Flu shot: Your best bet for avoiding influenza

Getting a flu shot will often protect you from a serious case of the flu. And although the flu shot doesn't always provide total protection, it's worth getting.

By Mayo Clinic Staff

This year's annual flu shot will provide protection against four of the influenza viruses expected to be most common during this flu season. High-dose flu vaccines will be available for adults age 65 and older.

Influenza, often called the flu, is an infection of the nose, throat and lungs, also called the respiratory system. Influenza can cause serious complications, especially in children age 2 or younger, pregnant people, adults over age 65 and people with certain medical conditions. By some estimates, the flu causes more than 400,000 hospital stays and 50,000 deaths every year.

Getting an influenza vaccine — though not 100% effective — is the best way to prevent the misery of the flu and its complications. The Centers for Disease Control and Prevention (CDC) recommends annual flu vaccination for everyone age 6 months or older. The flu vaccine can lower your risk of getting the flu. It also can lower the risk of having serious illness from the flu and needing to stay in the hospital.

Here are the answers to common questions about flu shots:

When is the flu vaccine available?

Private manufacturers make the flu vaccine. It takes about six months. The availability of the flu vaccine depends on when production is completed. But generally, shipments begin sometime in August each year in the United States. Health care providers may begin vaccinating people as soon as the flu vaccine is available in their areas.

It takes up to two weeks to build immunity after a flu shot. But you can benefit from the vaccine even if you don't get it until after the flu season starts. It's usually best for people in the United States to get the flu vaccine in September and October. Aim to get it by the end of October. But you can still protect yourself against late flu outbreaks if you get the vaccine in February or later.

Why do I need to get vaccinated every year?

Because flu viruses change so 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 — another reason to get a flu shot every year.

Who should get the flu vaccine?

The CDC recommends annual influenza vaccinations for everyone age 6 months or older. Vaccination is especially important for people at high risk of influenza complications, including:

  • Children younger than age 2
  • Adults older than age 50
  • Residents of nursing homes and other long-term care facilities
  • People who are pregnant or plan to be pregnant during flu season
  • People with weakened immune systems
  • People age 6 months to 18 years who take aspirin or salicylate-containing medication
  • American Indians or Alaska natives
  • People who have chronic illnesses, such as asthma, heart disease, kidney disease, liver disease and diabetes
  • People with a body mass index (BMI) of 40 or higher

Children between 6 months and 8 years may need two doses of the flu vaccine, given at least four weeks apart, the first time they are given a flu vaccine. After that, they can receive single annual doses of the flu vaccine. Check with your child's health care provider.

Chronic medical conditions also can increase your risk of influenza complications. Examples include:

  • Asthma
  • Cancer or cancer treatment
  • Chronic obstructive pulmonary disease (COPD)
  • Heart disease
  • Cystic fibrosis
  • Diabetes
  • Brain or nervous system conditions
  • HIV or conditions that are treated by lowering the immune system
  • Kidney or liver disease
  • Obesity, including people with a BMI of 40 or higher

Anyone with a chronic medical condition should get the flu vaccine. Also, people living in nursing homes or other long-term care facilities should get the flu vaccine.

Check with your health care provider before receiving a flu vaccine if:

  • You had a severe reaction to a previous flu vaccine. The flu vaccine isn't recommended for anyone who had a severe reaction to a previous flu vaccine. Check with your health care provider first, though. Some reactions might not be related to the vaccine.

If you have an egg allergy, you can still receive the flu vaccine.

What are my flu vaccine delivery options?

The flu vaccine will be available as a shot, also called an injection, or as a nasal spray.

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:

  • Children younger than age 2
  • Adults age 50 and older
  • Pregnant people
  • Children between 2 and 17 years old who are taking aspirin or a salicylate-containing medication
  • People with weakened immune systems
  • Kids 2 to 4 years old who have had asthma or wheezing in the past 12 months

There are people in other groups who may need to be cautious about the use of a nasal spray flu vaccine, such as people with certain chronic medical conditions. Check with your health care provider to see if you need to be cautious about getting a nasal spray flu vaccine.

You also can get the flu vaccine as a shot that's usually given in a muscle in the arm. If you're an adult under 65, you can choose to get your vaccine with a jet injector device, which uses a high-pressure, narrow stream of fluid to go through the skin instead of a needle.

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

No. The flu vaccine can't give you the flu. It also doesn't increase your risk of COVID-19. But you might develop flu-like symptoms — despite getting a flu vaccine — for many reasons, including:

  • Reaction to the vaccine. Some people have muscle aches and a fever for a day or two after receiving a flu vaccine. This may be a side effect of your body's production of protective antibodies.
  • 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 the common cold, also have flu-like symptoms. So you may think you have the flu when you actually don't.

What kind of protection does the flu vaccine offer?

How well the flu vaccine works to protect you from the flu can vary. The standard flu vaccine is generally more effective among people younger than 65. Some older people and people with certain medical conditions may develop less immunity after receiving a flu shot.

High-dose flu vaccines are a type of vaccine approved for people age 65 and older. They can help people in this group have a stronger immune system response against flu viruses.

Reviews of past studies have found that the flu vaccine is about 50% effective for healthy adults who are between 18 and 64 years old. The vaccine may sometimes be less effective.

Even when the vaccine doesn't completely prevent the flu, it may lessen the severity of your illness. It also may lower the risk of serious complications and serious illness needing hospital stays.

Also, flu vaccination could lessen symptoms that might be confused with those caused by COVID-19. Preventing the flu and lowering the number of people with severe flu and flu complications also could lower the number of people needing to stay in the hospital.

And if a COVID-19 vaccine or booster and a flu vaccination end up due at the same time, the CDC reports that you can get vaccinated for both in one visit.

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

The flu vaccine is your best defense against the flu. But there are more steps you can take to help protect yourself from the flu and other viruses, including COVID-19. Follow these standard precautions:

  • Get vaccinated. Both COVID-19 and the flu may be spreading at the same time. Vaccination is the best way to protect against both.
  • Wash your hands often and thoroughly with soap and water for at least 20 seconds.
  • Use an alcohol-based sanitizer on your hands if soap and water aren't available.
  • Avoid touching your eyes, nose or mouth.
  • Avoid crowds when the flu or COVID-19 is spreading in your area.
  • Avoid being in close contact with others who are sick.
  • Cover your mouth with a tissue or the inside of your elbow when you cough or sneeze, and then wash your hands.
  • Regularly clean and disinfect commonly touched surfaces, such as counters, light switches and doorknobs. This can help to prevent the spread of infection from touching a surface with the virus on it and then touching your face.
  • Practice good health habits. Get regular exercise, get enough sleep, drink plenty of fluids, eat a healthy diet and manage stress.

If you become sick with the flu, you can also help prevent the spread of the flu by staying home and away from others. Continue staying home until your fever has been gone for at least 24 hours.

Getting your flu vaccine can lower your risk of the flu and its complications. Following these precautions can help protect you from the flu or other respiratory illnesses.

Flu vaccines at Mayo Clinic

Mayo Clinic offers flu shots in Arizona, Florida and Minnesota.

Learn more about how to get your flu shot at Mayo Clinic

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Oct. 26, 2022 See more In-depth