The flu shot contains a killed form of several types of flu viruses. The vaccine causes your immune system to make antibodies. Then, if you are exposed to the flu later, the antibodies can attack and destroy the virus.

It takes about 2 weeks for your body to make the antibodies. So it's best to get the flu vaccine as soon as it's available. But the vaccine can still help if you get it during the flu season.

There are different ways to get a flu vaccine. Ask your doctor what is right for you.

Flu viruses change quickly, so each year scientists make a new vaccine. To have the best chance of being protected, you need to get a flu vaccine every year. You can't get the flu from a flu vaccine.

It is recommended that adults ages 65 and older get a high-dose flu shot.^{footnote 2}

The CDC recommends that everyone age 6 months or older should get a flu vaccine each year.

A flu vaccine is especially important for people who are at high risk for getting other health problems from the flu. This includes:

• People who are age 50 or older.
• People who have long-term (chronic) diseases, such as heart disease, diabetes, kidney disease, and lung disease, including asthma.
• People who live in nursing homes or long-term care centers.
• People who have a weak immune system.
• People who are pregnant.
• Young children.

The flu vaccine is also important for people who could spread the flu to others who are at high risk. This includes:

• Anyone who lives with or cares for young children.
• Anyone in close contact with a person who is at high risk for other health problems from the flu. This includes family, friends, and caregivers.
• Health care workers.

Children younger than 6 months of age and people with severe, life-threatening allergies to the flu vaccine or any part of the vaccine should not get a flu vaccine.

Talk to your doctor before getting a flu vaccine if you:

• Have a severe allergy to eggs or any part of the vaccine.
• Have had a serious reaction to the flu vaccine in the past.
• Have had Guillain-Barré syndrome.
• Are sick. If you are ill and have a fever, wait until you're better before you get a flu vaccine.

People who can't get a flu vaccine but are at risk from the flu may be able to take an antiviral medicine instead.

The flu vaccine may keep you from getting the seasonal flu. This can save you time (fewer days missed from work or school) and money (fewer doctor visits, medicines, and hospital costs). The flu vaccine can also help prevent the spread of the flu to others. If you are pregnant, it can help prevent your newborn baby from getting the flu.^{footnote 1}

If you do get the flu, your symptoms may be milder and you may be less likely to have other health problems from the flu.

The flu shot may cause mild problems, such as soreness, redness, and swelling on the arm where you got the shot. You might also have a fever and muscle aches for a day or two after you get the vaccine.

The flu vaccine can't cause the flu.

The risk of a serious problem from the flu vaccine (such as a bad allergic reaction) is very small.