Thimerosal Down but Autism Rising
Removal of Mercury From Child Vaccines Fails to Halt Autism Increase
Jan. 7, 2008 -- Autism rates continue to go up despite removal of
thimerosal, which contains a form of
mercury, from nearly all child vaccines, California data show.
The finding adds to a growing body of
evidence against the "
thimerosal hypothesis." The hypothesis holds that vaccines using
thimerosal as a preservative -- given to
children or their
mothers -- causes autism.
As a precautionary measure, by March 2001 thimerosal was removed (except for
trace amounts) from all recommended infant vaccines. The only childhood
vaccines that still contain more than trace amounts of thimerosal are
multiple-dose vials of some flu vaccines.
An early look at data from California suggested that removal of thimerosal
might have led to a decline in autism. But now an updated look at the data by
the California Department of Public Health shows that there was no such
"We are reassured that we found no link between routine childhood
vaccination and increases in childhood autism in the data," California DPH
Medical Officer Robert Schechter, MD, tells WebMD. "But the finding that
there are increasing numbers of kids who need services is not reassuring. We
support efforts to find preventable causes of autism."
The data are based on children referred to the California Department of
Developmental Services System, a network of regional centers that serve people
disabled by autism, mental retardation, and other developmental
The most recent data come from March 2007, reflecting autism in children as
young as age 3. Data on children younger than 3 are not routinely entered into
the system. One 2001 look at the data by proponents of the thimerosal
hypothesis suggested that there was a decline in autism beginning in 1994. A
year earlier, a thimerosal-free Hib vaccine reduced the amount of thimerosal to
which children were exposed.
But Schechter says there was no such decline.
"Not enough time had passed for autism in the younger children in that
time period to be fully recognized," he says. "We saw with additional
time, rather than going up and going down, autism rates continued to go
Autism Rise: Is It Something in the Environment?
It may still be too soon to draw conclusions from the California data, says
Sally Bernard, co-founder and executive director of SafeMinds, an organization
that advocates "sensible action for ending mercury-induced neurological
"Their conclusions rely on the younger age group of 3- to
5-year-olds," Bernard tells WebMD. "So if you are looking at trends, it
is premature to make such conclusions."
Bernard is far less concerned about what the data do not show than about
what they do show: autism rates are still going up.
"This tells us that because autism is steadily increasing, there is an
environmental source," she says. "You cannot use this data to rule out
thimerosal as a factor. What you can say is there may be -- and probably are --
other environmental triggers that play a role. It is probable that exposure to
these other factors may be increasing."
If thimerosal does play a role in autism, it isn't a big one, says Gary W.
Goldstein, MD, president and CEO of Baltimore's Kennedy Krieger Institute.
"The thimerosal is pretty much gone now, and autism rates are still
going up," Goldstein tells WebMD. "It just is not the case that
thimerosal in vaccines is the primary cause for the increase in autism. Could
there be 5% of children more susceptible to autism and the thimerosal just
tipped them over the edge? Yes, but this study did not address that
The Schechter study appears in the January issue of Archives of General