6. Comparison of blood and brain mercury levels in infant monkeys exposed to methylmercury or vaccines containing thimerosal. (2005)

Goes number 6; Taylor number 6

Burbacher TM, Shen DD, Liberato N, Grant KS, Cernichiari E, Clarkson T, Comparison of blood and brain mercury levels in infant monkeys exposed to methylmercury or vaccines containing thimerosal. Environ Health Perspect. 2005 Aug;113(8):1015-21. http://www.ncbi.nlm.nih.gov/pubmed/16079072

Pediatrician "Bartholomew Cubbins":

There has been a number of people touting this paper yet only a few have really read it. Here's the paper in pictures. In short, only about half of the real experiment was done. I can't speculate why the authors stopped short, but I can say that their decision renders this paper almost worthless.

Science Researcher NotMercury, writing at Autism Street:

In an earlier study, Burbacher describes the effects of high dose mercury toxicity and specific changes within the very types of brain cells studied by the Vargas group. He reports an increase in the number of microglial cells and a steady decline in the numbers of astrocytes. These findings are completely inconsistent with data from both Vargas et al. and Rezaie et al. studies. Number of microglia does not reflect state of activation.

In fact, Burbacher reported no ill health effects to monkeys when injected with thimerosal at 1990s levels. A figure, by the way, that would have little bearing on children born after 1999. Burbacher must have recognized the difficulty in obtaining thimerosal-containing vaccines when he did this study, since he chose to add thimerosal to vaccines that were never designed to contain thimerosal. Conditions may have allowed for premature dealkylation and generation of inorganic mercury species prior to injection.

....While it’s true that it would have been accurate to describe thimerosal as 50% mercury by weight, molecular weight is probably meaningless in terms of toxicity (which is determined by the biological effects of a chemical compound on a given organism). While the work of Burbacher does provide insight into the rates at which different forms of mercury are removed from a primate’s brain and bloodstream. As far as proof of toxicity, or specifics of mercury actually causing autism go, conclusions based on this research, seem about a solid as a paper cup.

From a later article, again by NotMercury and Do'C

The sole conclusion to be drawn from Burbacher, 2005 is, and we quote:

“The results indicate that methylmercury is not a suitable reference for risk assessment from exposure to thimerosal-derived Hg.”

Which, when applied to Burbacher, 1996, renders any conclusions drawn from this study as irrelevant. Setting that aside for the moment, the Burbacher, 1996 study used more than 5 times the concentration of mercury before changes in brain cells were observed and those changes looked very different from those reported by Vargas, et al.

So assuming that chronic exposure to methylmercury, not thimerosal, does result in an accumulation of inorganic mercury, Burbacher, 2005 shows a steady decline in the inorganic mercury fraction which never achieves levels required to induce changes in neuroglial populations that may, or may not, be associated with autism in some individuals.

So. Does this paper "demonstrate that vaccines can cause autism"? No. The double weight of flaws in the study design and the the slender conclusions of the paper do not support the vaccine-causation hypothesis.