The pioneer works on autism spectrum disorders in Africa had been by Longe and Asuni (Longe & Asuni, 1972) and Lotter (Lotter, 1978; Lotter, 1980) about three decades after the first report of autism spectrum disorder by Kanner in 1943 (Kanner, 1943). Longe (1976) and Lotter (1978) reported ASD among African Children in African continent, covering countries such as Ghana, Nigeria, Kenya, Zimbabwe, and Zambia & South Africa. In 1970s, the prevalence of ASD in Africa was about 0.7% among children with Intellectual Disability (ID) (Lotter, 1978).
Until about two and half decades ago, autism spectrum disorder was thought to be exclusively an illness peculiar to Western civilization. The existing evidence then suggested that autism occurs mostly in countries with high technological development, high level of industrialization and with salience of nuclear family system. However autism spectrum disorder was also believed to be relatively uncommon even in Western Europe and North America at that time. Nevertheless, the idea that autism may not exist in Africa was further supported by very infrequent report of cases on the continent and other parts of the world outside the West.
Autism rates in developing countries have risen remarkably in the past 20 years. For children born in 1992, according to the U.S. CDC, about 1 in 150 would be diagnosed with an autism spectrum disorder (ASD). For children born in 2004, about 1 in 68 children would receive an ASD diagnosis. It is difficult to compare autism rates from the 1990s and later with rates from the 1940s through the 1980s: in earlier years, autism was associated primarily with very severely affected individuals and the rate of autism was estimated to be only about 1 in 10,000 people. Beginning in the 1990s, our understanding of the spectrum of autism has expanded greatly, and now individuals who would most likely previously not have been thought of as having autism may be classified with one of a variety of ASDs.
Although child vaccination rates remain high, some parental concern persists that vaccines might cause autism. Three specific hypotheses have been proposed: (1) the combination measles-mumps-rubella vaccine causes autism by damaging the intestinal lining, which allows the entrance of encephalopathic proteins; (2) thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system; and (3) the simultaneous administration of multiple vaccines overwhelms or weakens the immune system. All three are discussed below;
#1 – MMR Vaccines cause autism;
The widespread fear that vaccines increase risk of autism originated with a 1997 study published by Andrew Wakefield, a British surgeon. The article was published in The Lancet, a prestigious medical journal, suggesting that the measles, mumps, rubella (MMR) vaccine was increasing autism in British children.The paper has since been completely discredited due to serious procedural errors, undisclosed financial conflicts of interest, and ethical violations. Andrew Wakefield lost his medical license and the paper was retracted from The Lancet. Nonetheless, the hypothesis was taken seriously, and several other major studies were conducted. None of them found a link between any vaccine and the likelihood of developing autism.
#2 – Thimerosal, an ethylmercury-containing preservative in some vaccines, is toxic to the central nervous system;
Thimerosal is a vaccine preservative comprised of ethyl mercury. It has been used in vaccines since the late 1930s. When the volume of vaccines given to children in the U.S. grew dramatically in the early 1990s, so did the amount of thimerosal a child received. At its peak, children would receive thimerosal as high as 125x the EPA safe level.
The autism epidemic has mirrored the increase in thimerosal in shots, so they are correlated. However, it is not known whether too many vaccines, too much mercury, or both may be responsible for the growth in autism cases. Therefore, studies of thimerosal in vaccines may be based on a false premise that a vaccine free of mercury is “safe” — vaccines have many other toxic ingredients (like aluminum) and thimerosal-free vaccines generate adverse events, too. As one example, the MMR vaccine has never contained thimerosal, but has many known adverse events.
Despite the biological implausibility of the contention that thimerosal in vaccines caused autism, 7 studies—again descriptive or observational—were performed. Four other studies have been reviewed in detail elsewhere but are not discussed here because their methodology is incomplete and unclear and, thus, cause difficulty in drawing meaningful conclusions.
#3 – Multiple vaccines overwhelms or weakens the immune system;
When studies of MMR vaccine and thimerosal-containing vaccines failed to show an association with autism, alternative theories emerged. The most prominent theory suggests that the simultaneous administration of multiple vaccines overwhelms or weakens the immune system and creates an interaction with the nervous system that triggers autism in a susceptible host.
Fears over the safety of vaccines are understandable. The CDC vaccination schedule calls for children to receive up to 14 inoculations by the age of six – many of them vaccines developed within the last twenty years. Many parents distrust these vaccines; worried about the potential for risks and long-term side effects. Research, however, shows that most of our biggest fears about vaccinations are unfounded.
Infant immune systems are stronger than you might think. Based on the number of antibodies present in the blood, a baby would theoretically have the ability to respond to around 10,000 vaccines at one time. Even if all 14 scheduled vaccines were given at once, it would only use up slightly more than 0.1% of a baby’s immune capacity. And scientists believe this capacity is purely theoretical. The immune system could never truly be overwhelmed because the cells in the system are constantly being replenished. In reality, babies are exposed to countless bacteria and viruses every day, and immunizations are negligible in comparison.
Though there are more vaccinations than ever before, today’s vaccines are far more efficient. Small children are actually exposed to fewer immunologic components overall than children in past decades.
Conclusion
Twenty epidemiologic studies have shown that neither thimerosal nor MMR vaccine causes autism. These studies have been performed in several countries by many different investigators who have employed a multitude of epidemiologic and statistical methods. The large size of the studied populations has afforded a level of statistical power sufficient to detect even rare associations. These studies, in concert with the biological implausibility that vaccines overwhelm a child’s immune system, have effectively dismissed the notion that vaccines cause autism. Further studies on the cause or causes of autism should focus on more-promising leads.
References:
https://www.fourteenstudies.org/studies_thimerosal.html
http://pediatrics.aappublications.org/content/111/3/674
https://academic.oup.com/…/Vaccines-and-Autism-A-Tale-of-Sh…
http://www.publichealth.org/…/under…/vaccine-myths-debunked/
http://cdn.intechopen.com/pdfs/20038.pdf
