One of the countries where thimerosal has been retained in vaccines is Peru. This situation is a consequence of a controversial decision by the World Health Organization (WHO) and its Latin American partner the Pan American Health Organization (PAHO) to retain thimerosal as a vaccine preservative because of economic considerations. PAHO buys most of its vaccines from the same vaccine manufacturers who sold thimerosal-containing vaccines (TCVs) in the United State. And like the US in the early 1990s, PAHO countries like Peru have recently adopted the Hib and hepatitis B vaccines as part of their recommended childhood immunization programs. Peru also continues to use the thimerosal-containing whole cell DPT vaccine, instead of the safer but more expensive acellular pertussis variety.

The result of these PAHO decisions is that Peruvian children are now exposed to thimerosal in amounts that would be considered in excess of EPA guideline in the U.S. Not surprisingly, some Peruvian scientists have taken issue with this choice and took it upon themselves to investigate the issue. In their words:

“In Peru, the authorities of the Ministry of Health (MINSA) continue using vaccines with high thimerosal content (whose multidose…form is, to date used in some health establishments), noting that it has no side effects. This generated a serious challenge by the public, part of the medical community and a number of non-governmental organizations. This debate requires that begin (sic) to shed light on the investigations and take concrete steps on this issue.”

So these Peruvian researchers published a study, published in the September 2007 edition of the Peruvian medical journal Anales de la Facultad de Medicina but only recently translated into English (for the on-line version of the September 2007 edition, see HERE) in which they examined the effect of thimerosal exposure on infant hamsters. They exposed 45 baby hamsters to three different series of injections, two of which involved no thimerosal exposure and a third that was designed to mimic the weight-adjusted ethyl mercury content of the U.S. childhood immunization program in the 1990s.

The findings were stark. As the three groups of infants matured, the thimerosal-exposed hamsters showed clear signs of developmental injury due to their ethyl mercury exposure, a weight adjusted concentration that added up to less a total dose of less than 1 microgram (an amount many times less than the 187.5 micrograms human infants received). The mercury exposed hamsters showed dramatic developmental differences in terms of body weight, brain weight and heights, with a statistical certainty that there was a toxic effect that exceeded 99.99%.

When the 45 hamsters were sacrificed, the researchers compared the brain tissue of the three groups and again found dramatic differences in the thimerosal-exposed infant hamster brains. Ethyl mercury produced clear injuries in the three types of brain tissue: hippocampus, cerebellum and cerebral cortex. Furthermore, the exposed hamsters showed clear evidence of many different kinds of tissue damage, such as reduced neuron density, increased cell death, impaired myelin development and increased inflammation. These results were also significant with a certainty of greater than 99.99%.

The Peruvian team didn’t mince words. Taking pains to translate their full paper into English (the journal typically publishes English language abstracts, but provides full text only in Spanish), they summarized their findings in unambiguous terms.

“In conclusion, thimerosal exposure, in quantities equivalent to those of human vaccines, reduced the body weight, encephalon weight and height of postnatal hamsters in a significant way; in this way, it produced a lesser development and growth delay. Also, it produced severe neurotoxic effects at encephalon level expressing histopathological alterations at hippocampus, cerebral cortex and cerebellum levels.”

This hamster model doesn’t simply stand alone. Instead it joins a succession of animal studies all of which demonstrate that exposing infant animals to thimerosal produces developmental brain injury. Mady Hornig’s work in mice provided the template for the Peruvian group and their hamster findings provide confirmation for Hornig’s finding of thimerosal toxicity in mice. In her recent presentation at the International Meeting for Autism Research (IMFAR), Laura Hewitson (see the Age of Autism article HERE ) reported on a primate model that showed clear evidence of developmental injury in rhesus macaque monkeys after exposure to thimerosal and a range of vaccine antigens.

We can’t take human infants and cut up their brains. That’s why scientists use animal models to evaluate the effect of potentially dangerous medical treatments and toxic chemicals. In a consistent set of these models, a wide range of researchers from different labs all over the world, researchers are finding that thimerosal causes injury in infant animals. Despite this dramatic and repeated body of evidence, public health authorities—the CDC, the WHO, the PAHO—persist in exposing the developing human brain to ethyl mercury, one of the most toxic chemicals man has ever invented. These officials consider the interests of their programs—the economics of distribution of vaccines in Peru, the yield of flu vaccine production in the U.S. and the continued targeting of pregnant women and infants for flu shots—to carry greater weight than any countervailing evidence. But by now, the evidence is so indisputable that the question has become a question of moral rather than scientific choices. Why do these officials persist in continuing policies and products that harm children?

The Peruvian researchers are clearly calling their PAHO colleagues to account for their decisions. In the final paragraph of their paper the authors write, in somewhat halting English translation:

“While it is true, it is very difficult to extrapolate these findings to other animal experimentation groups and over human beings, our results, as the multiple scientific evidence recently published about thimerosal, clearly indicates the toxic nature of this substance at the same dose and the same chronology as human immunizations; therefore we suggest the employment of alternative preservatives in vaccines, especially those intended to pregnant women, neonates and small children based in the prevention and precaution principles of all medical interventions.”

Sick mice. Sick hamsters. Sick monkeys. Sick children. The evidence is clear and the policies are devastating a generation of children on a global basis. When will this madness stop?

Mark Blaxill is Editor-at-Large for Age of Autism.