Vaccines autism

Thimerosal is a preservative used in vaccines that has been purported to cause autism in children. The assumption is that thimerosal, also known as ethyl mercury, causes similar effects as methyl mercury, which has neurotoxic and nephrotoxic... 

A 2004 report by the Institute of Medicine s Immunization Safety Review Committee concluded that available evidence favored rejection of a causal relation between thimerosal-containing vaccines and autism. In like manner, a recent retrospective cohort study conducted by the CDC did not support a causal association between early prenatal or postnatal exposure to mercury from thimerosal-containing vaccines and neuropsychological functioning later in childhood. 

In the 15 years since these criteria were promulgated by declaration, it will be evident that most vaccines are still administered parenterally with the exception of polio and typhoid vaccines. In many ways this can be attributed to the physicochemical characteristics of vaccine antigens themselves, which are large molecules susceptible to proteolytic degradation, denaturation, and rapid clearance from plasma. Some combination vaccines are available which reduce the number of injections. However, the MMR (measles, mumps, and rubella) combination vaccine has gained an unsafe image in the popular press, mainly due to a reputed link with autism in some children that as yet remains unproven scientifically. In some quarters the autism was associated with the use of thiomersalate as a mercurial preservative in multidose injections but, again, this supposition remains unproven. 

Combination vaccines are more convenient in use and are exploited in the familiar DPT and MMR vaccines. However, there is always the possibility of autoimmune reactions and an increased risk of side effects. As noted, these issues have been obscured legally by claims that autism in children is caused by such combinations or the use of thiomersalate as a mercurial preservative. Scientifically it is probably safe to say that these side effects have not been demonstrated convincingly but these issues have caused difficulties for the manufacturers. 

Autism is a poorly understood neurodevelopmental-disease spectrum with a heart-breaking personal story behind every case. But parents of such children have not been served well by these latest claims made well beyond the publically [sic] available evidence. A congressional hearing, like a press conference, is no place to make controversial scientific assessments. And if scientists question the safety of vaccines without making their... 

Two studies suggested a link between measles/MMR immunization and autism. Fudenberg reported that 15 of 40 patients with infantile autism developed symptoms within a week after MMR immunization (487). Wakefield and colleagues evaluated 12 children with chronic enterocolitis and regressive developmental disorders (470). The onset of behavioral symptoms was associated with MMR immunization in eight cases, as reported by the parents. Both reports were non-comparative and anecdotal. By chance alone some cases of autism will occur shortly after immunization, and most children in developed countries receive their first measles or MMR vaccination in the second year of life, when autism typically manifests. The imprecision of the interval between immunization and the onset of behavioral symptoms in the study by Wakefield and colleagues made these data suspect, even before their retraction. 

Data from an earlier study have been reanalysed to test the hypothesis that MMR vaccine might cause autism but that the induction interval needs to be short (495). Evidence for an increased incidence was sought using the case-series method. The study used data on all... 

MMR vaccines, including booster doses. The results of this study, combined with results obtained earlier by the same authors, provided powerful evidence against the hypothesis that MMR vaccine causes autism at any time after immunization. 

Black D, Prempeh H, Baxter T. Autism, inflammatory bowel disease, and MMR vaccine. Lancet 1998 351(9106) 905-6. 

Immunization Safety Review Committee. Immunization safety review measles-mumps-rubella vaccine and autism. In Stratton K, Gable A, Shetty P, McCormick M, editors. Institute of MedicineNational Academy of Sciences, 2001 241. 

Department of Health, England and Wales. MMR vaccine is not linked to Crohn s disease or autism conclusion of an expert scientific seminar. London Press release 98/109, 24 March 1998. 

Farrington CP, Miller E, Taylor B. MMR and autism further evidence against a causal association. Vaccine 2001 19(27) 3632-5. 

Hviid A, Stellfeld M, Wohfahrts J, Melbye M. Association between thiomersal-containing vaccine and autism. J Am Med Assoc 2003 13 1763-6. 

A review of the data generated in the last 4 years has amply described the continued efforts of the scientific community to monitor and understand true measles vaccine-associated adverse events (6). The rapidity and clarity of this same community s debunking of the spurious associations with Crohn s disease and autism suggests that those charged with vaccination programs have learned from past mistakes. 

A conference of the American Academy of Pediatrics on new challenges in childhood immunizations was convened in Oak Brook, IL, on 12-13 June 2000 and reviewed data on what is known about the pathogenesis, epidemiology, and genetics of autism and the available data on hypothesized associations with Crohn s disease, measles, and MMR vaccine. The participants concluded that the available evidence did not support the hypothesis that MMR vaccine causes either Crohn s disease or autism or associated disorders. They recommended continued scientific efforts directed to the identification of the causes of autism (69). 

Peltola H, Pat] a A, Leinikki P, Valle M, Davidkin 1, Paunio M. No evidence for measles, mumps, and rubella vaccine-associated inflammatory bowel disease or autism in a 14-year prospective study. Lancet 1998 351(9112) 1327-8. 

Caiman K. Measles, measles-mumps-rubella (MMR) vaccine, Crohn s disease and autism. Dear doctor letter from the Chief Medical Officer, March 1998, PL/CMO/98/2. 

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