Flu vaccines use killed or weakened forms of flu viruses to stimulate production of antibodies in the body. Once your body makes enough antibodies, it is protected against flu infection.

Flu vaccine gives protection for approximately eight months. More information about the effectiveness of flu vaccine is available on the CDC’s Seasonal Influenza (Flu) webpage.

Flu viruses change from year to year, which means two things:

1. You can get the flu more than once during your lifetime.
2. A vaccine made to protect against flu viruses circulating last year may not protect against the newer viruses. That is why the influenza vaccine is updated to include current viruses every year.

The Centers for Disease Control and Prevention (CDC) recommends an annual flu vaccine for people over the age of 6 months. Flu vaccine is particularly important for people at high risk of serious flu complications:

1. People at high risk for complications from the flu.
   • People 65 years or older, regardless of health status.
   • People living in a nursing home or long-term care facility.
   • People 6 months or older with chronic heart or lung conditions, like asthma.
   • People 6 months or older who has a recent history of metabolic diseases, chronic kidney disease or a weakened immune system.
   • People 6 months to 18 years who is on long-term aspirin therapy. (People in this age group that take aspirin and get sick with the flu are at a risk of developing Reye syndrome.) Visit our Reye syndrome webpage to learn more.
   • Women who will be pregnant during the influenza season and women up to two weeks after delivery..
   • All children under 2 years old.
2. People 50 to 64 years old.
   • Nearly one-third of people 50 to 64 years old in the United States have medical conditions that increase their risk of potentially serious flu complications.
3. People who will be in close contact with someone at high risk for complications from the flu (see above).
   • This includes all health care workers, caregivers of children 6 to 23 months old, and close contacts of people 65 years or older.

Yes. Some people should not get vaccinated.

People who cannot get a flu shot:

• Children younger than 6 months old. .
• People with severe, life-threatening allergies to the vaccine or any of its ingredients.
• People who had a severe reaction to an influenza vaccination in the past.

People who should speak to their doctor or health care provider before getting a flu shot:

• People who have severe allergy to eggs should speak with their health care provider about getting vaccinated. The CDC updated its recommendations for people with egg allergies (chicken eggs are an ingredient used to grow the virus used in the flu vaccine). The CDC recommends that people who have a severe allergy to eggs should be vaccinated in a medical setting and supervised by a health care provider who is able to recognize and manage severe allergic conditions.
• People who have ever had Guillain-Barré syndrome should speak with a health care provider about getting vaccinated. Visit our Guillain-Barré syndrome webpage to learn more.
• People who are currently sick with a fever. (Once the fever goes down, it is okay to get vaccinated).

Side effects for the seasonal flu shot are mild and mostly include soreness or redness at the injection site. Sometimes hoarseness, red eyes, or itchiness occur. Side effects will appear soon after the shot is given and last one or two days.

Severe allergic reactions are very rare, but if they occur it will be a few minutes to a few hours after the shot is administered.

The flu shot does not give you the flu.

A rare side effect is a neurological disorder called Guillain-Barré Syndrome. If you have ever had Guillain-Barré Syndrome you should speak with your health care provider about getting vaccinated.

Severe allergic reactions are very rare, but if they occur it would be a few minutes to just a few hours after the shot was administered. Seek medical attention immediately if you experience shortness of breath, wheezing or hives.