Originally posted April 24th 2019, Updated April 28th 2021.
In our previous piece, we showed how Andrew Wakefield fabricated data claiming that the MMR vaccine caused autism. The fallout of this fabrication―the birth of the modern “anti-vaxxer” movement―continues to exert its influence on public health to this day. Subsequent to Wakefield’s studies and claims, researcher’s started investigating the links between the MMR vaccination and autism. This point cannot be overstated. Scientists responded, and they did so by using the scientific method and with the provision of data.
Three distinct hypotheses were tested based on Wakefield’s fabricated data and the subsequent fear mongering and public skepticism that followed.
TL;DR Vaccines work and save lives!
1) Does the combination measles-mumps-rubella (MMR) vaccine cause autism?
Twelve epidemiological studies (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12), the most recent in 2019, were conducted and the conclusions of these studies are stated below.
TL;DR: No link exists between the MMR vaccine and autism
“Over a decade’s effort to detect all severe adverse events associated with MMR vaccine could find no data supporting the hypothesis that it would cause pervasive developmental disorder or inflammatory bowel disease.”
“Data do not support a causal association between MMR vaccine and autism. If such an association occurs, it is so rare that it could not be identified in this large regional sample.”
“Comprehensive analysis of the reported adverse reactions established that serious events causally related to MMR vaccine are rare and greatly outweighed by the risks of natural MMR diseases.”
“Our results….provide further evidence against a causal association between MMR vaccination and autism.”
“The data provide evidence that no correlation exists between the prevalence of MMR vaccination and the rapid increase in the risk of autism over time.”
“These data do not suggest an association between MMR immunization among young children and an increase in autism occurrence.”
“No evidence was found to support a distinct syndrome of MMR-induced autism or of “autistic enterocolitis.” These results add to the recent accumulation of large-scale epidemiologic studies that all failed to support an association between MMR and autism at population level.”
“This study provides strong evidence against the hypothesis that MMR vaccination causes autism.”
“This study provides strong evidence against the hypothesis that MMR vaccination causes autism.”
“There was no evidence that onset of autistic symptoms or of regression was related to measles-mumps-rubella vaccination.”
“The findings ruled out an association between pervasive developmental disorder and either high levels of ethylmercury exposure comparable with those experienced in the United States in the 1990s or 1- or 2-dose measles-mumps-rubella vaccinations.”
“The study strongly supports that MMR vaccination does not increase the risk for autism, does not trigger autism in susceptible children, and is not associated with clustering of autism cases after vaccination.”
2) Does thimerosal, an ethyl mercury-containing preservative in some vaccines, cause autism?
“Thimerosal is a mercury-based preservative that has been used for decades in the United States in multi-dose vials (vials containing more than one dose) of medicines and vaccines. There is no evidence of harm caused by the low doses of thimerosal in vaccines, except for minor reactions like redness and swelling at the injection site. However, in July 1999, the Public Health Service agencies, the American Academy of Pediatrics, and vaccine manufacturers agreed that thimerosal should be reduced or eliminated in vaccines as a precautionary measure.” Source: CDC
The above summary from the CDC nicely summarizes why thimerosal is used and why a decision was made to remove thimerosal from vaccines, particularly those vaccines administered to children. However, in order to understand why those choices were made as well as the impact of those choices, one needs to consider the historical context.
Imagine in the news you hear that the widely used MMR vaccine in children is causing autism and then the government issues a precautionary directive (i.e., in the absence of any data) which bans mercury products from vaccines. This is sufficient to produce the birth of modern “anti-mercury/anti-vaxxer” groups.
Fact: Measles, mumps, and rubella (MMR), Varicella (chickenpox), inactivated polio (IPV), and pneumococcal conjugate vaccines do not and never did contain thimerosal.
At the time when this precautionary directive was issued, the US was also investigating sources of mercury in food and drugs. In particular, methylmercury was identified as a trace-element heavy metal which can cross the blood brain barrier and which causes debilitating developmental defects. Thimerosal, which contains by weight 50% of a different mercury compound, ethylmercury, was also being scrutinized.
Part of the reason for this scrutiny, and the later issuance of a precautionary directive, was because the long term developmental effects of ethylmercury were unknown. Again, scientists responded with research studies and data!
Fact: The primary source of methylmercury to humans is via consumption of fish.
First, epidemiological studies (1, 2, 3, 4, 5, 6) were conducted. These studies, respectively, concluded:
TL;DR: No link exists between the low level of thimerosal (50% ethylmercury) used in vaccines and autism
“The body of existing data, including the ecologic data presented herein, is not consistent with the hypothesis that increased exposure to Thimerosal-containing vaccines is responsible for the apparent increase in the rates of autism in young children being observed worldwide.”
“The discontinuation of thimerosal-containing vaccines in Denmark in 1992 was followed by an increase in the incidence of autism. Our ecological data do not support a correlation between thimerosal-containing vaccines and the incidence of autism.”
