The single best way to protect against the flu is to get vaccinated each year.
\nInfluenza is a potentially serious disease that can lead to hospitalization and sometimes even death. Every flu season is different, and influenza infection can affect people differently, but millions of people get the flu every year, hundreds of thousands of people are hospitalized and thousands or tens of thousands of people die from flu-related causes every year. An annual seasonal flu vaccine is the best way to help protect against flu. Vaccination has been shown to have many benefits including reducing the risk of flu illnesses, hospitalizations and even the risk of flu-related death in children.
\nFlu vaccines cause antibodies to develop in the body about two weeks after vaccination. These antibodies provide protection against infection with the viruses that are in the vaccine.
\nThe seasonal flu vaccine protects against the influenza viruses that research indicates will be most common during the upcoming season. Traditional flu vaccines (called \u201ctrivalent\u201d vaccines) are made to protect against three flu viruses; an influenza A (H1N1) virus, an influenza A (H3N2) virus, and an influenza B virus. There are also flu vaccines made to protect against four flu viruses (called \u201cquadrivalent\u201d vaccines). These vaccines protect against the same viruses as the trivalent vaccine and an additional B virus.
\nCDC recommends use of any licensed, age-appropriate influenza vaccine during the 2018-2019 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) flu vaccines will be available.
\nTrivalent flu vaccines include:
\nQuadrivalent flu vaccines include:
\nFor the 2018-2019 flu season, the Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for everyone 6 months and older with any licensed age-appropriate flu vaccine including inactivated influenza vaccine (IIV), recombinant influenza vaccine (RIV4) or live attenuated influenza vaccine (LAIV4) with no preference expressed for any one vaccine over another.
\nEveryone 6 months of age and older should get a flu vaccine every season. This recommendation has been in place since February 24, 2010 when CDC\u2019s Advisory Committee on Immunization Practices (ACIP) voted for \u201cuniversal\u201d flu vaccination in the United States to expand protection against the flu to more people.
\nVaccination to prevent influenza is particularly important for people who are at high risk of serious complications from influenza. See People at High Risk of Developing Flu-Related Complications for a full list of age and health factors that confer increased risk.
\nMore information is available at Who Should Get Vaccinated Against Influenza.
\nDifferent flu vaccines are approved for use in different age groups. In addition, some vaccines are not recommended for certain groups. Factors that can determine a person\u2019s suitability for vaccination, or vaccination with a particular vaccine, include a person\u2019s age, health (current and past) and any allergies to flu vaccine or its components.
\n \nYou should get a flu vaccine before flu begins spreading in your community. It takes about two weeks after vaccination for antibodies that protect against flu to develop in the body. CDC recommends that people get a flu vaccine by the end of October. Getting vaccinated later, however, can still be beneficial and vaccination should continue to be offered throughout the flu season, even into January or later.
\nChildren who need two doses of vaccine to be protected should start the vaccination process sooner, because the two doses must be given at least four weeks apart.
\nFlu vaccines are offered in many doctor\u2019s offices, clinics, health departments, pharmacies and college health centers, as well as by many employers, and even in some schools.
\nEven if you don\u2019t have a regular doctor or nurse, you can get a flu vaccine somewhere else, like a health department, pharmacy, urgent care clinic, and often your school, college health center, or workplace.
\nVisit the HealthMap Vaccine Finder to locate where you can get a flu vaccine.
\nA flu vaccine is needed every season for two reasons. First, the body\u2019s immune response from vaccination declines over time, so an annual vaccine is needed for optimal protection. Second, because flu viruses are constantly changing, the formulation of the flu vaccine is reviewed each year and updated as needed to keep up with changing flu viruses. For the best protection, everyone 6 months and older should get vaccinated annually.
\nNo. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection. That\u2019s why it\u2019s better to get vaccinated by the end of October, before the flu season really gets under way.
\n \n Top of Page \nInfluenza vaccine effectiveness (VE) can vary from year to year. The protection provided by a flu vaccine depends on the age and health status of the person getting the vaccine, and the similarity or \u201cmatch\u201d between the viruses or virus in the vaccine and those in circulation. For more information, see Vaccine Effectiveness \u2013 How well does the Flu Vaccine Work.
