What Is the Flu?

Influenza — what most of us call "the flu" — is a contagious viral infection of the nose, throat, and lungs. It can make a person feel very sick.

When Should People Get the Flu Vaccine?

Flu viruses usually cause the most illness during the colder months of the year. In the United States, flu season is from October to May.

It's best to get the flu vaccine early in flu season, ideally by the end of October. This gives the body a chance to make antibodies that protect it from the flu. But getting a flu vaccine later in the season is better than not getting it at all.

Who Should Get the Flu Vaccine?

Everyone 6 months of age and older should get vaccinated against the flu each year.

Babies younger than 6 months can't get the vaccine. But they will be protected if their parents, other caregivers, and older kids in the household get it. This is important because infants who get the flu are more likely to have serious problems than older kids.

How Is the Flu Vaccine Given?

  • Kids younger than 9 years old who get the flu vaccine for the first time or who've had only 1 dose of the vaccine in the past will get 2 doses at least 1 month apart.
  • Kids younger than 9 who got at least 2 doses of flu vaccine (at any time) will only need 1 dose.
  • Kids older than 9 need only 1 dose of the vaccine.

Talk to your doctor about how many doses your child needs.

Where Can My Family Get the Flu Vaccine?

The flu vaccine usually is available at:

  • doctors' offices
  • public, employee, and university health clinics
  • most drugstores
  • some supermarkets and big-box stores
  • some community groups or centers
  • some schools

Some places that usually offer the vaccine might not do so during the 2020–2021 flu season because of the coronavirus pandemic. Check with your doctor, pharmacist, or local health department, or search online at Vaccine Finder to find a location near you.

What Are the Types of Flu Vaccines?

Two types of flu vaccine are available for the 2020–2021 flu season. Both protect against four types of influenza virus:

  • the flu shot, which is injected with a needle
  • the nasal spray, which is a mist sprayed into the nostrils

In past flu seasons, the nasal spray vaccine sometimes worked better or worse than the flu shot. The nasal spray available for the last two flu seasons appears to work as well as the shot. So kids can get either vaccine this year, depending on a child's age and general health.

Note: The nasal spray is only for healthy people ages 2–49. People with weak immune systems or some health conditions (such as asthma) and pregnant women should not get the nasal spray vaccine.

Why Is the Flu Vaccine Recommended?

While the flu vaccine isn't 100% effective, it still greatly lowers a person's chances of catching the flu, which can be very serious. It also can make symptoms less severe if someone who got the vaccine does still get the flu.

If you got the flu vaccine last year, it can't provide enough protection this year, because flu viruses change. That's why the vaccine is updated each year to include the most current types of the virus.

Sometimes the same virus types are included in the vaccine from one year to the next. Even then, it's still important to get the yearly flu vaccine because the body's immunity against the influenza virus declines over time.

Getting the flu vaccine not only protects you from the flu. It also helps protect the people and community around you. The flu vaccine makes someone less likely to get the flu, and therefore less likely to spread the flu. Getting the flu vaccine is a great way to protect people who are at risk from flu, such as the elderly, babies, and people with health conditions such as asthma. Every year thousands of people die from influenza, and getting the flu vaccine is one way to prevent that.

What Are the Possible Side Effects of the Flu Vaccine?

Both types of vaccine can cause mild side effects.

  • The flu shot usually is given as an injection in the upper arm or thigh (depending on a person's age). It contains killed flu virus and can't cause someone to get the flu. But it can cause soreness, redness, or swelling at the injection site. Rarely, it might cause a low fever or body aches.
  • The nasal spray flu vaccine contains weakened live flu viruses. So it may cause mild symptoms, such as a runny nose, wheezing, sore throat, vomiting, or tiredness. Like the shot, it can sometimes cause a low fever or body aches.

Sometimes, people faint after getting a shot, especially teenagers. It helps to sit or lie down for 15 minutes right after a shot to prevent this.

If your child has any side effects, talk to your doctor about giving either acetaminophen or ibuprofen and to find out the right dose.

A warm, damp cloth or a heating pad on the injection site may help ease soreness, as can moving or using the arm.

Very rarely, the flu vaccine can cause a serious allergic reaction.

What Else Should I Know?

Some things might prevent a person from getting the flu vaccine. Talk to your doctor to see if the vaccine is still recommended if your child:

Egg Allergy and the Flu Vaccine

In the past, people with an egg allergy had to check with their doctor about whether the flu vaccine was OK for them because it's grown inside eggs. But health experts now say that the amount of egg protein in the vaccine is so tiny that it's safe even for kids with a severe egg allergy.

Still, a child with an egg allergy should get the flu vaccine in a doctor's office, not at a supermarket, drugstore, or other venue.

Getting a Flu Vaccine During the COVID-19 Pandemic

As coronavirus continues to spread during this 2020-2021 flu season, it's extra important to get a flu vaccine for all family members:

  • Preventing flu will help you avoid needing medical care when health care providers are so busy caring for people with COVID-19.
  • Health experts worry that people who get the flu and COVID-19 at the same time might have a more serious illness.
  • Flu and COVID-19 cause similar symptoms. Preventing the flu and its symptoms means that your family will be less likely to need testing (for flu or coronavirus) or to isolate at home.

When Should I Call the Doctor?

Call your doctor if:

  • Your child is sick and has a fever, and you aren't sure whether to reschedule the vaccine. Kids with a mild illness, like a cold, usually can still get the vaccine.
  • Your child has problems after the immunization, such as an allergic reaction or high fever, or if you have other concerns.
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Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor. © 1995-2021 KidsHealth®. All rights reserved. Images provided by The Nemours Foundation, iStock, Getty Images, Veer, Shutterstock, and Clipart.com.