“Do vaccines cause autism?” – This question has drawn a lot of attention, and almost everyone has been waiting for the correct answer to it. The link between autism and vaccines has become a controversial topic, with mainstream scientists and government on one side, whereas many advocacy groups at the other side. Many parents are confused and scared about the health of their children.
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As said by the advocacy groups, thimerosal, which is a preservative added in vaccines, is harmful to central nervous system, and is accountable for the rising rate of ASD among kids in the U.S and in the world. Most of the scientists say that no valid scientific evidence is there to prove that vaccines cause ASD.
In the last 15 years, several recognized medical institutions have examined the evidence from U.S and abroad. The conclusion given by all of them is that no link is there between thimerosal exposure and autism. Moreover, most of the childhood vaccines in U.S no longer have the preservative thimerosal in them, as it has been removed from them.
However, some health activists are continuously challenging the existing science’s validity, and stating that the U.S government is covering up the truth related to autism and thimerosal, by conspiring with vaccine manufacturers.
For over 70 years, thimerosal has been utilized as a preservative for inhibiting fungi and bacteria growth in vaccines. Several vaccines are most efficiently stored in big multi-dose vials, and from these vials, individual doses are drawn by health workers. This leaves the vaccine susceptible to contamination each time a new syringe punctures the rubber top. In the 1920s, several incidents occurred because of the adverse effects of contaminated vaccines, which encouraged vaccine manufacturers to start adding preservatives to vaccines stored in multi-dose vials.
Since, now most vaccines in U.S don’t have thimerosal any longer, the storage of vaccines is done in pre-filled syringes or individual dose vials, which is a more costly system for vaccine manufacturers.
Thimerosal consists of a mercury compound called ethyl mercury. This compound is not identical to methyl mercury, which is contained in high amounts in certain fish. Methyl mercury is accumulated in human tissue, and at specific levels, can cause impairment of cognitive development in small kids. That is why the FDA now states that kids should not take certain fish.
From vaccine studies, scientists state that ethyl mercury doesn’t cause the same adverse effects as that caused by methyl mercury. Additionally, research done by “National Institute of Allergy and Infectious Diseases” says that ethyl mercury is eliminated by the body faster than methyl mercury, so, ethyl mercury is not accumulated in human tissue. Research shows that only known adverse effects of thimerosal exposure while vaccination are minor reactions like swelling and redness at the site of injection in some patients.
Evidence Showing Thimerosal IS Associated with Autism:
Some studies were done in late 1990s to show that autism was triggered by thimerosal. Mark Geier, M.D., conducted studies along with his son David. Mark Geier is a geneticist and former researcher in the “National Institutes of Health”.
As stated by Geiers, kids getting exposure to thimerosal in vaccines, have six times more likelihood of having autism compared to unexposed children. Their conclusions are based on analysis of data acquired from VAERS (Vaccine Adverse Event Reporting System), a reporting system of U.S government, which compiles health complaints related to vaccines.
As a critique of the findings of Geiers, the AAP outlined the issue with depending on VAERS data, saying – the system acquires complaints, but doesn’t have any means to evaluate their legitimacy. The AAP experts argue that Geiers didn’t say how their data was generated, which prevented the accurate evaluation of their methods and attainment of the outcomes. Geiers’ work was found as filled with methodological errors by the “Institute of Medicine”, and the results were dismissed as “uninterpretable” by it.
Evidence Showing Thimerosal is NOT Associated with Autism:
Some of the most significant reports are given below:
- A study was published in the “American Journal of Preventative Medicine” in its August 2003 issue, which looked at autism rates in Sweden and Denmark, where use of thimerosal in vaccines was stopped in 1992. The autism rates from 1987 to 1999 showed an upward trend. If there is a link, the number of autism cases would have been reduced after thimerosal discontinuation.
- In 2003, researchers of U.S CDC (Centers for Disease Control and Prevention), evaluated the data from Vaccine Safety Datalink, which is a database where 8 HMOs log the vaccine records of their patients, along with any adverse reactions. The records of over 120,000 children in 2 different HMOs were analyzed by the authors. The authors didn’t find any difference in rates of autism among kids exposed to various thimerosal levels.
- The Institute of Medicine, in 2004, examined the research on this issue, along with five major studies examining health records of a large number of children in Sweden, Denmark, Britain and U.S., and also the Geiers’ studies. It said as a conclusion that “the body of epidemiological evidence favors rejection of a causal relationship between thimerosal-containing vaccines and autism.”
Besides these, there are several other evidences showing there is no link between thimerosal and autism. Although there are a number of evidences showing there is no link, the debate on the topic continues. The scientific community favors vaccines, but it also wishes to continue doing research to find unknown side effects of vaccines.