<a href="http://www.sciencebasedmedicine.org/?p=14" rel="nofollow">http://www.sciencebasedmedicine.org/?p=14</a><p>"Regarding the question of vaccines and autism, for ethical reasons we cannot do a double-blind, randomized, control trial of vaccines with and without thimerosal. However, we can do the next best thing, and, indeed, we now have several good studies since 1999 that do just that. Some of these studies are epidemiological; some are ecological. What allows us to use them to reject the hypothesis that mercury in vaccines is an etiological agent that is either associated with or causes autism is a very simple but powerful prediction that the hypothesis makes. Quite simply, if the hypothesis is true and thimerosal-containing vaccines (TCVs) cause autism (or are even merely a significant contributing factor), we would expect that the removal of thimerosal from vaccines would lead to a rapid decrease in autism incidence and prevalence within 2-5 years.<p>"There have now been several studies that examined this very hypothesis in countries that removed thimerosal from their vaccines before the U.S. did. For example Hviid et al3 reported that autism prevalence in Denmark increased from 1991 to 1996 despite the removal of thimerosal from vaccines, while Madsen et al4 looked at the time period from 1971 to 2000 and concluded that autism diagnoses continued to increase after thimerosal was removed from vaccines. Neither study supported a causal link between TCVs and autism, and they were a prominent part of the dataset that was used by the Institute of Medicine to conclude in 2004 that there was no good evidence to support a link between TCVs and autism. A more recent study by Eric Fombonne5 in Montreal examined 27,749 children born from 1987 to 1998 attending 55 different schools. Cumulative thimerosal exposure by age 2 years was calculated for the 1987-1998 birth cohorts. This exposure ranged from 100-125 μg from 1987 to 1991, 200-225 μg from 1992 to 1995, and then none after 1996, which was when thimerosal was completely removed from vaccines in Canada. The result was that autism, ASD, and pervasive developmental disorder diagnoses continued to increase in all periods, demonstrating no relationship between TCVs and autism or ASDs. Even more recently, a large study6 failed to support a relationship between thimerosal and adverse neurodevelopmental outcomes, a result that led one of the investigators in the study, Sallie Bernard, a proponent of the thimerosal hypothesis, to disavow the study in a case of sour grapes, because it did not show what she had hoped that it would show."