Information

The flu is a contagious respiratory disease caused by an influenza virus. Thousands of people in the U.S. die each year from the flu or its complications. Most of those who die are the elderly, young children, or people with compromised immune systems. For more information about flu symptoms and treatment, see: Flu

2011-2012 VACCINE

The flu vaccine that will be given during the fall and winter of 2011 - 2012 will also protect you against swine (H1N1) flu. There is no separate vaccine for swine flu.

There are two types of flu vaccines: a flu shot and a nasal spray vaccine.

• The flu shot contains killed (inactive) viruses, so it is not possible to get the flu from this type of 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.
• There is also a high-dose version of the flu shot approved for people 65 and older. However it is not known if the higher dose vaccine is better at protecting from influenza illness.
• A nasal spray flu vaccine called FluMist uses a live, weakened virus instead of a dead one like the flu shot. It is approved for healthy people aged 2 to 49 who are not pregnant. It should not be used in those who have asthma or children under age 5 who have repeated wheezing episodes.

Flu vaccines are generally given at the beginning of the "flu season" -- usually late October or early November in the U.S. However, they may be given as late as March, and still provide some benefit.

People traveling to other countries should be aware that the flu may occur at different times of the year from the U.S.

WHO SHOULD GET THE VACCINE

The Centers for Disease Control and Prevention (CDC) recommends that everyone 6 months and older should receive the flu vaccine. Some people are more likely to get the flu or to have a severe infection if they catch it. People at risk for more serious flu infections should always get a flu vaccine every year. Thus, the CDC recommends extra efforts to vaccinate people in the following groups:

• Pregnant women or women who will be pregnant due flu season
• Children younger than 5 years and especially those under 2 years (but 6 months or older)
• Household contacts and caregivers of children under the age of 6 months, including breastfeeding women
• Are a health care worker or live with a health care worker
• Have chronic lung or heart disease
• Have sickle cell anemia or other hemoglobinopathies
• Live in a nursing home or extended care facilities
• Live with people who have chronic health problems
• Have kidney disease, anemia, severe asthma, diabetes, or chronic liver disease
• Have a weakened immune system (including those with cancer or HIV/AIDS)
• Receive long-term treatment with steroids for any condition

Older children and adults only require a single shot each year. However, children under age 9 need two shots 1 month apart the first time they receive flu vaccine or if they have not previously received two doses during one flu season.

BENEFITS

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

RISKS AND SIDE EFFECTS

Most people have no side effects from the flu shot. Soreness at the injection site or minor aches and low grade fever may be present for several days.

As is the case with any drug or vaccine, there is a rare possibility of allergic reaction.

The regular seasonal flu shot has been shown to be safe for pregnant women and their babies. Most people have no side effects from the flu shot. Soreness at the injection site or minor aches and low grade fever may be present for several days.

Normal side effects of the nasal spray 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 severe or life-threatening flu infection.

WHO SHOULD NOT RECEIVE A FLU VACCINE

Some people should not be vaccinated without first talking to their doctor. The vaccine is not approved for people under 6 months of age. In general, you should not get a flu shot 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
• Developed Guillain-Barre syndrome within 6 weeks after receiving a flu vaccine

If you meet any of the above criteria, ask your doctor if a flu vaccine is safe for you.

Alternative Names

Vaccine - influenza; Immunization - influenza; Flu shot; Flu vaccine

References

Centers for Disease Control and Prevention (CDC). Prevention and Control ofI nfluenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2011. MMWR. 2011 Aug 26;60:1128-32.

Updated: 4/16/2012

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.