Flu (Influenza)

Every year, millions of people get the flu. The good news is that the seasonal flu vaccine can lower the risk of getting the flu by about half. Getting the yearly flu vaccine is the best way to protect yourself from the flu.

Why is the flu vaccine important?


Most people who get the flu have a mild illness. But for some, it can be serious — and even deadly. Serious complications from the flu are more likely in babies and young children, pregnant women, older adults, and people with certain long-term health conditions — like diabetes or asthma.

Getting vaccinated every year is the best way to lower your chances of getting the flu. Flu vaccines can’t cause the flu. Keep in mind that getting the flu vaccine also protects the people around you. So when you and your family get vaccinated, you help keep yourselves and your community healthy.

This is especially important if you spend time with people who are at risk for serious illness from the flu — like young children or older adults. Learn more about how vaccines help protect your whole community.

What is the flu?

The flu is caused by a virus. Common symptoms of the flu include:

  • Fever and chills
  • Cough
  • Sore throat
  • Runny or stuffy nose
  • Muscle or body aches
  • Headache
  • Feeling very tired

Some people with the flu may throw up or have diarrhea (watery poop) — this is more common in children than adults. It’s also important to know that not everyone with the flu will have a fever.

The flu is worse than the common cold. It’s a common cause of problems like sinus or ear infections. It can also cause serious complications like:

  • Pneumonia (lung infection)
  • Worsening of long-term health problems, like asthma or heart failure
  • Inflammation of the brain, heart, or muscles
  • Sepsis, a life-threatening inflammatory condition
  • Multi-organ failure

The flu is contagious, meaning it can spread from person to person. The flu can spread when:

  • Someone with the flu coughs, sneezes, or talks — and droplets from their mouth or nose get into the mouths or noses of people nearby
  • Someone touches a surface that has flu virus on it and then touches their mouth, nose, or eyes

People can spread the flu before they know they’re sick — and while they have the flu. Learn more about the flu .

Who needs to get the flu vaccine?

Everyone age 6 months and older needs to get the flu vaccine every year. It's part of the routine vaccine schedules for children, teens, and adults.

See the routine vaccination schedule for:

It’s important to get the flu vaccine every year. That’s important for 2 reasons: first, immunity (protection) decreases with time. Additionally, the flu viruses are constantly changing — so the vaccine is often updated to give the best protection.

People at increased risk for complications from the flu

It’s especially important for people who are at high risk of developing complications from the flu to get the vaccine every year. People at high risk for complications from the flu include:

  • Pregnant women — including women up to 2 weeks after the end of pregnancy
  • Adults age 65 years and older
  • Children younger than 5 years — and especially children younger than 2 years
  • People with long-term health conditions like asthma, diabetes, or cancer
  • People in long-term care or nursing homes

Aim to get your flu vaccine by the end of October

Try to get the flu vaccine by the end of October. It takes 2 weeks for your body to develop immunity. So it’s best to get the flu vaccine before the flu starts to spread in your community.

If you don’t get the vaccine by the end of October, that doesn’t mean you shouldn’t get it — getting vaccinated later can still help protect you from the flu. You can get vaccinated at any time throughout the flu season.

Health care professionals and caregivers

It’s also very important for people who spend a lot of time with people at high risk for complications from the flu to get the vaccine — for example, health care professionals and caregivers.

Talk with your doctor about how to protect your family from the flu.

Who should not get the flu vaccine?

Children younger than 6 months should not get the flu vaccine.

Be sure to tell your doctor before getting vaccinated if you:

  • Have had a life-threatening allergic reaction to a dose of the flu vaccine or any ingredient in the vaccine (like eggs or gelatin)
  • Have had Guillain-Barré Syndrome (an immune system disorder)

If you’re sick, you may need to wait until you’re feeling better to get the flu vaccine.

What are the side effects of the flu vaccine?

Side effects are usually mild and go away in a few days. These side effects aren’t the flu — the flu vaccine can’t cause the flu.

Side effects from the flu vaccine may include:

  • Pain, swelling, or redness where the shot was given
  • Headache
  • Muscle aches
  • Fever
  • Upset stomach

Serious side effects from the flu vaccine are very rare.

Like any medicine, there's a very small chance that the flu vaccine could cause a serious reaction. Keep in mind that getting the flu vaccine is much safer than getting the flu. Learn more about vaccine side effects .

Get vaccinated

Getting vaccinated is easy. Vaccines are available at the doctor’s office and many pharmacies — and most are covered by insurance.

Find out how to get vaccinated.

Content created by Office of Infectious Disease and HIV/AIDS Policy (OIDP)
Content last reviewed