Although the increasing incidence of autism has been linked to some aspect of vaccination – perhaps thimerosal – the scientific evidence does not strongly support a causal relationship; instead, the causes for the increase may arise, for example, from improved recognition and diagnosis of this still poorly understood condition.
Increased concern has been expressed over the rise in autism in recent decades
There has been increased concern over the rise in autism in recent decades. Autism was first described and identified as a disorder in the 1940s (Kanner, 1943). The diagnosis has been noted more frequently in recent decades. In the 1990s most particularly, parents began to report anecdotally that they noted symptoms of autism symptoms and received diagnoses of autism when their children had passed 18 months of age. This point in a child’s growth and development was also the time when vaccines are routinely administered.
The rise in autism was linked in a public discussion with vaccination
This rise in autism was thus linked in a public discussion with vaccination. Parents made a causal connection between the timing of routine vaccinations and the onset of autism symptoms that they observed. Parents’ concerns were exacerbated in the 1990s by the fact that the Federal Food and Drug Administration acknowledged the fact that some vaccine preparations contained thimerosal. Thimerosal, used as a preservative in some vaccine preparations, contains ethylmercury.
Ethylmercury, as might be guessed from the mercury in its name, is a known toxin. Making a connection between vaccines and autism was challenged by the lack of information and understanding of autism’s etiology, whether vaccines are involved or not. Several possible mechanisms to explain how the vaccines could cause autism were proposed by advocates and scientists. One suggestion was that the administration of the measles-mumps-rubella combination vaccine was said to damage the child’s intestinal lining. This, in turn, was said to permit the passage of encephalopathic proteins into the brain.
These proteins, it was proposed, could negatively affect brain development. Another suggestion was that the thimerosal was directly toxic to the child’s nervous system. A third mechanism proposed that the child’s immune system could be overwhelmed by multiple vaccines administered simultaneously. This damage to the immune system would somehow allow harm to the brain’s normal development.
Scientific attempts were made to document the relationship between vaccination and autism in several study formats
The public outcry and concern prompted scientific attempts to document the relationship between vaccination and autism in several study formats. One study type is termed ecological study. Research for ecological studies was performed in several countries. These studies addressed the question of whether the MMR (measles/mumps/rubella) vaccine causes autism. Researchers employed large databases to compare vaccination rates with the incidence of autism diagnoses at the level of whole populations.
The results showed the causal independence of vaccination and autism. These studies also did not support the appearance of a new, variant form of autism. Another variety of studies undertaken on this topic is termed retrospective observational study. Researchers used national health registries to look for the association of cases of autism with vaccination. The results of at least four such retrospective studies showed no temporal relationship between vaccination and a diagnosis of autism. Finally, researchers have pursued prospective observational studies. In this study design, investigators looked at a cohort of vaccinated children over fifteen years. No causal relationship between vaccination, gastrointestinal problems, and autism was demonstrated (Gerber & Offit, 2009).
Objections to these studies have been voiced
Objections to taking action based on these studies have certainly been voiced. Advocates for those with autism, and their families and allies assert that many of these studies are not truly objective. They contend that this is because they are not fully independent. They point to funding by the very corporate interests that manufacture the vaccines (Gerber & Offit, 2009). Additionally, families of autistic children are passionate about crediting their observations.
As the closest and most interested stewards of their children’s behavior, health, and development, they feel that what they see occurring with their own eyes must have some legitimacy. They also point out that the number of vaccinations routinely administered to children has increased several-fold in just a few decades. As a result of their distrust of the scientific studies, many families have refused vaccination for their kids, opting instead to take a chance on remaining free of the diseases, or, in some cases, exposing them deliberately to the disease to develop immunity. This can take the form of ‘measles parties’, where an infected child plays with uninfected kids to give them the infection and confer future resistance (Healthpost, 2013).
There are alternative explanations for autism’s recent rise
The disorder is so recently understood that that may be gaining wider recognition among parents and medical care providers. It is also possible that the range of behaviors that alert parents or practitioners to the possible presence of autism is widening, as the public understands it better (Gerber & Offit, 2009). Additionally, kids are now under increasing pressure to conform behaviourally from earlier ages.
Many kids are in organized institutional settings from early toddlerhood onwards. They are expected to acquire and display social skills in all these venues. Furthermore, schools, under increasing pressure to do more with fewer staff. Under such circumstances, any sort of behavior that deviates from the norm can create crowd control problems. Any disruptive behavior may be flagged for some sort of diagnosis and removal from the mainstream classroom. Finally, it is known that there is some genetic component to autism. There may be entirely different triggers for the expression of a genetic tendency for this disorder that science has not yet identified.
This disorder has been so recently identified that it remains a disturbing mystery. This is cold comfort to the families struggling to live with autism and desperately casting about for some cause for their suffering. Its symptoms and signs are still poorly understood. Obtaining a definitive diagnosis can be difficult, because not every medical practitioner is equally qualified to identify cases reliably. Thus, the number of cases in a population is subject to potential disagreement.
Furthermore, the etiology of this disorder remains obscure. It has genetic bases that have not been thoroughly investigated. Large studies over the long term are needed to conclusively demonstrate or disprove the connection between autism and vaccination. Current scientific evidence does not support a clear connection between vaccines and autism, but a careful parent will want to remain informed of ongoing research. Support for such research should be a priority for the medical establishment.
Gerber, J., & Offit, P. (2009). Vaccines and Autism: A Tale of Shifting Hypotheses. Clinic Infectious Disease, 48(6), 456–461. Web.
Healthpost. (2013). Chicken Pox Parties. Web.
Kanner, L. (1943). Autistic disturbances of affective contact. Nervous Child, 2, 217-250. Web.