Flu Shot: Your Best Bet to Avoid the Flu

The flu vaccine often protects you from a serious case of the flu. And while the flu vaccine doesn't always provide complete protection, it's worth getting.

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By Mayo Clinic Staff

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

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Getting a flu shot is the best way to prevent the flu and its complications for almost everyone. The flu shot can reduce the risk of getting the flu. It can also reduce the risk of developing serious illness from the flu and of needing to stay in the hospital or dying from the flu.

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

When is the flu vaccine available?

The flu vaccine is often available in the United States around September. The viruses that cause influenza spread at high levels at certain times of the year in both the Northern and Southern Hemispheres. These are called flu seasons. In North America, flu season typically lasts from October to May.

It takes pharmaceutical manufacturers about six months to produce the 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 develop immunity, so it's generally best for Americans to get their flu shot in September or October. But you can still benefit from the vaccine even if you don't get it until later in the flu season.

Why do I need to get vaccinated every year?

Flu viruses change rapidly. Last year's vaccine may not protect you from this year's viruses. New flu vaccines are released each year to keep up with the rapid changes in flu viruses.

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

Who should get the flu vaccine?

The U.S. Centers for Disease Control and Prevention recommends annual seasonal influenza vaccination for everyone 6 months of age and older who has no medical reason to avoid the vaccine.

Getting vaccinated against the flu every year reduces the risk of serious complications or death from the flu. This is especially true for people who are at high risk of complications from the flu.

High-risk groups include:

• Adults over 65 years old.
• People living in nursing homes or long-term care facilities.
• Young children, especially those aged 12 months or younger.
• People who are planning to become pregnant, are pregnant, or have recently given birth during flu season.

In the United States, certain groups are at higher risk of needing hospital treatment for influenza. These groups include American Indian or Alaska Native people, black people, and Latino people.

Other groups at high risk for influenza-related complications include people with:

• A weakened immune system.
• A body mass index (BMI) of 40 or more.
• Conditions that affect the nervous system or the way the brain processes information.

And people with certain medical conditions are at higher risk of flu complications, such as:

• People with chronic diseases, such as asthma, heart disease, kidney disease, liver disease and diabetes.
• People who have had a stroke.
• People under 20 years of age who are taking long-term aspirin treatment.

High-dose or adjuvanted flu vaccines can help people strengthen their immune response to the flu. People over 65 years of age can receive these vaccines. These vaccines are also recommended for people 18 years of age and older who have had a solid organ transplant and are taking medications to weaken their immune response.

Children ages 6 months to 8 years may need two doses of the flu vaccine, given at least four weeks apart, the first time they get a flu shot. After that, they may receive a single annual dose of the flu vaccine. Check with your child's healthcare provider.

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

If you have an egg allergy, you can get any flu vaccine, anywhere the vaccine is offered.

What are my flu vaccine options?

The flu vaccine is available as an injection given with a needle, as a jet injection, or as a nasal spray.

For older children and adults, the flu vaccine is usually given into a muscle in the arm. Younger children may get the vaccine into a muscle in the thigh.

If you are an adult under 65, you can get vaccinated with a jet injection device. Instead of a needle, the device uses a narrow stream of high-pressure fluid to pass through the skin.

The nasal spray vaccine is approved for people ages 2 to 49. The nasal flu vaccine is not recommended for certain people, including:

• People who have had a serious allergic reaction to a flu vaccine in the past.
• Pregnant people.
• Young people taking aspirin or any medicine containing salicylate.
• People with weakened immune systems and people who care for or are in close contact with people with weakened immune systems.
• Children aged 2 to 4 years who have been diagnosed with asthma or wheezing in the past 12 months.
• People who have recently taken an antiviral medication for influenza.
• People with a cerebrospinal fluid leak or risk of leakage, such as with a cochlear implant.

Check with your healthcare team to see if you need to be careful when getting the nasal spray flu vaccine.

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

No, the flu vaccine cannot give you the flu. And the flu vaccine does not make you more likely to get any other respiratory infection, based on available data.

But you could develop flu-like symptoms, despite the flu vaccine, for many reasons, including:

• Reaction to the vaccine. Some people experience muscle aches and fever for a day or two after getting the flu vaccine. This may be a side effect of your body producing protective antibodies.
• The two-week window. It takes about two weeks for the flu vaccine to take full effect. If you are exposed to the flu virus close to or during this time, you could get the flu.
• Incompatible influenza viruses. Some years, the flu viruses used in the vaccine don't match the viruses that are spread during flu season. If this happens, your flu vaccine will be less effective. But it may still provide some protection.
• Other diseases. Many other illnesses, such as COVID-19, also have flu-like symptoms, so you may think you have the flu when you don't.

What type of protection does the flu vaccine offer?

The effectiveness of the flu vaccine in protecting you against the flu can vary. Reviews of flu season data since 2009 show that vaccine protection ranges from a low of 22 % to a high of 56 %. For the U.S. population, that means millions fewer illnesses and visits to health care providers. The flu vaccine also reduces the number of people who get sick and need hospital care or die from the flu.

Can I reduce my risk of flu without getting vaccinated?

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

Follow these standard precautions:

• Wash your hands. Wash your hands thoroughly and often with soap and water for at least 20 seconds. If soap and water are not available, use an alcohol-based hand sanitizer that contains at least 60% alcohol. Make sure friends and family you spend time with, especially children, know the importance of hand washing.
• Avoid touching your face. Keeping your hands away from your eyes, nose, and mouth helps keep germs away from these areas.
• Cover your cough and sneeze. Cough or sneeze into a tissue or your elbow. Then wash your hands.
• Clean the surfaces. Clean frequently touched surfaces regularly to prevent the spread of infection by touching a surface that contains the virus and then your face.
• Avoid crowds. The flu spreads easily anywhere people gather: in daycares, schools, office buildings, auditoriums, and on public transportation. Avoiding crowds during peak flu season can help reduce your risk of infection.

Also avoid anyone who is sick.

If you are sick, stay home until you feel better and have been fever-free for 24 hours, and have not taken fever-reducing medicine during that time. If your fever returns or you start to feel worse, stay away from others until your symptoms improve and you have been fever-free without medicine for 24 hours. This will reduce your risk of infecting others.

Flu Shots at Mayo Clinic

The Mayo Clinic offers flu vaccines in Arizona, Florida and Minnesota.

Learn more about how to get a flu shot at the Mayo Clinic.

Planning Your Seasonal Flu Vaccine

For almost everyone, a flu shot can reduce the risk of flu and its complications. You may be able to get the flu shot at your health care provider's office. Other places to check include pharmacies, health centers, and vaccination clinics at your school or workplace.

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