Flu shot: Your best bet for avoiding influenza

Date Updated: 10/23/2026

By Mayo Clinic Staff

Flu, also called influenza, is an infection of the nose, throat and lungs, which are part of the respiratory system. The flu is caused by a virus. Most people with the flu get better on their own. But influenza can cause serious complications for some groups of people.

Getting a seasonal flu vaccine is the best way to prevent the flu and its complications for almost everyone. A vaccine can lower the risk of getting the flu. It also can lower the risk of dying of the flu or having serious illness from the flu and needing to stay in the hospital.

This year's seasonal flu vaccines each provide protection against three influenza viruses that researchers expect to be most common this flu season.

When are flu vaccines available?

Flu vaccines are often available in the U.S. around September. The viruses that cause the flu spread at high levels during certain times of the year in the Northern and Southern hemispheres. These are called flu seasons. In North America, flu season usually runs between October and May.

It takes about six months for pharmaceutical makers to produce most flu vaccine. In the United States, shipments often begin in late summer.

Once you get a flu vaccine, it takes up to two weeks to build immunity. So it's usually best for people in the United States to get a flu vaccine in September or October. But you can benefit from the vaccine even if you don't get it until later in flu season.

Why do I need to get vaccinated every year?

Flu viruses change quickly. Last year's vaccine may not protect you from this year's viruses. New flu vaccines are released every year to keep up with rapidly changing flu viruses.

When you get vaccinated, your immune system makes antibodies to protect you from the viruses included in the vaccine. But antibody levels may decline over time, which is another reason to get a flu shot every year.

Who should get the flu vaccine?

Seasonal flu vaccines are available in the U.S. for people age 6 months and older. Mayo Clinic recommends a seasonal flu vaccine for anyone who doesn't have a medical reason to avoid the vaccine.

Getting a flu vaccine lowers:

The risk of getting the flu. If the vaccine is given later in pregnancy, the flu vaccine helps protect a newborn from the flu too.
The risk of having serious illness from the flu and needing to stay in the hospital due to the flu.
The risk of dying of the flu.

High-risk groups include:

People age 65 and older.
People in nursing homes or long-term care.
Young children, especially those 2 years old and younger.
People who are pregnant, who are more likely to develop influenza complications, particularly in the second and third trimesters.

In the United States, some groups have a higher risk of needing treatment in the hospital for flu. Those groups include people who are Native American or Alaska Native, Black, or Latino.

Other groups at high risk of flu complications include people with:

Weakened immune systems.
A body mass index (BMI) of 40 or higher.
Conditions that affect the nervous system or how the brain processes information.

People with certain medical conditions have a higher risk of flu complications, including:

People who have chronic illnesses, such as asthma, heart disease, kidney disease, liver disease and diabetes.
People who have had a stroke.
People who are younger than 20 years of age and are receiving long-term aspirin therapy.

Are certain flu vaccines recommended based on age or immune response?

Vaccines called high-dose, recombinant or adjuvanted flu vaccines can help people have a stronger immune response against influenza. People age 65 and older can get these vaccines. These vaccines also are recommended for people age 18 and older who have had a solid organ transplant and take medicine to weaken their immune response.

People age 50 and older may have the option to get a flu shot that uses messenger RNA (mRNA) to protect against flu. An mRNA vaccine tells your cells to make proteins from the outside of flu viruses but not the rest of the virus. This causes your body to create antibodies that are ready to respond to a real infection.

What if a child is getting a flu vaccine for the first time?

If a child is between ages 6 months and 8 years and has never had a flu vaccine or has had only one dose of a flu vaccine, the child may need two doses given at least four weeks apart. After that, the child can get single annual doses of the flu vaccine. Check with your child's healthcare professional.

When should I check with a healthcare professional before getting a flu vaccine?

Check with your healthcare team before getting a flu vaccine if you had a serious reaction to a previous flu vaccine. People who have had Guillain-Barre syndrome also should check with a healthcare professional before getting the flu vaccine. And if you feel sick when you go to get the shot, check with your healthcare professional to see if you should delay getting the vaccine.

