Vaccine
Link To Autism Refuted In Defining Report
Institute Of Medicine
Says Findings Conclusive
A US government
panel has concluded decisively that childhood vaccinations do
not cause autism, according to a report issued recently.
Since concerns about
a suspected link were first raised in the late 1990s, many scientific
studies have refuted this association. The latest Institute
of Medicine (IOM) report referred specifically to the measles-mumps-rubella
(MMR) vaccine as well as to vaccines that at one point contained
the mercury-based preservative thimerosal.
Considerable debate
has been conducted for many years as to whether these might
trigger the onset of autism in small children.
Approximately 15 out
of every 10,000 children born are diagnosed with autism. Autism
is more prevalent in boys than girls, with four times as many
boys affected than girls.
Although it is not
clear whether this debate will ever be put completely to rest,
the report is very "close to the final word," says Dr. Tom Saari,
a professor of pediatrics at the University of Wisconsin Medical
School in Madison and a member of the American Academy
of Pediatrics (AAP) committee on infectious diseases.
"It's clearly not
going to settle it for some people, but it clearly suggests
that there are other avenues that are much more profitable to
pursue in terms of trying to understand what autism is and how
to both prevent and treat it," says Dr. Marie C. McCormick,
head of the IOM Immunization Safety
Review Committee and a professor of maternal and child
health at the Harvard School of Public Health.
"The overwhelming
evidence from several well-designed studies indicates that childhood
vaccines are not associated with autism," Dr. McCormick says.
Concerns
Raised a Decade Ago
The controversy regarding
autism and vaccines began in 1998 with the publication of a
case series describing 12 children with pervasive developmental
disorder, eight of whom exhibited behavioral problems their
parents and physicians said coincided with receiving the MMR
vaccine.
This question of timing
is one argument supporters of the vaccine-autism link have used
to further their point of view.
"The timing issue
certainly affects the perception of an association between MMR
and autism, because MMR is given in the second year of life,
which is when symptoms of autism tend to be more evident," Dr.
McCormick says.
Another issue is the
fact that, until 1999, the preservative thimerosal was used
in more than 30 vaccines licensed and marketed in the US.
That year, the US
Food and Drug Administration determined that small children
receiving the standard vaccination schedule might be exposed
to cumulative doses of ethylmercury that exceeded some safety
guidelines. Measures were quickly taken to remove thimerosal
from these vaccines.
The IOM
had already published two reports on possible links between
autism, the MMR vaccine, and thimerosal. Those reports concluded
there was no evidence to support a link between MMR and autism,
but there was not enough evidence to disprove a thimerosal-autism
connection.
In any event, today
vaccines given to infants either have no thimerosal or negligible
amounts.
Thimerosal is still
included in some influenza vaccines but, Dr. Saari says, "The
potential exposure a child would get from a flu vaccine is extremely
small." And there are thimerosal-free versions available this
year, albeit not enough to inoculate everybody.
For the current study,
the committee looked at existing research on the subject, namely
five studies that explored the thimerosal-autism connection
and 14 that looked at MMR and autism. The five thimerosal studies
found no association between that compound and autism, while
the 14 MMR studies also found no credible connection.
"We have 12 well-designed
studies that say it isn't so," Dr. Saari says. "In that particular
arena, I think most of us feel very comfortable with the weight
of the evidence."
However, the committee
determined that five studies found a link between thimerosal
and autism, and another two found a connection between MMR and
the disease.
The panel concluded
the evidence presented was not compelling. "They were not high
enough quality to sway the conclusions of the other reports,"
Dr. McCormick states.
Finally, the committee
also concluded that there was insufficient evidence that activation
of the immune system by the vaccine somehow triggered autism.
Research
Continues on Some Fronts
Some studies will
continue to determine if a link exists between autism and vaccines.
Dr. Timothy Buie,
an instructor of medicine at Harvard Medical School, is in the
middle of a study to see if the measles virus is present in
the colon of children with autism.
"We are trying to
find out if the presence of the virus is any more relevant in
autistic kids," he explains. "We're not sure what we're going
to find."
The original 1998
case studies saw GI symptoms in the children that seemed to
point to a link between autism and the MMR vaccine.
"I'm not certain there
is enough information out there to draw that conclusion [of
the IOM]," Dr. Buie says. "There are still not a lot of centers
actively looking at the question.
"I think they do deserve
a little bit more time and a few more centers to put their two
cents in to see if they can find for or find against," Dr. Buie
says. "Anything that would lead us to more concern or less concern
is of value."
In addition, the Autism
Society of America (ASA) states in a press announcement
that it is "calling on the government to launch biological and
clinical studies that look at the subgroup of individuals with
autism who may be genetically susceptible to the effects of
vaccines and/or thimerosal before putting this issue to rest."
The ASA
states that the IOM should not rely just on
broad, epidemiological studies which look at large numbers of
people and do not determine cause and effect, but should use
the smaller, clinical studies to obtain more specific information.
Always consult your
child's physician for more information. |
July 2004
Vaccine
Link To Autism Refuted In Defining Report
Concerns
Raised a Decade Ago
Research
Continues on Some Fronts
Autistic
Disorder Defined
Online
Resources
Autistic
Disorder Defined
Autistic disorder
(also called autism) is a neurological and developmental disorder
that usually appears during the first three years of life.
A child with autism
appears to live in his/her own world, showing little interest
in others, and a lack of social awareness. The focus of an autistic
child is a consistent routine and includes an interest in repeating
odd and peculiar behaviors.
Autistic children
often have problems in communication, avoid eye contact, and
show limited attachment to others.
Autism can prevent
a child from forming relationships with others (in part, due
to an inability to interpret facial expressions or emotions).
A child with autism
may resist cuddling, play alone, be resistant to change, and/or
have delayed speech development.
Persons with autism
tend to exhibit repeated body movements (such as flapping hands
or rocking) and have unusual attachments to objects. However,
many persons with autism excel consistently on certain mental
tasks (such as counting, measuring, art, music, and memory).
The cause of autism
is not known. Research suggests that autism is a genetic condition.
It is believed that several genes are involved in the development
of autism.
Research studies in
autism have found a variety of abnormalities in the brain structure
and chemicals in the brain, but there have been no
consistent findings.
One theory is the
possibility that autistic disorder is a behavioral syndrome
that includes several distinct conditions. However, parenting
behaviors are not the cause or a contributing factor to the
cause or causes of autism.
For the first time,
standard guidelines have been developed to help identify autism
in children before the age of 24 months.
In the past, diagnosis
of autism was often not made until late preschool-age or later.
The new guidelines can help identify children with autism early,
which means earlier, more effective treatment for the disorder.
The standardized guidelines
were developed with assistance from 11 different organizations
and were published in Neurology, a journal
of the American Academy of Neurology.
According to the guidelines,
all children before the age of 24 months should routinely be
screened for autism and other developmental delays at their
well-child check-ups. Children that show developmental delays
and other behavior disorders should be further tested for autism.
According to the guidelines,
less than 30 percent of children undergo age-appropriate screening
at their well-child check-ups.
By screening children
early for autism, those diagnosed with the disorder can be treated
immediately and aggressively.
Always consult your
child's physician for more information.
Online
Resources
(Our Organization
is not responsible for the content of Internet sites.)
American
Academy of Neurology
American
Academy of Pediatrics
Centers
for Disease Control and Prevention (CDC)
National
Institute of Child Health & Human Development
National
Institute of Mental Health
National
Institutes of Health (NIH)
US
Food and Drug Administration |
