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Issue No. 003/09 |
20
November 2009
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Main Topic:
H1N1 FLU
(SWINEFLU)
VACCINE
SAFETY
General
Questions and Answers on Guillain-Barré syndrome (GBS)
September 14,
2009, 11:00 PM ET
What is Guillain-Barré
syndrome (GBS)?
Guillain-Barré syndrome (GBS) is a rare disorder in which a person's own
immune system damages the nerve cells, causing muscle weakness and sometimes
paralysis. GBS can cause symptoms that last for a few weeks or several
months. Most people recover fully from GBS, but some people have permanent
nerve damage. In rare cases, people have died of GBS, usually from difficulty
with breathing. In the United States, for example, an estimated 3,000
to 6,000 people develop GBS each year on average, whether or not they
received a vaccination. This is about 1 to 2 cases of GBS per 100,000
people.
What causes
GBS?
Scientists do not fully understand what causes GBS, but it is believed
that stimulation of the body's immune system may play a role in its development.
Here's what scientists know for sure: About two-thirds of people who develop
GBS symptoms do so several days or weeks after they have been sick with
a diarrheal or respiratory illness. Infection with the bacterium Campylobacter
jejuni is one of the most common risk factors for GBS. People can also
develop GBS after having the flu or other infections (such as cytomegalovirus
and Epstein Barr virus). On very rare occasions, they may develop GBS
in the days or weeks following receiving a vaccination.
Who is at
risk for developing GBS?
Anyone can develop GBS, but it is more common among adults than children.
The incidence of GBS increases with age, and people over age 50 are at
greatest risk for developing GBS. Each year, on average, about 3,000 to
6,000 people in the United States develop GBS whether or not they received
a vaccination - that's 1 to 2 people out of every 100,000 people.
Do vaccines
cause GBS?
It is not fully understood why some people develop GBS, but it is believed
that the nerve cells are damaged by a person's own immune system. Many
types of infections, and in very rare cases vaccines, may activate the
immune system to cause damage to the nerve cells.
How common
is GBS, and how common is it after people are vaccinated for seasonal
influenza?
GBS is rare. Each year, about 3,000 to 6,000 people in the United States
develop GBS whether or not they received a vaccination - that's 1 to 2
people out of every 100,000 people. This is referred to as the background
rate.
In 1976, there
was a small risk of GBS following influenza (swine flu) vaccination (approximately
1 additional case per 100,000 people who received the swine flu vaccine).
That number of GBS cases was slightly higher than the background rate
for GBS. Since then, numerous studies have been done to evaluate if other
flu vaccines were associated with GBS. In most studies, no association
was found, but two studies suggested that approximately 1 additional person
out of 1 million vaccinated people may be at risk for GBS associated with
the seasonal influenza vaccine. It is important to keep in mind that severe
illness and possible death can be associated with influenza, and vaccination
is the best way to prevent influenza infection and its complications.
What happened
in 1976 with GBS and the swine flu vaccine?
Scientists first reported a suspected link between GBS and vaccinations
in 1976, during a national campaign to vaccinate people against a swine
flu virus. The investigation found that vaccine recipients had a higher
risk for GBS than those who were not vaccinated (about 1 additional case
occurred per 100,000 people vaccinated). Given this association, and the
fact that the swine flu disease was limited, the vaccination program was
stopped. Since then, numerous studies have been done to evaluate if other
flu vaccines were associated with GBS. In most studies, no association
was found, but two studies suggested that approximately 1 additional person
out of 1 million vaccinated people may be at risk for GBS associated with
the seasonal influenza vaccine.
Why did some
people develop GBS after they received the 1976 swine flu vaccine?
The Institute of Medicine (IOM) conducted a thorough scientific review
in 2003 and concluded that people who received the 1976 swine influenza
vaccine had a slight increased risk for developing GBS. Scientists have
multiple theories on why this increased risk may have occurred, but the
exact reason for this association remains unknown.
Do you expect
that the 2009 H1N1 vaccine will be associated with GBS?
We expect the 2009 H1N1 vaccine to have a similar safety profile as seasonal
flu vaccines, which have very good safety track records. The seasonal
influenza vaccine has not been consistently associated with GBS.
How will public
health authorities investigate cases of GBS?
Ensuring the safety of vaccines is a high priority for CDC. CDC and its
partners have an aggressive plan to actively monitor the 2009 H1N1 vaccine
to ensure its safety. Several systems are in place to monitor vaccine
safety. One of these systems is the Vaccine Adverse Event Reporting System
(VAERS).
CDC and FDA co-manage
VAERS, which serves as an early warning system to collect voluntary reports
about possible side effects that people experience following vaccinations.
CDC and FDA scientists review all VAERS reports and store the information
in a computerized database that is monitored to detect new, unusual, or
rare health events that could be possible side effects of vaccines.
In addition to
the normal vaccine safety monitoring systems, CDC is proactively putting
additional monitoring systems in place to ensure safety after licensing.
Some of these systems include: actively observing persons in defined geographic
areas, collaborating with professional organizations for reports of any
adverse events after vaccination, and conducting thorough investigations
when severe adverse events occur to determine whether they may have been
associated with the vaccine. Through these numerous approaches, we will
be able to detect any possible risk of GBS that might be associated with
the 2009 H1N1 vaccine early in the vaccination campaign and take appropriate
action.
How will the
federal government determine whether people who receive the 2009 H1N1
vaccine have an increased risk for GBS?
GBS cases occur every year in the general population for many different
reasons. To monitor whether people who receive the 2009 H1N1 vaccine have
an increased risk for GBS, U.S. public health officials will determine
if the number of GBS cases reported among people who receive the 2009
H1N1 vaccine is higher than the number of cases reported in the general
population.
If there is an
increase in the number of reported cases, public health officials will
conduct intensive investigations. If any problems are detected with this
2009 H1N1 vaccine, they will be reported to health officials, healthcare
providers, and the public, and health officials will take needed action
to ensure the public's health and safety.
" Links to non-federal
organizations are provided solely as a service to our users. These links
do not constitute an endorsement of these organizations or their programs
by CDC or the federal government, and none should be inferred. CDC is
not responsible for the content of the individual organization Web pages
found at these links.
  Centers
for Disease Control and Prevention 1600 Clifton Rd. Atlanta, GA 30333,
USA 800-CDC-INFO (800-232-4636) TTY: (888) 232-6348, 24 Hours/Every Day
- cdcinfo@cdc.gov
| IOMS
Newsletter - 20 November 2009 |
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Issue
No. 003/09
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