Autism-Vaccine Link: Evidence Doesn't Dispel Doubts
Many major medical groups say vaccines don't cause autism. Many parents say they do. So who's right?
Vaccine-Autism Disconnect: The Mercury Question
As if the MMR vaccine wasn't enough of a hot potato, other vaccines also
When researchers started looking for a possible link between autism and the
MMR, all other childhood vaccines came under scrutiny, too. In 1998, 30
different vaccines with thimerosal in them were given to children. U.S. public
health officials realized that the recommended schedule of vaccines could give
some children mercury that exceeded the limit considered safe by government
In 1999, the U.S. Public Health Service and the AAP asked vaccine makers to
reduce or remove thimerosal in vaccines. By 2001, all routine childhood
vaccines were available thimerosal-free.
The 2004 IOM review included five large-scale studies that compared autism
rates in vaccinated and unvaccinated children. These and other recent studies,
including one published in TheNew England Journal of Medicine in
September 2007, have shown that children who received vaccines with thimerosal
are not more likely to have been diagnosed with autism than those that weren't
vaccinated or received less thimerosal from vaccines.
Sallie Bernard, founder of the advocacy group Safe Minds, tells WebMD that
she doesn't believe the results of epidemiological studies showing no link
between autism and vaccines. "We say you have to look at the biology,"
In her opinion, mercury poisoning and autism seem too much alike to rule out
mercury as a cause. Mercury poisoning can cause brain damage, and symptoms can
be similar to those of autism.
"I certainly wouldn't argue that the only source of mercury and the only
source of harm is the mercury in vaccines," Bernard says. She says she
believes children continue to be harmed by vaccines that still contain
But while Harvard's McCormick agrees that mercury is a dangerous substance,
the claim that mercury poisoning and autism are the same doesn't hold up under
scrutiny, she says. "It's based on a very superficial similarity."
Symptoms of mercury poisoning can
include irritability, depression, anxiety, visual problems, speech problems,
and sensory nerve problems. In autism, there can be findings of delayed speech,
increase or decrease in response to sensory stimuli, and avoidance of human eye