Influenza vaccine


An influenza vaccine protects you against the flu. A new form of the flu vaccine needs to be made most years to protect you against the exact strains that are expected to be most common.

Alternative Names

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


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 weakened immune system.

2012-2013 VACCINE

The flu vaccine that will be given this fall and winter will also protect you against H1N1 (swine) flu. You do not need a  separate vaccine.

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

Flu vaccines are generally given at the beginning of the "flu season" -- usually around October 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.


The Centers for Disease Control and Prevention (CDC) recommend 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. The CDC recommends extra efforts to vaccinate the following people:

Older children and adults only need a single flu shot each year. However, children under age 9 should get two shots 1 month apart unless they have received two vaccinations for seasonal influenza since July 1, 2010. Be sure to ask your child’s doctor for more specific information.


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


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.

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.


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:

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


Centers for Disease Control and Prevention (CDC). Prevention and Control ofI nfluenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices (ACIP), 2012. MMWR. 2012 Aug 17;61(32):613-618.

Review Date: 11/5/2012
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 A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.
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