Re: Vaccinations (Study shows vaccine-autism link unlikely)

January 31, 2008

Study shows vaccine-autism link unlikely

Infants are shown to rapidly metabolize the type of mercury used in

the preservative thimerosal, still widely used in vaccines around the

world.

By H. Maugh II, Los Angeles Times Staff Writer

January 31, 2008 http://latimes.com

New studies in infants show that the mercury used as a preservative

in vaccines is cleared from the body at least 10 times faster than

researchers had previously believed, a finding that casts further

doubt on the theory that the preservative causes autism.

Researchers had believed that the ethyl mercury in the preservative

thimerosal is metabolized in much the same way as the methyl mercury

found in fish and other sources.

But the first study of ethyl mercury in children shows that levels of

mercury in the blood are only a tenth as high as expected, and the

toxic element is cleared out rapidly, according to a paper to be

published Monday in the journal Pediatrics.

There is a " clear relationship " between the amount of mercury that

must be in the blood, the length of time it must remain there, and

the likelihood of it accumulating in the brain to cause damage, said

Dr. E. Pichichero of the University of Rochester in New York,

the paper's lead author. " Now it's obvious that ethyl mercury's short

half-life prevents toxic buildup from occurring. It's just gone too

fast. "

The bottom line, said Dr. Schaffner of Vanderbilt University,

who was not involved in the study, is that " this is yet another study

added to the increasing stack of studies that are reassuring about

thimerosal's safety. "

But Isaac Pessah of the UC MIND Institute pointed out that the

researchers had only studied healthy children. They didn't

address " the key issue of whether a subset of kids with metabolic

disorders would handle it differently. "

Like the authors, he also noted that they couldn't examine the brain

and other organs for mercury accumulation.

Still, the findings should reassure parents of millions of infants

around the world who receive vaccines with thimerosal even though it

was eliminated from most childhood vaccines in the U.S. in 1999,

Pichichero said. Removing thimerosal would raise prices and limit

availability in poor countries.

Autism strikes as many as one in 167 children born in the U.S. Many

parents link the increase in cases to past use of thimerosal in

vaccines. The new study was designed to address those concerns.

It confirms previous findings of Pichichero and his colleagues in

studies in rhesus monkeys and in a much smaller group of infants.

In the latest study, they examined 72 newborns, 72 2-month-old

infants and 72 6-month-olds at R. Gutierrez Children's Hospital in

Buenos Aires, where thimerosal is still used in vaccinations.

They found that blood mercury levels spiked shortly after

vaccination -- although they remained much lower than levels of

methyl mercury observed in other studies -- then dropped, with a half-

life of 3.7 days. The half-life of methyl mercury, in contrast, is 44

days.

They also found that levels of mercury in the blood were about the

same at birth, at 2 months and at 6 months.

" That's super-reassuring evidence that you don't accumulate mercury,

you get rid of it, " Schaffner said.

The researchers found no evidence of mercury in urine, indicating

that the toxic metal was not coming into contact with the kidneys.

Most of the mercury, they found, was eliminated through the feces.

Dr. Hotez of the Sabin Vaccine Institute, who was not involved

in the study, characterized it as " beating a dead horse. "

" On the other hand, it is useful to know that ethyl mercury does not

have the same metabolism as methyl mercury, " he said.

The study was funded by the National Institutes of Health. The

researchers said they had in the past been paid for consulting with

vaccine manufacturers.