Influenza (flu) vaccine (Inactivated or Recombinant): What you need to know
All content below is taken in its entirety from the CDC Inactivated Influenza Vaccine Information Statement (VIS)
CDC review information for Inactivated Influenza VIS:
Page last updated: August 6, 2021
Why get vaccinated?
Influenza vaccine can prevent influenza (flu).
Flu is a contagious disease that spreads around the United States every year, usually between October and May. Anyone can get the flu, but it is more dangerous for some people. Infants and young children, people 65 years and older, pregnant people, and people with certain health conditions or a weakened immune system are at greatest risk of flu complications.
Pneumonia, bronchitis, sinus infections, and ear infections are examples of flu-related complications. If you have a medical condition, such as heart disease, cancer, or diabetes, flu can make it worse.
Flu can cause fever and chills, sore throat, muscle aches, fatigue, cough, headache, and runny or stuffy nose. Some people may have vomiting and diarrhea, though this is more common in children than adults.
In an average year, thousands of people in the United States die from flu, and many more are hospitalized. Flu vaccine prevents millions of illnesses and flu-related visits to the doctor each year.
2. Influenza vaccines
CDC recommends everyone 6 months and older get vaccinated every flu season. Children 6 months through 8 years of age may need 2 doses during a single flu season. Everyone else needs only 1 dose each flu season.
It takes about 2 weeks for protection to develop after vaccination.
There are many flu viruses, and they are always changing. Each year a new flu vaccine is made to protect against the influenza viruses believed to be likely to cause disease in the upcoming flu season. Even when the vaccine doesn't exactly match these viruses, it may still provide some protection.
Influenza vaccine does not cause flu.
Influenza vaccine may be given at the same time as other vaccines.
3. Talk with your health care provider
Tell your vaccination provider if the person getting the vaccine:
- Has had an allergic reaction after a previous dose of influenza vaccine, or has any severe, life-threatening allergies.
- Has ever had Guillain-Barré Syndrome (also called "GBS").
In some cases, your health care provider may decide to postpone influenza vaccination until a future visit.
Influenza vaccine can be administered at any time during pregnancy. People who are or will be pregnant during influenza season should receive inactivated influenza vaccine.
People with minor illnesses, such as a cold, may be vaccinated. People who are moderately or severely ill should usually wait until they recover before getting influenza vaccine.
Your health care provider can give you more information.
4. Risks of a vaccine reaction.
- Soreness, redness, and swelling where the shot is given, fever, muscle aches, and headache can happen after influenza vaccination.
- There may be a very small increased risk of Guillain-Barré Syndrome (GBS) after inactivated influenza vaccine (the flu shot).
Young children who get the flu shot along with pneumococcal vaccine (PCV13) and/or DTaP vaccine at the same time might be slightly more likely to have a seizure caused by fever. Tell your health care provider if a child who is getting flu vaccine has ever had a seizure.
People sometimes faint after medical procedures, including vaccination. Tell your provider if you feel dizzy or have vision changes or ringing in the ears.
As with any medicine, there is a very remote chance of a vaccine causing a severe allergic reaction, other serious injury, or death.
5. What if there is a serious problem?
An allergic reaction could occur after the vaccinated person leaves the clinic. If you see signs of a severe allergic reaction (hives, swelling of the face and throat, difficulty breathing, a fast heartbeat, dizziness, or weakness), call 9-1-1 and get the person to the nearest hospital.
For other signs that concern you, call your health care provider.
Adverse reactions should be reported to the Vaccine Adverse Event Reporting System (VAERS). Your health care provider will usually file this report, or you can do it yourself. Visit the VAERS website at
6. The National Vaccine Injury Compensation Program.
The National Vaccine Injury Compensation Program (VICP) is a federal program that was created to compensate people who may have been injured by certain vaccines. Claims regarding alleged injury or death due to vaccination have a time limit for filing, which may be as short as two years. Visit the VICP website at
7. How can I learn more?
- Ask your health care provider.
- Call your
local or state health department.
- Visit the website of the Food and Drug Administration (FDA) for vaccine package inserts and additional information at
Contact the Centers for Disease Control and Prevention (CDC):
- Call 1-800-232-4636 (1-800-CDC-INFO) or
- Visit CDC's influenza website at
Your head is throbbing. Your throat is burning. You're coughing nonstop, and your whole body aches. This is no run-of-the-mill cold. You may have the flu. Let's talk about influenza, also known as the flu. Winter is a time for sledding, snowball fights, and flu. Every winter, millions of Americans come down with this respiratory ailment and feel absolutely miserable. Like the common cold, the flu is caused by a virus. But with the flu, it's the influenza virus that makes people so sick. The flu virus comes in a few different forms. Influenza A is most common between early winter and spring. You can catch influenza B year-round. Swine flu, or H1N1, is a specific type of influenza A. You catch the flu from someone who has it. When people with the flu sneeze or cough, they send a spray of droplets filled with the flu virus into the air. If you're unlucky enough to be nearby, you could breathe in those droplets. Or, you might touch a surface that the droplets have fallen on and then touch your nose or mouth. Two to three days later, the first flu symptoms will appear. Usually you'll start running a fever. Then you'll feel achy and tired. You may have the chills and feel sick to your stomach. After a couple of days, the sore throat and cough will set in. So, how do doctors treat the flu? Because a virus causes the flu, antibiotics won't treat it, they only kill bacteria. There are antiviral medicines, but you need to start taking them within the first 2 days after your symptoms appear. Until the illness runs its course, help yourself feel better by getting a lot of rest and drinking extra fluids. You can take an over-the-counter cold medicine to relieve your congestion and cough. Tylenol, Advil, or Motrin can bring down your fever and take some of the pain out of your sore throat. Aspirin isn't recommended during the flu, especially under age 18, because it could increase the risk for a rare, but serious, condition called Reye syndrome. By itself, the flu usually isn't harmful. But it can make existing conditions like asthma and breathing problems worse. In older people or those with a weakened immune system, the flu can turn into pneumonia, bronchitis, and other more serious diseases. For most healthy people, the flu is a short-term annoyance. They're stuck in bed for a week or two, and then their symptoms go away and they're back up and around. But thousands of people each year get very sick from the flu, especially the elderly, young children, and pregnant women. Many are hospitalized, and about 36,000 people die from flu complications. To avoid getting the flu, eat well, get plenty of exercise and sleep, and practice good hygiene. Wash your hands often with warm water and soap or use an alcohol-based hand sanitizer. Don't share cups, plates, or utensils, especially during flu season. And most effective, get your flu shot every fall to protect you through the whole flu season.
Centers for Disease Control and Prevention website. Vaccine Information Statement. Influenza (Flu) Vaccine (Inactivated or Recombinant): What you need to know.
Last reviewed on: 8/6/2021
Reviewed by: Reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.