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:''This article uses the International Nonproprietary Name "thiomersal", not the common U.S. spelling "thimerosal". The thiomersal controversy describes claims that vaccines containing the mercury-based preservative thiomersal contribute to the development of autism and other brain development disorders. The current scientific consensus is that no convincing scientific evidence supports these claims,〔 and a 2011 journal article described the vaccine-autism connection as "the most damaging medical hoax of the last 100 years".〔 Thiomersal is an organomercury compound used as a preservative in vaccines since the 1930s to prevent bacterial and fungal contamination. Following a mandated review of mercury-containing food and drugs in 1999, the Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) asked vaccine makers to remove thiomersal from vaccines as quickly as possible as a purely precautionary measure, and it was rapidly phased out of most U.S. and European vaccines.〔 It is still used in all multi-dose vials of flu vaccines in the U.S.〔http://www.cdc.gov/flu/protect/vaccine/thimerosal.htm〕〔http://www.cdc.gov/flu/protect/vaccine/vaccines.htm〕 In the context of perceived increased autism rates and increased number of vaccines in the childhood vaccination schedule, some parents believed the action to remove thiomersal was an indication that the preservative caused autism.〔 The potential impact of thiomersal on autism has been investigated extensively. Multiple lines of scientific evidence have shown that thiomersal does not cause autism. For example, the clinical symptoms of mercury poisoning differ significantly from those of autism. In addition, multiple population studies have found no association between thiomersal and autism, and rates of autism have continued to increase despite removal of thiomersal from vaccines.〔 Thus, major scientific and medical bodies such as the Institute of Medicine and World Health Organization (WHO) as well as governmental agencies such as the Food and Drug Administration〔 (FDA) and the CDC reject any role for thiomersal in autism or other neurodevelopmental disorders. In spite of the consensus of the scientific community, some parents and advocacy groups continue to contend that thiomersal is linked to autism.〔 This controversy has caused harm due to parents attempting to treat their autistic children with unproven and possibly dangerous treatments, discouraging parents from vaccinating their children due to fears about thiomersal toxicity〔 and diverting resources away from research into more promising areas for the cause of autism.〔 Thousands of lawsuits have been filed in the U.S. to seek damages from alleged toxicity from vaccines, including those purportedly caused by thiomersal.〔 US courts have ruled against multiple representative test cases involving thiomersal,〔 suggesting the majority are unlikely to succeed.〔 Outside of the United States, worries about thiomersal had not gained any significant traction as of 2009. ==History== Thiomersal was introduced as a preservative in the 1930s to prevent the growth of infectious organisms such as bacteria and fungi, and has been in use in vaccines and other products such as immunoglobulin preparations and ophthalmic and nasal solutions. Vaccine manufacturers have used preservatives to prevent microbial growth during the manufacturing process or when packaged as "multi-dose" products to allow for multiple punctures of the same vial to dispense multiple vaccinations with less fear of contamination.〔 After the FDA Modernization Act of 1997 mandated a review and risk assessment of all mercury-containing food and drugs, vaccine manufacturers responded to FDA requests made in December 1998 and April 1999 to provide detailed information about the thiomersal content of their preparations. A review of the data showed that while the vaccine schedule for infants did not exceed FDA, Agency for Toxic Substances and Disease Registry (ATSDR), or WHO guidelines on mercury exposure, it could have exceeded Environmental Protection Agency (EPA) standards for the first six months of life, depending on the vaccine formulation and the weight of the infant.〔 The review also highlighted difficulty interpreting toxicity of the ethylmercury in thiomersal because guidelines for mercury toxicity were based primarily on studies of methylmercury, a different mercury compound with different toxicologic properties. Multiple meetings were scheduled among various government officials and scientists from multiple agencies to discuss the appropriate response to this evidence. There was a wide range of opinions on the urgency and significance of the safety of thiomersal, with some toxicologists suggesting there was no clear evidence that thiomersal was harmful and other participants like Neal Halsey, director of the Institute of Vaccine Safety at Johns Hopkins School of Public Health, strongly advocating removal of thiomersal from vaccines due to possible safety risks. In the process of forming the response to this information, the participants attempted to strike a balance between acknowledging possible harm from thiomersal and the risks involved if childhood vaccinations were delayed or stopped. Upon conclusion of their review, the FDA, in conjunction with the other members of the US Public Health Service (USPHS), the National Institutes of Health (NIH), CDC and Health Resources and Services Administration (HRSA), in a joint statement with the AAP in July 1999 concluded that there was "no evidence of harm caused by doses of thimerosal found in vaccines, except for local hypersensitivity reactions."〔 Despite the lack of convincing evidence of toxicity of thiomersal when used as a vaccine preservative, the USPHS and AAP determined that thiomersal should be removed from vaccines as a purely precautionary measure.〔 This action was based on the precautionary principle, which assumes that there is no harm in exercising caution even if it later turns out to be unnecessary. The CDC and AAP reasoned that despite the lack of evidence of significant harm in the use of thiomersal in vaccines, the removal of this preservative would increase the public confidence in the safety of vaccines.〔 Although thiomersal was largely removed from routine infant vaccines by summer 2001 in the U.S., some vaccines continue to contain non-trace amounts of thiomersal, mainly in multi-dose vaccines targeted against influenza and tetanus. In 2004 Quackwatch posted an article saying that chelation therapy has been falsely promoted as effective against autism, and that practitioners falsified diagnoses of metal poisoning to "trick" parents into having their children undergo the process. , between 2–8% of children with autism had had the therapy. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Thiomersal controversy」の詳細全文を読む スポンサード リンク
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