October 7, 2009, 8:00 PM ET
A flu vaccine is the single best way to protect against influenza illness. This season, there is a seasonal flu vaccine to protect against seasonal flu viruses and a 2009 H1N1 vaccine to protect against the 2009 H1N1 influenza virus (sometimes called “swine flu”).
This page contains information about the 2009 H1N1 flu vaccine.
There are two kinds of 2009 H1N1 vaccines being produced:
About 2 weeks after vaccination, antibodies that provide protection against 2009 H1N1 influenza virus infection will develop in the body.
The 2009 H1N1 vaccine will not protect against seasonal influenza viruses.
When to Get Vaccinated
Vaccination against 2009 H1N1 should begin as soon as vaccine is available and
continue throughout the influenza season, into December, January, and beyond.
This is because the timing and duration of flu activity can vary. Flu seasons
can last as late as April or May. By early October 2009, extensive 2009 H1N1 flu
activity was being reported in the United States. It’s possible that there may
be waves of 2009 H1N1 activity during the 2009-2010 flu season that hit
communities more than once over the course of the season. While 2009 H1N1
viruses are likely to be the most common cause of influenza this season, CDC
still expects that seasonal influenza viruses will circulate and continues to
recommend that people get a seasonal flu vaccine to protect against seasonal flu
viruses. The
ACIP has issued separate recommendations on who should get the 2009-10 seasonal
vaccine
Vaccine Supply
The U.S. government has purchased 250 million doses of 2009 H1N1 vaccine, so
anyone who wants to get the vaccine will have the opportunity to do so.
Vaccine will be made available as quickly as possible as it rolls off
the production lines, so initially, the vaccine will be
available in limited quantities.
Who Should Get Vaccinated
CDC’s Advisory Committee on Immunization Practices (ACIP), a panel made up of
medical and public health experts, met July 29, 2009, to make recommendations on
who should receive the 2009 H1N1 vaccine when it becomes available. While the
federal government has purchased enough vaccine so that anyone who wants to get
vaccinated can, ACIP’s statement on the “Use
of Influenza A (H1N1) 2009 Monovalent Vaccine” recommends that vaccination
efforts should focus first on people in five target groups who are at higher
risk for 2009 H1N1 influenza or related complications, are likely to come in
contact with influenza viruses as part of their occupation and could transmit
influenza viruses to others in medical care settings, or are close contacts of
infants younger than 6 months (who are too young to be vaccinated). These five
target groups make up an estimated 159 million people in the United States.
Initial Target Groups Are:
When vaccine is first available, ACIP recommends that programs and providers
administer vaccine to people in the following five target groups (order of
target groups does not indicate priority):
No shortage of 2009 H1N1 vaccine is expected, but vaccine availability and demand can be unpredictable and initially the vaccine may be available in limited quantities. Because the amount of vaccine available at first will be small, the ACIP also made recommendations regarding which people within the groups listed above should be prioritized if the vaccine is initially available in extremely limited quantities. For more information see the ACIP recommendations on the Use of Influenza A (H1N1) 2009 Monovalent Vaccine at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr58e0821a1.htm
Once the demand for vaccine for the target groups has been met at the local level, ACIP recommends that programs and providers begin vaccinating everyone from the ages of 25 through 64 years. Current studies indicate that the risk for infection among persons 65 and older is less than the risk for younger age groups. However, once vaccine demand among younger age groups has been met, ACIP recommends that programs and providers should offer vaccination to people 65 or older.
The ACIP has issued separate recommendations on who should get the 2009-10 seasonal vaccine.
Who Should Not Be Vaccinated
There are some people who should not get any flu vaccine without first
consulting a physician. These include:
Vaccine Effectiveness
The ability of a flu vaccine to protect a person depends on the age and health
status of the person getting the vaccine, and the similarity or "match" between
the viruses or virus in the vaccine and those in circulation. CDC analyzes
circulating inflluenza viruses on an ongoing basis to determine how closely
matched they are to vaccine viruses and publishes the information weekly in
FluView. In addition, every year CDC monitors vaccine effectiveness. For
more information about flu vaccine effectiveness, see
How Well Does the Seasonal Vaccine Work?
Vaccine Side Effects (What to Expect)
The same side effects typically associated with the seasonal flu shot and the
seasonal nasal spray vaccine are expected with the 2009 H1N1 flu shot and 2009
H1N1 nasal spray vaccine.
These are:
The flu shot: The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that could occur are:
If these problems occur, they begin soon after the shot, are usually mild, and usually last 1 to 2 days. Almost all people who receive influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions.
The nasal spray: The viruses in the nasal-spray vaccine are
weakened and do not cause severe symptoms often associated with influenza
illness. (In clinical studies, transmission of vaccine viruses to close contacts
has occurred only rarely.)
In children, side effects from LAIV can include:
In adults, side effects from LAIV can include
For more information about vaccine side effects and safety see General Questions and Answers on 2009 H1N1 Influenza Vaccine Safety.
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