“The results do not support a causal relationship between childhood vaccination with thimerosal-containing vaccines and development of autistic-spectrum disorders.”
“No consistent significant associations were found between TCVs and neurodevelopmental outcomes.”
“We could find no convincing evidence that early exposure to thimerosal had any deleterious effect on neurologic or psychological outcome.”
“With the possible exception of tics, there was no evidence that thimerosal exposure via DTP/DT vaccines causes neurodevelopmental disorders.”
Secondly, animal based studies in a variety of species, including mice, rats, and primates were conducted in order to understand how long ethylmercury stays in the body and where it may end up (e.g, excreted or in the brain). This invaluable animal research could only have been done in animals–and for obvious reasons. The results of these studies have shown that the body eliminates thimerosal easily after breaking it down into its constituents, ethylmercury and thiosalicylate. The result of all of this research has led the CDC to declare the use of thimerosal in vaccines safe.
3) Does receiving too many vaccines cause autism?
TL;DR: No link exists between the number of vaccines received and autism
When studies of the MMR vaccine and of ethylmercury in thimerosal failed to show a link to autism, alternate conspiracy theories emerged. Primary among them was the notion that children receive far too many vaccinations today, which may overwhelm the immune system and puts them at risk for the development of certain diseases such as autism. One case in particular, the Hannah Poling case, fueled an already tenuous situation where mistrust and uncertainty pervaded public opinion.
To understand this scenario completely, however, one must again consider the broader historical context. It is absolutely true that in comparison to 100 years ago, when children received only one vaccination (smallpox), at present children may receive as many as 20 vaccines by the time they are two years of age. However, following Wakefield’s devastating influence on public perceptions of vaccination, and an American populace with a penchant for suing, the federal government stepped in to create the National Childhood Vaccine Injury Act which included the Vaccine Injury Compensation Program (VICP). In the years immediately following its formation, the VICP program proved valuable–ensuring that scientific evidence must support the notion that vaccines cause the purported adverse event.
This all changed in 2005, when Margaret Althen claimed that her optic neuritis was a consequence of receiving a tetanus vaccine. Here, the court ruled that if the petitioner proposed a biological plausible mechanism (independent of support from scientific evidence) by which a vaccine causes harm, along with a documented sequence of cause and effect, then an award could be granted. Other cases and awards followed, such as Dorothy Werderitsch in 2006, and then Hannah Poling in 2008.
Hannah Poling, when 19 months old, received five vaccines: diphtheria–tetanus–acellular pertussis, Haemophilus influenzae type b (Hib), measles–mumps–rubella (MMR), varicella, and inactivated polio. Two days after being vaccinated she was “lethargic, irritable, and febrile. Ten days after vaccination, she developed a rash consistent with vaccine-induced varicella. Months later, with delays in neurologic and psychological development, Hannah was diagnosed with encephalopathy caused by a mitochondrial enzyme deficit.” Hannah’s symptoms were consistent with autism–deficits in language, communication and behavior. Her parents sued for compensation under the VICP and won.
Mitochondrial enzyme deficit (MED), is an autosomal recessive disease–meaning that both of Hannah’s parents each carried a single copy of a gene that they passed on to Hannah, leading to her having two copies of that gene and in turn, MED. The first point here is that her vaccinations did not cause MED. The second point deals with whether being vaccinated exacerbated the symptoms of MED–the crux of the VICP ruling. It has been convincingly argued that the VICP ruling was logically flawed:
- There was and continues to be no scientific evidence which supports the notion that vaccines can exacerbate symptoms of encephalopathy
- Hannah presented with other immunological challenges unrelated to vaccinations and that were unusual for a child of her age
- It should also be critically considered whether withholding vaccinations for diseases that are present in the general population, such as chicken pox and whooping cough, would likely to have caused other debilitating effects
- There is no evidence which suggests that multiple vaccines can overwhelm or weaken the immune system.
Fact: In 2010, The VICP announced the Omnibus Autism Proceeding and concluded that vaccines do not cause autism. All pending autism claims to the VICP were rejected.
This last point–whether multiple vaccines can overwhelm or weaken the immune system–is worth special consideration. Even though the immune system of an infant is undeveloped, it has the potential capacity to respond to thousands of vaccines simultaneously. Relatedly, even though the number of vaccines a child receives has increased in recent years, modern vaccines contain fewer antigens (antigens were explained in the first part of this series) because of improvements in the manufacturing process. For example, the smallpox vaccine, 100 years ago, contained over 200 different antigens. In comparison, the 14 vaccines commonly given to young children, in total, contain only 150 antigens. This means that in the modern vaccination era our immune system is activated to a lesser extent that in the past. This also means that if multiple vaccinations overwhelm the immune system — we should have seen it a long time ago when far fewer vaccinations were given, but where many more antigens were present.
In our next piece, we will explore how anti-vaxxer sentiments coupled with four years of side-lining science under the Trump administration, has lead to a deep mistrust of science culminating in COVID-19 #VaccineHesitancy.