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Vaccine
Additive Linked to Autism
Douglas Fischer, RedOrbit News, November 3, 2005
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A mercury-laced
preservative once widely added to pediatric vaccines exposes
infants' brains to twice the neurotoxin previously suspected,
offering evidence that health guidelines may underestimate the
risk newborns face, researchers say in a report being published
today. The additive, thimerosal, has been used in vaccines since
the 1930s and is almost 50 percent mercury by weight. Since
2001, manufacturers have gradually phased it out of almost all
domestic pediatric vaccines, though it remains in use overseas
in cheaper "multidose" vaccines.
The study, being published today in Environmental Health
Perspectives, a peer-reviewed publication of the National
Institutes of Health, also chides health officials for
abandoning an earlier recommendation that the preservative be
completely phased out and further studies conducted.
And it fuels the debate over the federal government's aggressive
vaccination plan that subjects infants to a battery of shots
some of which contain aluminum and other potentially harmful
compounds in their first weeks of life.
"We're talking about a low-level delivery of a toxin given to a
baby on the first day of its life," said mercury expert Boyd
Haley, chairman of the chemistry department at the University of
Kentucky, who was not involved in the study.
"What's needed is a total study of the sensibility of the
vaccine program. Why would you want to vaccinate a baby on the
first day of its life?"
The report is one of the first to look beyond mercury blood
levels resulting from vaccines. Instead it examines both the
amount and type of mercury reaching the brain. It suggests
health officials examined the wrong compound and failed to look
far enough when assessing the danger of mercury in thimerosal.
This is largely a past concern for the United States, given the
predominance today of thimerosal-free vaccines. Both the study's
lead author and the Centers for Disease Control and Prevention
on Wednesday urged parents to have their children vaccinated.
"That's the first message," said Thomas Burbacher, lead author
and associate professor in the Department of Environmental and
Occupational Health Sciences at the University of Washington's
School of Public Health.
"The bottom line is that trying to assess the effects of
acompound with very little or no data is not a good thing to do.
... Unfortunately, we started doing studies on this compound way
too late. Basic information like this should've been available
decades ago."
The problem is very much alive for developing nations, however,
where the additive is common. The World Health Organization has
expressed interest in Burbacher's research.
The problem, Burbacher said, is that regulators trying to assess
thimerosal's harm used as a benchmark methylmercury, a widely
studied compound, rather than the little-known compound called
ethylmercury in thimerosal. Both compounds cross the blood-
brain barrier. But methylmercury breaks down slowly, whereas
ethylmercury dissipates fairly rapidly, suggesting to regulators
that a standard based on methylmercury would adequately protect
infants. Burbacher and colleagues found ethylmercury's fast
breakdown leaves higher levels of so-called "inorganic" mercury
in the brain. Inorganic mercury lingers in the brain for a year
or more, potentially altering certain cells. A previous study
has shown such damaged cells are also found in children with
autism. Using monkeys, Burbacher found the brains of
thimerosal-exposed infants had twice as much inorganic mercury
as methylmercury- exposed infants. The Food and Drug
Administration has never required testing of thimerosal's safety
or of its safe exposure levels for newborns and children.
Although high mercury levels particularly as a result of
vaccinations have long been suspected as a leading cause of
skyrocketing autism levels, the CDC and Burbacher cautioned
Wednesday against drawing any conclusion linking the two. "To
date, the vast majority of the science doesn't support an
association between thimerosal and incidences of autism," said
CDC spokesman Glen Nowak. But "at the end of the day, we still
don't know what causes autism." Others, however, expect such
links to become apparent as thimerosal fades from use in the
United States. Already, noted Haley, California's autism rates
have decreased three of the past four quarters a first. "There's
something in the vaccines doing it. That something is
thimerosal."
The FDA's Web site on thimerosal and vaccinations, including a
chart showing common pediatric vaccines and the date thimerosal
was eliminated, can be found at
http://www.fda.gov/cber/vaccine/thimerosal.htm.
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