If you have an egg allergy, you can receive any of the flu vaccines recommended for your age and health status anywhere the vaccine is offered.

What are my flu vaccine options?

The flu vaccine is available as a shot given with a needle, as a jet injection or as a nasal spray. For older children and adults, the flu shot is usually given in a muscle in the arm. Younger children may get the flu shot in a thigh muscle.

In the U.S., if you are an adult under the age of 65, you may be able to get your vaccine with a device called a jet injector. Instead of a needle, this device uses a high-pressure, narrow stream of fluid to give the vaccine through the skin.

The nasal spray vaccine is approved for people between 2 and 49 years old. The nasal flu vaccine isn't recommended for some people, including:

People who have severe asthma or are currently wheezing.
People who had a severe allergic reaction to a flu vaccine in the past.
People who are pregnant.
Young people who take aspirin or medicine that contains salicylates.
People with weakened immune systems and their caregivers or close contacts.
Children between 2 and 4 years old diagnosed with asthma or wheezing in the past 12 months.
People who recently took antiviral medicine for the flu.
People with a cerebrospinal fluid leak or the potential for a leak, as with a cochlear implant.

Check with your healthcare team to see if you need to be cautious about getting a nasal spray flu vaccine.

Can the vaccine give me the flu or other respiratory diseases?

No, the flu vaccine can't give you the flu. Getting the seasonal flu vaccine does not make you more likely to get another respiratory infection, based on available evidence.

But you might develop flu-like symptoms, despite getting a flu vaccine, for many reasons. These include:

Reaction to the vaccine. Some people have muscle aches, headache and a fever for a day or two after receiving a flu vaccine.
The two-week window. It takes about two weeks for the flu shot to take full effect. If you're exposed to the influenza virus shortly before or during that time period, you might catch the flu.
Mismatched flu viruses. In some years, the influenza viruses used for the vaccine don't match the viruses spreading during the flu season. If this occurs, your flu shot will be less effective. But it may still offer some protection.
Other illnesses. Many other illnesses, such as COVID-19, also have flu-like symptoms. That means you may think you have the flu when you do not.

What kind of protection does the flu vaccine offer?

How well the flu vaccine works to protect you from the flu can vary. Overall, seasonal vaccines prevent up to 60% of infections in healthy adults. The flu vaccine also lowers the number of people with an illness who need hospital care or who die of influenza. But that level of protection depends on the types of flu virus that are spreading, how well the vaccine matches those viruses, and your age and health.

Can I lower my risk of the flu without getting a flu shot?

The flu vaccine is your best defense against the flu. But you can take other steps to help protect yourself from the flu and other viruses, including COVID-19.

Wash your hands. Use soap and water if you can, and wash for at least 20 seconds. Or use a hand sanitizer with at least 60% alcohol.
Don't touch your face. Try to keep your hands away from your eyes, nose and mouth. Those are places where germs can get into the body.
Cover your coughs and sneezes. Cough or sneeze into a tissue or your elbow. Then wash your hands.
Clean surfaces. Regularly clean often-touched surfaces to prevent the spread of infection from touching a surface with the virus on it and then touching your face.

Also, try to lower the chance you'll come into contact with the flu virus. The flu spreads easily wherever people gather. When the flu is spreading, try to keep space between yourself and others while indoors, especially in areas with poor airflow. Try to avoid people who are sick or have flu symptoms.

If you get the flu, stay home if you can. Stay home until you feel better and have had no fever for a full 24 hours, and you haven't taken medicine for fever during that time. If your fever returns or you start to feel worse, stay apart from others until your symptoms improve and you are fever-free without medicine for 24 hours. Doing so lowers your chance of infecting others.

Planning for your seasonal flu vaccine

You may be able to get your flu vaccine at your healthcare professional's office. Other places to check are pharmacies, health centers and vaccine clinics at your school or workplace.