\nYes. It\u2019s possible to get sick with flu even if you have been vaccinated (although you won\u2019t know for sure unless you get a flu test). This is possible for the following reasons:
\nSome people who get vaccinated may still get sick. However, flu 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 flu vaccination reduced deaths, intensive care unit (ICU) admissions, ICU length of stay, and overall duration of hospitalization among hospitalized flu patients. Another study in 2018 showed that a vaccinated adult who was hospitalized with flu 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 flu, vaccinated patients on average spent 4 fewer days in the hospital than those who were not vaccinated. In addition, it\u2019s important to remember that flu vaccine protects against three or 4 different viruses and multiple viruses usually circulate during any one season. For these reasons, CDC continues to recommend flu vaccination for everyone 6 months and older even if vaccine effectiveness against one or more viruses is reduced.
\n \n Top of Page \nThere are many reasons to get a flu vaccine each year. Below is a summary of the benefits of flu vaccination, and selected scientific studies that support these benefits.
\n*References for the studies listed above can be found at Publications on Influenza Vaccine Benefits. Also, see the Why Get a Flu Vaccine [237 KB, 2 pages] fact sheet.
\nA \u201cgood match\u201d is said to occur when the flu viruses the flu vaccine is designed to protect against and the viruses circulating among people during a given influenza season are closely related and the antibodies produced by vaccination protect against infection.
\nDuring seasons when one or more of the circulating viruses are different or \u201cdrifted\u201d from the vaccine viruses, vaccine effectiveness against the drifted viruses can be reduced.
\nFlu viruses are constantly changing (called \u201cantigenic drift\u201d) \u2013 they can change from one season to the next or they can even change within the course of one flu season. Experts must pick which viruses to include in the vaccine many months in advance in order for vaccine to be produced and delivered on time. (For more information about the vaccine virus selection process visit Selecting the Viruses in the Influenza (Flu) Vaccine.) Because of these factors, there is always the possibility of a less than optimal match between circulating viruses and the viruses in the vaccine.
\nThe production process for some seasonal vaccines also can impact the vaccines effectiveness against certain viruses, like influenza A (H3N2) viruses. Growth in eggs is part of the production process for most seasonal flu vaccines. While all influenza viruses undergo changes when they are grown in eggs, changes in influenza A(H3N2) viruses tend to be more likely to result in antigenic changes compared with changes in other influenza viruses. These so-called \u201cegg-adapted changes\u201d are present in most of the vaccine viruses recommended for use in vaccine production and may reduce their potential effectiveness against circulating influenza viruses. Advances in vaccine production technologies and advanced molecular techniques are being explored as ways to improve flu vaccine effectiveness. Learn more by visiting, Advancements in Influenza Vaccines.
\nIt\u2019s not possible to predict with certainty if a flu vaccine will be a good match for circulating flu viruses because flu viruses are constantly changing. More information about the 2018-2019 flu season and recommended vaccines is available.
\n \n Top of Page \nNo, a flu vaccine cannot cause flu illness. Flu vaccines that are administered with a needle are currently made in two ways: the vaccine is made either with a) flu vaccine viruses that have been killed (inactivated) and are therefore not infectious, or b) with proteins from a flu vaccine virus instead of flu vaccine viruses (which is the case for recombinant influenza vaccine). However, the viruses are attenuated (weakened), and therefore cannot cause flu illness. The weakened viruses are cold-adapted, which means they are designed to only cause infection at the cooler temperatures found within the nose. The viruses cannot infect the lungs or other areas where warmer temperatures exist.
\nWhile a flu vaccine cannot give you flu illness, there are different side effects that may be associated with getting a flu shot or a nasal spray flu vaccine. These side effects are mild and short-lasting, especially when compared to symptoms of bad case of flu.
\nThe flu shot: The viruses in the flu shot are killed (inactivated), so you cannot get the flu from a flu shot. Some minor side effects that may occur are:
\nThe nasal spray: The viruses in the nasal spray vaccine are weakened and do not cause severe symptoms often associated with influenza illness. In children, side effects from the nasal spray may include:
\nIn adults, side effects from the nasal spray vaccine may include:
\nIf these problems occur, they begin soon after vaccination and are mild and short-lived. Almost all people who receive influenza vaccine have no serious problems from it. However, on rare occasions, flu vaccination can cause serious problems, such as severe allergic reactions. People who think that they have been injured by the flu shot can file a claim for compensation from the National Vaccine Injury Compensation Program (VICP).
\nMore information about the safety of flu vaccines is available at Influenza Vaccine Safety.
\n \n Top of Page \nFlu vaccine is produced by private manufacturers, so supply depends on manufacturers. Vaccine manufacturers have projected that they will supply as many as 163 million to 168 million doses of i flu vaccine for the 2018-2019 season.
\nInformation about vaccine supply is available on the CDC\u2019s Vaccine Supply & Distribution web site.
\n \n Top of Page \nPeople 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.
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