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What
is the flu shot?
The flu shot is an inactivated vaccine (containing
killed virus) that is given with a needle, usually
in the arm. It contains three influenza viruses.
The three vaccine strains – one A (H3N2) virus,
one A (H1N1) virus, and one B virus – are
representative of the influenza vaccine strains
recommended for that year. Viruses for the flu
shot are grown in eggs.
Who
should get a flu shot?
People at high risk for complications of the
flu and people in close contact with them
(including household members) should get a flu
shot.
Who
should not get a flu shot?
Talk with a doctor before getting a flu shot
if you:
1) Have ever had a severe allergic reaction to
eggs or to a previous flu shot
or
2) Have a history of Guillain-Barré
syndrome (GBS).
If you are sick with a fever when
you go to get your flu shot, you should talk to
your doctor or nurse about getting your shot at a
later date. However, you can get a flu shot at the
same time you have a respiratory illness without
fever or if you have another mild illness.
How
effective is the flu shot?
With the flu shot, when the "match"
between vaccine and circulating strains is close,
the vaccine prevents influenza in about 70%-90% of
healthy persons younger than age 65 years. Among
elderly persons living outside chronic-care
facilities (such as nursing homes) and those
persons with long-term (chronic) medical
conditions, the flu shot is 30%-70% effective in
preventing hospitalization for pneumonia and
influenza. Among elderly nursing home residents,
the flu shot is most effective in preventing
severe illness, secondary complications, and
deaths related to the flu. In this population, the
shot can be 50%-60% effective in preventing
hospitalization or pneumonia and 80% effective in
preventing death from the flu.
What
are the risks from getting a flu shot?
The viruses in the flu shot are killed
(inactivated), so you cannot get the flu from a
flu shot. The risk of a flu shot causing serious
harm, or death, is extremely small. However, a
vaccine, like any medicine, may rarely cause
serious problems, such as severe allergic
reactions. Almost all people who get influenza
vaccine have no serious problems from it.
What
are the side effects that could occur?
If these problems occur, they
begin soon after the shot and usually last one to
two days.
Can
severe problems occur?
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Life-threatening allergic
reactions are very rare. Signs of serious
allergic reaction can include breathing
problems, hoarseness or wheezing, hives,
paleness, weakness, a fast heartbeat, or
dizziness. If they do occur, it is within a
few minutes to a few hours after the shot.
These reactions are more likely to occur among
persons with a severe allergy to eggs, because
the viruses used in the influenza vaccine are
grown in hens’ eggs. People who have had a
severe reaction to eggs or to a flu shot in
the past should not get a flu shot before
seeing a physician.
-
Guillain-Barré
syndrome: Normally, about one person per
100,000 people per year will develop
Guillain-Barré syndrome (GBS), an illness
characterized by fever, nerve damage, and
muscle weakness. In 1976, vaccination with the
swine flu vaccine was associated with getting
GBS. Several studies have been done to
evaluate if other flu vaccines since 1976 were
associated with GBS. Only one of the studies
showed an association. That study suggested
that one person out of 1 million vaccinated
persons may be at risk of GBS associated with
the vaccine.
More facts about potential side
effects of the influenza vaccine can be found in
"Prevention
and Control of Influenza, Recommendations of the
Advisory Committee on Immunization Practices
(ACIP)."
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