the specific PDDs.
Three new PDDs were added: Asperger’s Disorder was
created for those with impairments in social interaction and restricted
behaviours, but no impairments in communication, cognition or language skills,
and it was considered “mild autism” or “high-functioning autism”. The other two new additions were Childhood
Disintegrative Disorder (CDD), a sudden and severe regressive disorder in
multiple areas of functioning with subsequent onset of autistic behaviors, and Rett’s
Disorder, a regressive disorder affecting head growth, motor skills, gait
and trunk movements, as well as autistic behaviours. These are both very rare disorders, and Rett’s
Disorder is now considered a genetic brain disorder rather than an autism
spectrum disorder or PDD.
Asperger’s makes up 17% of cases of PDD, autistic disorder is
31%, but the largest group is PDD-NOS at 53% (Hviid, 2019). The addition of Asperger’s Disorder (and to a
much lesser extent, CDD and Rett’s) would thus have caused only a small step
change – ceteris paribus – in the number of people diagnosed with a PDD, as
DSM-4 replaced DSM-3.
Autism in DSM-5
The DSM-5 in 2013 replaced the PDD category entirely and
replaced it with Autism Spectrum Disorder (ASD). The PDDs were already considered a spectrum
widely known as the autism spectrum, ranging from the most severe (Autistic Disorder)
to the less severe (PDD-NOS and Asperger’s).
Autism was no longer the name of one type of PDD, but the whole category,
and it was defined as a single spectrum disorder rather than a category of related
disorders with distinct names, as PDD had been.
Within ASD, there is a classification by severity in two
dimensions: 1) deficits in social interaction and communication, and 2)
restricted, repetitive behavior, interests, or activities. Three severity levels (mild, moderate
and severe) are defined by how much support the individual requires. Most of those previously diagnosed with
autistic disorder would now be diagnosed with moderate or severe ASD (aka autism),
while most of those previously diagnosed with Asperger’s disorder would now be
diagnosed with mild or moderate autism. It
is possible to be diagnosed as having one severity level for social deficits
and a different severity level for restricted behaviors, giving nine possible severity
level combinations within the spectrum.
The DSM-5 also created a new neurodevelopmental disorder
called Social (Pragmatic) Communication Disorder (SCD) for cases that
meet the social deficits criteria for ASD but not the restricted behaviors criteria. According
to one study (Kim, 2014), only 63% of those with a previous diagnosis of PDD-NOS
meet the DSM-5 criteria for ASD, with 32% lacking the restrictive behaviours criteria
and so would now be diagnosed with SCD, not ASD. Those previously diagnosed with PDD-NOS who
do meet the ASD criteria are likely to have either a mild or moderate DSM-5 severity
level (Walker, 2004).
The impact of a third of those with PDD-NOS (the largest PDD
disorder) being taken out of the umbrella of ASD should have a noticeable
decrease – ceteris paribus – in autism diagnoses as DSM-5 replaces DSM-4. The definition of ASD in DSM-5 is tighter
than the definition of PDD in DSM-4 and may be tighter than the definition of
PDD in DSM-3 as well.
Autism in ICD-10 Codes
The World Health Organisation (WHO) maintains a comprehensive
medical coding system known as the International Classification of Diseases
(ICD). The current iteration of this
system is ICD-10, which has been used since 1994. Chapter 5 contains the codes for mental and
behavioural disorders (F00-F99) and it has codes for “childhood autism” (F84.0),
“atypical autism” (F84.1) and Asperger’s disorder (F84.5), “Other PDD” (F84.8)
and “Unspecified PDD” (F84.9) all within the category of pervasive development
These five ICD-10 codes are considered to cover the whole
autism spectrum and epidemiological studies of autism generally define an
outcome of autism as a diagnosis with one of these five ICD-10 codes (for
example, Hviid 2019).
These codes map easily to the disorders in DSM-4 and DSM-3:
childhood autism is the same as infantile autism (DSM-3) and autistic disorder
(DSM-4); Asperger’s Disorder is defined the same way as in DSM-4; PDD-NOS (DSM-4)
is split between ICD codes for atypical autism, other PDD and unspecified PDD,
with atypical autism being defined in a way similar to the DSM-3 definition.
Autism Diagnostic Criteria
Despite the many taxonomical changes within the PDD / ASD category
of disorders over the years, the diagnostic criteria have been refined and
elaborated with each iteration of the DSM, but the basic idea has always been
the same. Autism has always been defined
as a disorder with two fundamental defining elements: deficits in social
communication and social interaction, and restricted, repetitive patterns of
behavior, interests and activities.
