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News
Institute of Medicine (IOM) Report
Hepatitis B Vaccine and Demyelinating Neurological Disorders
(Released May 30, 2002)
Questions and
Answers
-
Why was the report done?
-
How does the committee examine a hypothesis?
- What vaccine safety concern did the IOM committee examine?
-
What
were the committee’s conclusions regarding hepatitis B
vaccine and demyelinating neurological disorders?
-
What recommendations did the committee make regarding policy,
research and communications?
- Why was the report done?
Public
confidence in immunization programs is essential to our nation’s health.
In recent years, increasing public attention has focused on issues regarding
vaccine safety. Vaccine safety concerns may decrease public acceptance of
immunizations and result in resurgence of vaccine preventable diseases.
Issues involving the safety of vaccines, particularly childhood vaccines,
may concern certain members of the public, health care professionals, the
public health community, the media, Congress, vaccine manufacturers, and
federal agencies.
In
response to these concerns, the Centers for Disease Control and Prevention
(CDC) and the National Institutes of Health (NIH) have asked the National
Academy of Sciences, Institute of Medicine (IOM) to establish an independent
expert committee to review hypotheses about existing and emerging
immunization safety concerns. These reviews include an assessment of factors
such as the biologic mechanisms of the hypothesis, competing alternative
hypotheses, as well as the available scientific evidence to date.
This
is the fourth report completed by the IOM committee. The first report,
released in April 2001, examined the hypothesized link between Measles,
Mumps, and Rubella (MMR) vaccine and autism; this was followed by a second
report in October 2001 concerning the hypothesis that thimerosal-containing
vaccines may cause neurodevelopmental disorders. The committee’s third
report, released in February 2002, examined the concern that multiple
immunizations might cause immune dysfunction. Information about these reports can be obtained at the following Web
sites:
 Top
- How
does the committee examine a hypothesis?
For
each hypothesis to be examined, the committee assesses both the scientific
evidence and the issue’s social significance in a broader societal
context. The scientific assessment has two parts:
-
An examination of evidence of any biological mechanisms relevant to the
hypothesis (these are classified as theoretical only, weak, moderate,
or strong) and
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An examination of the evidence regarding a possible causal relation
between the vaccine and the adverse event.
The
significance assessment considers the nature of the health risks
associated with the vaccine-preventable disease and with the adverse event
in question and the level of public concern about the safety issue. The
findings of the scientific and significance assessments provide the basis
for the committee’s recommendations.
The
Immunization Safety Review Committee is composed of 15 members with
expertise in pediatrics, neurology, immunology, internal medicine,
infectious diseases, genetics, epidemiology, biostatistics, risk perception
and communications, decision analysis, public health, nursing, and ethics.
The committee members were selected on the basis of strict criteria to
eliminate any potential or perceived conflict of interest.
Top
- What
vaccine safety concern did the IOM committee examine?
For
this review, the committee addressed the suggestion that hepatitis B vaccine
can cause certain neurological disorders, called “demyelinating
disorders,” such as multiple sclerosis and Guillain-Barré syndrome.
Multiple sclerosis (MS) is a disease of the central nervous system
that involves the destruction of the myelin sheath that surrounds neurons,
resulting in the formation of "plaques." Because they involve the
destruction of the myelin sheath that covers nerve tissue, diseases such as
MS are known as "demyelinating" diseases.
Guillain-Barré syndrome (GBS) also results from a loss of
myelin.
The disorder causes temporary loss of body movement and sensation,
usually starting at in the lower parts of the body and moving upwards.
Most people who experience GBS recover within 6 to 9 months.
Certain vaccines, such as influenza (flu) vaccine, have been linked
to an increased risk for GBS.
Other demyelinating neurological disorders
considered in the committee’s review include optic neuritis, acute
disseminated encephalomyelitis (ADEM), transverse myelitis, and brachial
neuritis.
Top
- What
were the committee’s conclusions regarding hepatitis B vaccine and
demyelinating neurological disorders?
The
committee concluded that the scientific evidence favors rejection of a
causal relationship between hepatitis B vaccination in adults and MS.
However, the committee felt that there was not enough evidence to
accept or reject a causal relationship between the hepatitis B vaccine and
other specified demyelinating conditions.
The committee also concluded that there is only weak evidence for
biological mechanisms by which hepatitis B vaccination could possibly cause
demyelinating neurological disorders.
Top
- What
recommendations did the committee make regarding policy, research and
communications?
The
committee did not recommend a policy review by any of the national and
federal vaccine advisory bodies on the basis of concerns about
demyelinating neurological disorders. The committee recommended a number of research activities including
continued monitoring of side effects experienced by hepatitis B vaccine
recipients. In addition, the committee recommended enhanced communication
research and activities by government agencies and professional
organizations.
Top
More Information
 Return
to IOM report on Hepatitis B main page
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