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H1N1 (swine) influenza vaccine



This vaccine protects people against swine flu.

Alternative Names

Vaccine - influenza - H1N1; Immunization - influenza - H1N1; Vaccine - influenza - swine flu; Immunization - influenza - swine flu; Swine flu shot; Swine flu vaccine


The H1N1 virus (swine flu) is a new flu virus strain that is causing illnesses in humans worldwide. Symptoms include fever of 100 °F or more and a sore throat or a cough. Chills, sore muscles, and headache may also be present.

The largest number of H1N1 flu cases have occurred in people ages 5 - 24. Fewer cases, and almost no deaths, have been reported in people older than age 64, which is a different pattern from the normal seasonal flu.

See article on H1N1 (swine) flu for more information.

A new H1N1 vaccine is expected to be available in the fall of 2009. Check with your doctor or nurse, local pharmacist, or local health department to see when the vaccine will be available.

There will be two types of swine flu vaccine. One is given as a shot, the other is a nasal spray.

  • The swine flu shot contains killed (inactive) viruses. It is not possible to get the flu from this type of vaccine. The flu shot is approved for people age 6 months and older.
  • A nasal spray swine flu vaccine uses a live, weakened virus instead of a dead one, like the flu shot. It is approved for healthy people ages 2 - 49. It shout NOT be used in those who have asthma or in children under age 5 who have repeated wheezing episodes.


According to the U.S. Centers for Disease Control and Prevention (CDC), these high-risk groups should receive the vaccine as soon as it is available:

  • Pregnant women
  • People who live with or care for children younger than 6 months of age
  • Health care and emergency services personnel
  • People between the ages of 6 months and 24 years of age
  • People from ages 25 through 64 years who are at higher risk for complications from an H1N1 infection

It is possible there will not be enough H1N1 vaccine at first. If this happens, the CDC recommends that these groups receive the vaccination first:

  • Pregnant women
  • People who live with or care for children younger than 6 months of age
  • Health care and emergency services personnel who have direct contact with patients or with infectious substances
  • Children 6 months through 4 years of age
  • Children ages 5 - 18 who are at greater risk for complications of influenza

However, anyone who wants to reduce their risk of the flu should get a flu vaccine. Even if you have had a flu-like illness already, you should still get the swine flu vaccine.

Anyone who receives this new swine flu vaccine still should also get the seasonal flu vaccine that is released every year. You may receive both vaccines on the same day if they are both given as shots. The two nasal spray vaccines (regular flu and swine flu) should be given about a month apart.

Older children and adults will likely need only a single swine flu shot. However, children under age 9 may need a second shot 3 weeks after the first shot.


Most people are protected from the swine flu about 2 weeks after receiving the vaccine.


It is not possible to get the flu from either the injection or shot flu vaccine. However, some people do get a low-grade fever for a day or two after the shot. The flu shot is approved for people age 6 months and older.

The side effects of the swine flu vaccine will probably be very similar to the side effects of the seasonal flu vaccine. Most people have no side effects from the flu shot. Some people have soreness at the injection site or minor aches and low-grade fever for several days.

Normal side effects of the nasal flu vaccine include fever, headache, runny nose, vomiting, and some wheezing. Although these symptoms sound like symptoms of the flu, the side effects do not become a sever or life-threatening flu infection.

The regular seasonal flu shot has been shown to be safe for pregnant women and their babies. Since the new swine flu vaccine is being made using the same process as the regular flu shot, the vaccine is safe for pregnant women, according to the CDC.

As is the case with any drug or vaccine, there is a rare possibility of allergic reaction. Unlike the swine flu vaccine used in 1976, flu vaccines in recent years have shown no association with Guillain-Barre syndrome (GBS) in children, and an extremely small increase in the risk of GBS in adults. The CDC does not expect cases of GBS to occur in people who receive the swine flu shot, but will monitor for increased cases.

Talk to your doctor before receiving the swine flu vaccine if you:

  • Had a severe allergic reaction to chickens or egg protein
  • Have a fever or illness that is more than "just a cold"
  • Had a moderate-to-severe reaction after a previous flu vaccine

Centers for Disease Control and Prevention. 2009 H1N1 influenza vaccine and pregnant women. September 18, 2009. Acessed September 22, 2009.

Centers for Disease Control and Prevention. Use of iInfluenza A (H1N1) 2009 monovalent vaccine recommendations of the advisory committee on immunization practices (ACIP). National Center for Immunization and Respiratory Diseases, CDC, MMWR. August 21, 2009: 58(Early Release);1-8 Acessed September 22, 2009.

Related Taxonomy

Review Date: 9/24/2009
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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