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Flu Shot (Vaccine) for Adults

Medically reviewed by Last updated on Apr 2, 2024.

What is the flu shot?

The flu shot is a vaccine given in your upper arm or thigh to help prevent influenza (the flu). The flu is caused by a virus. The virus spreads through direct contact with someone who has the flu. For example, a person with the virus on his or her hands can spread it by shaking hands with someone. Several types of viruses cause the flu. The viruses change over time, so new vaccines are made each year. The vaccine begins to protect you about 2 weeks after you get it. Get the vaccine as soon as recommended each year, usually starting in September or October.

What should I tell my doctor before I get a flu shot?

Who should not get the flu shot or should wait to get it?

You may need to wait to get the flu shot, or instead get the nasal flu vaccine. Tell your healthcare provider if:

What are the risks of the flu shot?

The vaccine may cause mild symptoms, such as a fever, headache, and muscle aches. You may also have mild to moderate soreness or redness at the area where you were given the shot. You may still get the flu after you receive the vaccine. You may have an allergic reaction to the vaccine. This can be life-threatening.

Treatment options

The following list of medications are related to or used in the treatment of this condition.

Call your local emergency number (911 in the US) if:

When should I seek immediate care?

When should I call my doctor?

Care Agreement

You have the right to help plan your care. Learn about your health condition and how it may be treated. Discuss treatment options with your healthcare providers to decide what care you want to receive. You always have the right to refuse treatment. The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

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Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.