This
message is to inform you of the release
of a new book entitled "'Evidence
of Harm, Mercury in Vaccines and the
Autism Epidemic: A Medical Controversy,"
authored by David Kirby, a journalist
and freelance writer. The book is a “look
back” at issues related to thimerosal
and vaccines – and is primarily
written from the perspective of people
who believe there is an association between
vaccines and autism. Mr. Kirby is on
a media tour to promote the book, a schedule
of which can be found at www.evidenceofharm.com.
Autism
spectrum disorders (ASDs) are an urgent
public health issue, and affect the lives
of too many families. Parents and families
who have children affected by ASD are
understandably interested in finding
the causes of this lifelong disability.
We appreciate the concern of parents
of children with autism and their desire
for information about its cause and treatment.
We are dedicated to understanding better
the biological, environmental, and gene-environmental
causes of autism and other developmental
disabilities. There is much that remains
unknown about autism. However, we do
know that early identification and intervention
can help improve children’s outcomes.
CDC continues to support research related
to autism, including studies designed
to examine the possible causal association
between autism and other possible environmental
causes, including thimerosal-containing
vaccines.
We
at CDC are in the process of reviewing
Mr. Kirby’s book in detail, but
the general issues raised in the book
have already been extensively examined,
including by the Institute of Medicine
(IOM), in the past few years. As the
IOM concluded in a recent report, the
vast majority of studies, which have
involved hundreds of thousands of children
in a number of countries, have failed
to find any association between exposure
to thimerosal in vaccines and autism;
that is, they have failed to find any
evidence of harm.
CDC
places a high priority on vaccine safety
and the integrity and credibility of
its vaccine safety research. We welcome
attention and interest on vaccine safety.
The public should expect safe vaccines,
and the public is entitled to safe vaccines.
CDC is committed to monitoring and ensuring
vaccine safety. We carefully evaluate
allegations of harmful vaccine effects
and are prepared to adjust our policies
if allegations prove scientifically valid.
Given
the historical nature of the book, it
is important to emphasize that today,
with the exception of some influenza
(flu) vaccines, none of the vaccines
used in the U.S. to protect preschool
children against 12 infectious diseases
contain thimerosal as a preservative.
Though some flu vaccines contain thimerosal
as a preservative, preservative free,
reduced thimerosal-content influenza
vaccines are also available for use in
infants, with the supply expected to
increase significantly for the coming
next season.
CDC
and a number of agencies within the Department
of Health and Human Services (HHS) have
responded to concerns related to the
use of thimerosal as a preservative in
some of the recommended childhood vaccines.
All supported, as a proactive and precautionary
measure, efforts to remove, as quickly
as possible, the use of thimerosal as
a preservative in childhood vaccines.
CDC and the National Institutes of Health
(NIH) have funded studies to assess the
health effects of thimerosal as well
as assess whether there is an association
between thimerosal and autism, learning
or developmental disabilities, and other
adverse health outcomes. Research in
these areas is ongoing. CDC and the Food
and Drug Administration (FDA) have encouraged
vaccine manufacturers in their efforts
to remove thimerosal as a preservative
as fast as possible, and FDA has facilitated
the review and licensing of thimerosal
preservative-free vaccines.
To
assist you in addressing questions generated
by the release of “Evidence of
Harm”, we want to remind you of
these resources and provide you with
additional talking points:
Stephen
L. Cochi, M.D., M.P.H.
Acting
Director, National Immunization Program
Centers
for Disease Control and Prevention
Talking
Points on VSD Screening Analysis
The VSD screening analysis
published in Pediatrics in November 2003
found no consistent statistically significant
associations between exposure to vaccines
that contained thimerosal as a preservative
and a wide range of neurodevelopmental
problems, including autism and, attention
deficit disorder (ADD).
SafeMinds and the book
“Evidence of Harm” by David
Kirby have highlighted 5 “generations”
of analyses in the VSD screening analysis.
They have implied that the initial analysis
which found increased relative risks
for certain categories of exposure for
autism, ADD, and sleep disorders was
correct and subsequent iterations of
analyses were undertaken in order to
minimize or conceal a true relationship
between thimerosal and autism.
There are three major
reasons why the final published report
differed from the initial November-December
1999 analysis.
First, in early analyses
there were errors both in the dataset
and in the analysis. The dataset used
in the initial analyses contained a number
of errors in thimerosal content of vaccines.
These errors were identified and corrected.
Managed Care Organizations (MCOs) that
did not have outpatient data available
were initially included by mistake; this
error was subsequently corrected, as
were various errors in programming, including
double counting of cases.
Second, there was little
variation in thimerosal content of vaccines
used in the participating VSD managed
care organizations. Differences in thimerosal
exposure among children in the study
were mostly due to the fact that some
children were vaccinated “on time”
and others were not, rather than due
to differences in receipt of thimerosal-free
vs thimerosal-containing vaccines. Managed
care organizations make every effort
to vaccinate the children for whom they
provide care on time with recommended
childhood vaccines. Children who do not
receive recommended childhood vaccines
are likely not receiving the same level
or intensity of medical care within the
managed care organization than children
who are vaccinated – and if a child
is not being seen in the MCO clinics
for vaccinations, the child is also unlikely
to have autism or other diagnoses entered
into managed care databases. This variation
in the utilization of managed care services
was a difficult issue to address; however
researchers were able to do so by including
statistical adjustments for health care
utilization in the final published analyses.
Third, the final paper
includes additional years of follow up,
with many more children included who
had been diagnosed with autism. Critics
have suggested that follow up was extended
in order to “dilute” the
study with addition of younger children
who are less likely to be diagnosed with
autism. This is not true. The published
analyses account for age by comparing
children in a given age group with one
level of thimerosal exposure with children
in that same age group with a different
level of thimerosal exposure. Because
this statistical method was used, the
addition of younger children does not
dilute the study’s ability to identify
an association if one existed, and in
fact the study is substantially strengthened
by continuing follow up into older age
groups where the diagnosis of autism
is more likely to be made.
The allegation that subsequent
iterations of the VSD analysis were undertaken
in order to minimize or conceal a true
relationship between thimerosal and autism
is false. The integrity of CDC’s
vaccine safety research and its reputation
for excellence are among the most valued
assets of our agency. This commitment
not only stems from our scientific and
medical dedication, it is also personal
-- for most of us who work at CDC are
also parents and grandparents. And as
such, we too, have high levels of personal
interest and concern in the health and
safety of children, families, and communities.
The
Centers for Disease Control and Prevention’s
Immunization Works Monthly Update is
provided to national health care provider
and consumer groups for distribution
to their members and constituencies.
The immunization information provided
is non-proprietary and is encouraged
to be widely disseminated and shared. |
