Seasonal Flu Shot
Note: “Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2019–20 Influenza Season” has been published. CDC recommends annual influenza vaccination for everyone 6 months and older with any licensed, influenza vaccine that is appropriate for the recipient’s age and health status, (IIV, RIV4, or LAIV4) with no preference expressed for any one vaccine over another. Content on this website is being updated to reflect this most recent guidance. More information about the upcoming 2019-2020 flu season is available.
An influenza shot is a vaccine given with a needle, usually in the arm. Seasonal influenza shots protect against the three or four influenza viruses that research indicates will be most common during the season.
There are different influenza vaccine manufacturers and multiple influenza vaccine products licensed and recommended for use in the United States.
CDC recommends use of any licensed, age-appropriate influenza vaccine during the 2019-2020 influenza season, including inactivated influenza vaccine [IIV], recombinant influenza vaccine [RIV], or live attenuated influenza vaccine (LAIV). No preference is expressed for any influenza vaccine over another. Both trivalent (three-component) and quadrivalent (four-component) influenza vaccines will be available.
Trivalent influenza vaccines include:
- A trivalent influenza shot made with adjuvant (Fluad), licensed for people 65 years and older.
- A high-dose influenza vaccine (Fluzone High-Dose), licensed for people 65 years and older.
Quadrivalent flu vaccines include:
- Standard-dose quadrivalent influenza shots that are manufactured using virus grown in eggs. These include Afluria Quadrivalent, Fluarix Quadrivalent, FluLaval Quadrivalent, and Fluzone Quadrivalent. Different influenza shots are licensed for different age groups. Some are licensed for children as young as 6 months of age. Most influenza shots are given in an arm muscle with a needle. One quadrivalent influenza shot (Afluria Quadrivalent) can be given either with a needle (for people aged 6 months and older) or with a jet injector (for people aged 18 through 64 years only).
- A quadrivalent cell-based influenza shot (Flucelvax Quadrivalent) containing virus grown in cell culture, which is licensed for people 4 years and older. This season, all four of the vaccine viruses used in Flucelvax have been grown in cells, making the vaccine totally egg-free.
- Recombinant quadrivalent influenza shot (Flublok Quadrivalent), an egg-free vaccine, approved for people 18 years and older.
There are many vaccine options to choose from, but the most important thing is for all people 6 months and older to get an influenza vaccine every year. If you have questions about which vaccine is best for you, talk to your doctor or other health care professional. More information on approved influenza vaccines for the 2019-2020 influenza season, and age indications for each vaccine are available in CDC’s Table: U.S. Influenza Vaccine Products for the 2019-20 Season
More information on who should and who should not get an influenza vaccine is available.
Influenza vaccine effectiveness (VE) can vary from season to season. The protection provided by an influenza vaccine depends on the age and health status of the person getting the vaccine, and the similarity or “match” between the viruses used to produce vaccine and those in circulation.
While influenza vaccine varies in how well it works, every season influenza vaccines prevent millions of influenza illnesses, tens of thousands of hospitalizations and thousands of deaths.
- What is the flu shot?
- Is there more than one type of flu shot available?
- Who should and who should not get an influenza vaccine?
- What are the side effects that could occur?
- Can severe problems occur?
- What should I do if I have had a serious reaction to seasonal influenza vaccine?
- Why do some people not feel well after getting the flu shot?
- What about people who get a flu shot and still get sick with flu symptoms?
- What protection does the flu vaccine provide if I do get sick with flu?
- Egg Allergy
Common side effects from a flu shot include soreness, redness, and/or swelling where the shot was given, headache (low grade), fever, nausea, muscle aches, and fatigue. The flu shot, like other injections, can occasionally cause fainting.
Life-threatening allergic reactions to influenza shots are very rare. Signs of serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness. If they do occur, it is usually within a few minutes to a few hours after receiving the shot. These reactions can occur among persons who are allergic to something that is in the vaccine, such as egg protein or other ingredients. While severe reactions are uncommon, you should let your doctor, nurse, clinic, or pharmacist know if you have a history of allergy or severe reaction to influenza vaccine or any part of influenza vaccine.
There is a small possibility that influenza vaccine could be associated with Guillain-Barré syndrome, generally no more than 1 or 2 cases per million people vaccinated. This is much lower than the risk of severe complications from influenza, which can be prevented by influenza vaccine.
Call a doctor or get to a doctor right away.
Tell your doctor what happened, the date and time it happened, and when you got the flu shot.
Ask your doctor, nurse, or health department to file a Vaccine Adverse Event Reporting Systemexternal icon (VAERS) form, or call VAERS at 1-800-822-7967. Reports are welcome from all concerned individuals: patients, parents, health care providers, pharmacists and vaccine manufacturers.
Influenza vaccine side effects are generally mild and go away on their own within a few days. Some side effects that may occur from an influenza shot include soreness, redness, and/or swelling where the shot was given, headache (low grade), fever, nausea, muscle aches, and fatigue. The influenza shot, like other injections, can occasionally cause fainting.
It’s possible to get sick with flu even if you have been vaccinated (although you won’t know for sure unless you get a flu test). This is possible for the following reasons:
- You may be exposed to an influenza virus shortly before getting vaccinated or during the period that it takes the body to gain protection after getting vaccinated. This exposure may result in you becoming ill with influenza before the vaccine begins to protect you. (Antibodies that provide protection develop in the body about 2 weeks after vaccination.)
- You may be exposed to an influenza virus that is different from what is used to make seasonal influenza vaccine. There are many different influenza viruses that circulate every year. An influenza vaccine is made to protect against the three or four influenza viruses that research suggests will be most common.
- Unfortunately, some people can become infected with an influenza virus that the influenza vaccine is designed to protect against, despite getting vaccinated. Protection provided by influenza vaccination can vary widely, based in part on health and age factors of the person getting vaccinated. In general, an influenza vaccine works best among healthy younger adults and older children. Some older people and people with certain chronic illnesses may develop less immunity after vaccination. Influenza vaccination is not a perfect tool, but it is the best way to protect against influenza infection.
Some people who get vaccinated may still get sick. However, influenza vaccination has been shown in some studies to reduce severity of illness in people who get vaccinated but still get sick:
- A 2017 study showed that influenza vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized influenza patients.
- Another study in 2018 showed that a vaccinated adult who was hospitalized with influenza was 59 percent less likely to be admitted to the Intensive Care Unit than someone who had not been vaccinated. Among adults in the ICU with influenza, vaccinated patients on average spent 4 fewer days in the hospital than those who were not vaccinated.
In addition, it’s important to remember that influenza vaccine protects against 3 or 4 different viruses and multiple viruses usually circulate during any one season. For these reasons, CDC continues to recommend influenza vaccination for everyone 6 months and older even if vaccine effectiveness against one or more viruses is reduced.
People with egg allergies can receive any licensed, recommended age-appropriate influenza vaccine (IIV, RIV4, or LAIV4) that is otherwise appropriate. People who have a history of severe egg allergy (those who have had any symptom other than hives after exposure to egg) should be vaccinated in a medical setting, supervised by a health care provider who is able to recognize and manage severe allergic reactions.