The issue of whether routine vaccines cause autism typically arises from the fact that the onset of autism generally occurs at around the same time that children undergo a series of vaccinations designed to protect them against serious diseases.
The exact schedule varies from country to country but commonly includes vaccines for Polio, meningitis, and Rotavirus, amongst several others.
One vaccine that is of particular concern to anti-vaccine campaigners is the MMR vaccine which seeks to immunise children against Measles, Mumps and Rubella.
The World Health Organisation recommends that these vaccines be given in a combined dose, usually on two separate occasions. According to the recommendations, the first dose is commonly given when the child is between 9 and 12 months old, with the second dose administered 6 months later when the child is between 15 and 18 months old.
Autism symptoms usually begin to present between 18 and 36 months. Common effects include difficulty communicating, social impairments and other behavioural problems.
Read: Link between autism and anti-depressants questioned
Controversy reached a head in 1998 after a paper was published in respected British medical journal The Lancet. Authored by Andrew Wakefield, the paper studied twelve children suffering from developmental disorders in London.
Wakefield claimed that the children’s autism was caused by receiving the MMR vaccine, and that it would be safer to administer the three vaccines separately from each other, pending further investigation.
The paper generated substantial controversy over the following years, prompting scores of parents to choose not to vaccinate their children against these diseases. This resulted in an upswing in incidences of the illnesses and a corresponding rise in children's deaths from them.
Read: MMR vaccines - what are the risks?
However, the paper fell into disrepute in 2004 after investigative reporter Brian Deer revealed in the Sunday Times (Read The Guardian's analysis of the report) that Wakefield had several undeclared conflicts of interest. This included R975 000 (£55 000) from a law firm seeking evidence for cases against vaccine manufacturers.
Wakefield was also charged with manipulating evidence and breaching ethics codes. Strikingly, he admitted to taking blood samples from children at his son’s birthday party, paying them £5 each.
The paper was fully retracted in 2010 and Wakefield was stripped of his medical license. The controversy has been called “the most damaging medical hoax of the past 100 years”. Wakefield is still not allowed to practice medicine.
Watch: CNN's Anderson Cooper questions Andrew Wakefield on his claims
Following the original publication of the paper, several international bodies conducted large-scale studies to determine the veracity of the claims.
These studies were undertaken by, amongst others, the CDC (Centers for Disease Control in the US), NHS (National Health Service in the UK), the US Institute of Medicine and the American Academy of Paediatrics.
Watch Part 2 of Anderson Cooper's interview with Andrew Wakefield
None of the studies found any link between autism and the MMR vaccine and the scientific consensus is strongly in favour of this conclusion as summarised by the Autism Science Foundation.
So, why has the issue come to light again?
New information, and new revelations, appear to show in a critical light the results of one of these studies, namely the CDC’s 2004 report into the importance of the age at which children received the MMR vaccine. If results from this report prove to be true, it could thrust the entire medical world into crisis.
A whistleblower from inside the agency, Dr. William Thompson, has come forward to claim that the data in the study was manipulated to show a much smaller correlation than there actually was. Dr. Thompson is a senior researcher for CDC and co-authored the study in question, reported Natural News.
Read: Autism or Asperger's?
This potentially groundbreaking development was brought to light by Dr. Brian Hopper, a leading member in the anti-vaccine movement who communicated with Dr. Thompson.
A video was produced showing some of the communications between the two men. This video was hosted by Autism Media Channel, an organisation operated by the discredited Andrew Wakefield.
Well-known South African scientist Tim Noakes also waded into the debate when he tweeted a link to the video with the comment "Dishonest science?".
However, he has since distanced himself from the anti-vaccine movement stating that he was simply drawing attention to the fact that not all science should be taken at face value.
Specifically, the video claims that the data the CDC omitted from its study showed a 340% higher rate of autism amongst African-American boys who received the vaccine before 36 months of age.
This is of course a statistically significant result that would have major implications for healthcare across the globe.
However, this revelation is not as clear-cut as it may seem. For starters, the 340% increase came from a reanalysis of the data by Dr. Hopper who presented his findings in the little-known journal Translational Neurodegeneration.
