A flu vaccine protects people from developing influenza (flu). Flu is a contagious respiratory (breathing) illness. A flu vaccine causes a person to develop antibodies that recognize and fight flu viruses. This builds up the body’s natural defenses (immunity) against infection.
People need a flu vaccine once a year. This is because the vaccine is different each year. Flu viruses change over time, so the vaccine from last year may not work as well for the next year. Also, your body’s immune response decreases over time.
A vaccine strengthens the immune system to protect the body from illness. The flu vaccine helps protect people from developing the flu. Some people may still get the flu after being vaccinated. Even if you do get the flu, you may not get as sick. This is because your body is better able to defend itself after getting the vaccine.
Most people who get flu get better in a few days to less than 2 weeks. But some people develop more serious problems or complications. Some problems can be life threatening.
Sinus and ear infections are examples of moderate complications from the flu. Pneumonia is an example of a serious flu complication.
Flu vaccination is especially important for people with certain medical conditions, including:
The flu can make these medical problems worse. For example, people with asthma may get asthma attacks while they have the flu. People with heart disease may have an increased heart attack risk because of the flu.
There are 2 main ways the flu vaccine is given:
Flu shot (needle injection):
Nasal spray (Flumist®):
Your health care provider will recommend the best flu vaccine for your child.
Mild side effects are normal after a flu vaccine. Symptoms may include:
Flu vaccines do not give you the flu. Side effects are usually mild and go away after a few days. This is because the immune system is responding to the vaccine. The body is making antibodies against the flu.
If possible, get the flu shot in September or October, or as soon as it becomes available. If you don’t get a flu shot early, getting one any time during the flu season will help protect you. In general, flu cases in the U.S. start to rise in October, peak in December through February, and can last until May.
It takes about 2 weeks to develop an immune response after getting the flu vaccine. In certain cases, children may need 2 doses of the flu vaccine. Your health care provider will tell you if another dose is needed.
Medical experts advise that most children with serious illnesses and all children 6 months and older get yearly flu shots. The Centers for Disease Control and Prevention, the American Academy of Pediatrics, and the Infectious Diseases Society of America agree on this advice. It is important to remember that the vaccine is usually not harmful.
Ask your child’s care team when to give your child the flu vaccine. Your child might not respond to the flu vaccine if they have had:
Transplant, cellular (CAR T-cell) therapy, and gene therapy patients can get a flu shot 6 months after their infusion. If there is a flu outbreak in the community, they can get a flu shot 4 months after transplant.
Depending on your child’s diagnosis and treatment plan, the care team will advise when your child should get the flu shot. Talk to your child’s care team about your child’s specific situation.
Flu vaccines for family members
If you have a child with a serious illness, it is important for family members and those in close contact with your child to get the flu vaccine. Young children and those with serious illnesses are at higher risk for life-threatening complications from the flu.
Getting all family members and caregivers vaccinated helps to create a circle of protection around your child.
The Centers for Disease Control and Prevention (CDC) recommend that everyone 6 months and older with an egg allergy should get the flu vaccine. Any flu vaccine (egg based or non-egg based) can be used.
It is possible to have both the flu and COVID-19 at the same time. Both COVID-19 and the flu are respiratory infections. The symptoms of COVID-19 and the flu can be the same.
The flu vaccine will not protect you from COVID-19. And the COVID-19 vaccine will not protect you from the flu.
If you have symptoms, your care team will likely test for both illnesses. The test results can help your care team decide the best treatment.
—
TheTogether by St. Jude™ online resource does not endorse any branded product mentioned in this article.
—
Reviewed: January 2024
The immune system is the body's defense against infection. A network of special cells, tissues, and organs work together to protect the body from a variety of "invaders" or germs.
Influenza (flu) is a respiratory illness caused by a virus. Some people are at higher risk for flu complications. Learn how to prevent and treat the flu.
Vaccines are an important way to protect against certain illnesses. Learn about immunization schedules and vaccines in children with cancer and other illnesses.