DSM-5 gives the clearest diagnostic criteria for each of
these two elements. It provides three
illustrative examples of social deficits, all of which must be met for a
diagnosis, and four illustrative examples of restricted behaviors, two of which
must be met for a diagnosis. The
Persistent deficits in social communication and social interaction across multiple contexts, as manifested by ALL OF the following, currently or by history:
Deficits in social-emotional reciprocity, ranging, for example, from abnormal social approach and failure of normal back-and-forth conversation; to reduced sharing of interests, emotions, or affect; to failure to initiate or respond to social interactions.
Deficits in nonverbal communicative behaviors used for social interaction, ranging, for example, from poorly integrated verbal and nonverbal communication; to abnormalities in eye contact and body language or deficits in understanding and use of gestures: to a total lack of facial expressions and nonverbal communication.
Deficits in developing, maintaining, and understanding relationships, ranging, for example, from difficulties adjusting behavior to suit various social contexts; to difficulties in sharing imaginative play or in making friends; to absence of interest in peers.
Restricted, repetitive patterns of behavior, interests, or activities as manifested by AT LEAST TWO of the following, currently or by history:
Stereotyped or repetitive motor movements, use of objects, or speech (e.g., simple motor stereotypies, lining up toys or flipping objects, echolalia, idiosyncratic phrases).
Insistence on sameness, inflexible adherence to routines, or ritualized patterns of verbal or nonverbal behavior (e.g., extreme distress at small changes, difficulties with transitions, rigid thinking patterns, greeting rituals, need to take same route or eat same food every day).
Highly restricted, fixated interests that are abnormal in intensity or focus (e.g., strong attachment to or preoccupation with unusual objects, excessively circumscribed or perseverative interests).
Hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of the environment (e.g., apparent indifference to pain/temperature, adverse response to specific sounds or textures, excessive smelling or touching of objects, visual fascination with lights or movement).
For a diagnosis of ASD, symptoms must also be present in the
early developmental period (but may not become fully manifest until
social demands exceed limited capacities, or may be masked by learned
strategies in later life), they must cause clinically significant impairment
in social, occupational, or other important areas of current functioning, and these
disturbances are not better explained by intellectual disability or global
The requirement for onset during the “early developmental period,”
meaning early childhood, obviously means that adults cannot develop autism. However, adults can be and are diagnosed with
autism if they are impaired significantly enough by their social deficits and
repetitive behaviors today to warrant a diagnosis, without any evidence that
their autistic behavior started in the early developmental period. The age of onset diagnosis criteria is
essentially ignored as it is assumed that any adult that meets the criteria for
autism today must have been autistic their whole life.
The requirement for “clinically significant impairment” is
standard wording throughout the DSM-5 for all mental disorders. It means that it is left entirely at the
discretion of clinicians to judge whether a child (or adult) is impaired *significantly
enough* by his social deficits and repetitive behaviors to get a diagnosis of ASD. Clinicians get to draw the line between marginal
cases of mild ASD and no ASD, and where they draw that line is flexible and may
have changed over time to include more people: an adult previously considered merely
as having autistic-like traits (perhaps an introvert with restricted interests,
a geek or an eccentric) may now get a diagnosis of ASD, if he seeks one. There are incentives for adults to get a diagnosis,
for parents and schools to have their children diagnosed, and for clinicians to
give diagnoses in marginal cases. There
is a clear danger of over-diagnosis of autism due to the flexibility of the clinical
significance requirement, and this must be borne in mind when looking at
historical statistics of autism prevalence and incidence.
Clear and well-understood definitions are essential for
productive discussion and good science. When
discussing autism, it is important that all the participants understand whether
the term is being used:
in the wider sense of anyone on the autism spectrum in the DSM-5 conception, roughly equivalent to what DSM-4 called PDDs
in the narrower sense of autistic disorder (only 31% of PDDs) in the DSM-4 conception, roughly equivalent to severe autism in the DSM-5 conception.
The wider sense includes those with Asperger’s (17%) and PDD-NOS (53%), which are likely mild or moderate autism in the DSM-5 conception.
When discussing autism, when reviewing data from epidemiological studies, comorbidity studies, historical trends, independence surveys, and so on, it is crucial to understand if the data refers to the whole autism spectrum or just those with severe autism, or those with autism and some other condition comorbid with autism, such as a language disorder or intellectual disability.