The prominent medical blog Science-based Medicine (SBM) subsequently posted a detailed explanation of the flaws in Dr. Hopper’s reanalysis, most of which boil down to one key point:
The original study followed a case-control design, a common type of study which takes a group of people who fulfil a condition (having autism, in this case) and matches them as closely as possible with another group who do not. The second group is known as a control group.
The author of the SBM blog post, however, posits that Dr. Hopper interpreted the data as if it had come from a different kind of study design, namely a cohort study. A cohort study follows a group of people over time and notes how many of them develop the condition.
Read: Living with autism
To make things clearer, in this instance a cohort study would have followed a group of children over time, noted when they received the MMR vaccine and which of them developed autism.
However, because the data collected for the study was collected for a case-control design, it intentionally included a higher-than-normal number of children with autism than it would have if it had been collected for a cohort study. This, according to SBM, confounded Dr. Hopper’s reanalysis and made his conclusions invalid.
Immediate, serious action
As a result, the study has now been retracted by Translational Neurodegeneration citing "serious concerns about the validity of it conclusions".
Concerns have also been raised that Dr. Hopper did not seek out an epidemiologist to co-author the study with him, something that would certainly have helped with the statistical work involved.
Technicalities aside, though, the key question brought about by this revelation is why the CDC would want to hide this result. Given that the CDC’s job, according to their name, is to control and prevent diseases, such a result would be incredibly important and provoke immediate, serious action.
The general argument amongst anti-vaccine proponents is that there is collusion between the CDC and the pharmaceutical companies who produce the MMR vaccine.
If such a result were to come out, it would remove a substantial revenue source for these companies as well as open them up to potential litigation.
However, if this were to be true, it would also entail that many other such organisations were also in on this conspiracy, including those in other nations such as Britain’s National Health Service.
A paper released in July reviewed 166 well-designed, independent studies into the safety and efficacy of vaccines.
Read the paper: Safety of Vaccines Used for Routine Immunization in the United States
They found no correlation at all between vaccines, including MMR, and autism, as reported by Vox. Do we believe that these 166 studies were all authored by individuals inside this conspiracy?
The likelihood of such despicable deception on such an unfathomably large scale is so improbable as to be virtually impossible.
Read: Obesity in pregnancy an autism risk
For his part, Dr. William Thompson, the whistleblower, has released a statement through his lawyers. In it he reaffirms that “my coauthors and I omitted statistically significant information in our 2004 article... the omitted data suggested that African American males who received the MMR vaccine before age 36 months were at increased risk for autism.”
He also states that he “would never suggest that any parent avoid vaccinating children of any race.”
No significant link to autism
The real story behind Thompson’s revelations is likely to be an interesting one, and one that has certainly not yet been told accurately and in full.
However, due to the obvious legal sensitivities of this, it may take months or years before the truth actually comes out.
What is certain is that the MMR vaccine has been shown to be highly effective in reducing incidences of these diseases, and correspondingly the number of deaths from them.
It has also been shown time and time again to not have any significant link to autism.
Anti-vaccine proponents have also not suggested what the causal link between the vaccine and autism is. Without any idea as to how the vaccine would cause autism, it is difficult for scientists to investigate and further.
Could brain damage be the real cause of autism?
In particular, damage to the cerebellum is thought to be key. The cerebellum is a relatively small and “primitive” part of the human brain, but due to the fact that it affects many, many other areas of the brain, damage it could result in problems in other areas of the brain and that, in turn, could be the cause of the cognitive development and social difficulties that characterise autism.
Wang further cites a 2007 paper in the journal Pediatrics that found that individuals who experienced cerebellum damage at birth were 36 times more likely to score highly on autism screening tests. They also reference studies in 2004 and 2005 that found that the cerebellum is the most frequently disrupted brain region in people with autism.
Wang told The Daily Beast: "Because the risk factor from cerebellar injury is bigger than any other known environmental risk, we think this provides deep insight into the basic biology of how ASD brains go off track,”... “Problems in cerebellar function (whether caused by injury or genetic mechanisms) aren’t the cause of autism, but they are potentially a significant cause of autism.”
Graph: Likelihood of presenting autism vs possible cause, from Princeton University. Researchers' review of existing research found that a cerebellar injury at birth can make a person 36 times more likely to score highly on autism screening tests, and is the largest un-inherited risk.
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