Influenza flu is a viral respiratory infection that affects millions of people each year. Every year, flu vaccines are developed to protect against the most commonly circulating strains.
Receiving the seasonal flu vaccine is the best way to protect yourself against becoming ill with the flu. But how does the vaccine work? Development of the seasonal flu vaccine actually begins many months ahead of flu season. The viruses used in the vaccine are based on extensive research and surveillance into which strains will be most common during the upcoming season.
Seasonal flu vaccines protect against two types of influenza viruses: influenza A and influenza B. They can also be either trivalent or quadrivalent. The trivalent vaccine protects against three flu viruses: two influenza A viruses and an influenza B virus.
The quadrivalent vaccine protects against the same three viruses as the trivalent vaccine, but it also includes an additional influenza B virus. Once you receive your flu shot, it takes 2 weeks for your body to develop antibodies that provide protection. You can develop the flu along with other respiratory infections, so protecting yourself and others is important. Additionally, influenza viruses are constantly changing.
Because of this, a vaccine from the previous flu season may not protect you through an upcoming flu season. They may give the vaccine at your workplace.
Most adults can have the flu vaccine, but you should avoid it if you have had a serious allergic reaction to a flu vaccine in the past. You may be at risk of an allergic reaction to the flu vaccine injection if you have an egg allergy. This is because some flu vaccines are made using eggs. If you're ill with a high temperature, it's best to wait until you're better before having the flu vaccine.
Flu vaccines help protect against the main types of flu viruses, although there's still a chance you might get flu. If you do get flu after vaccination, it's likely to be milder and not last as long. Having the flu vaccine will also stop you spreading flu to other people who may be more at risk of serious problems from flu. Flu vaccines are very safe. All adult flu vaccines are given by injection into the muscle of the upper arm. It's very rare for anyone to have a serious allergic reaction anaphylaxis to the flu vaccine.
If this does happen, it usually happens within minutes. The person who vaccinates you will be trained to deal with allergic reactions and treat them immediately. See People at Higher Risk of Developing Flu-Related Complications for a full list of age and health factors that confer increased risk.
More information is available at Who Needs a Flu Vaccine. Different influenza flu vaccines are approved for use in people in different age groups. In addition, some vaccines are not recommended for certain groups of people. September and October are generally good times to be vaccinated against flu. Ideally, everyone should be vaccinated by the end of October. However, even if you are not able to get vaccinated until November or later, vaccination is still recommended because flu most commonly peaks in February and significant activity can continue into May.
Find Vaccines. A flu vaccine is needed every year for two reasons. Second, because flu viruses are constantly changing, the composition of flu vaccines is reviewed annually, and vaccines are updated to protect against the viruses that research indicates will be most common during the upcoming flu season.
For the best protection, everyone 6 months and older should get vaccinated annually. It takes about two weeks after vaccination for antibodies to develop in the body and provide protection against influenza virus infection.
Influenza flu vaccine effectiveness VE can vary. During years when the flu vaccine match is good, it is possible to measure substantial benefits from flu vaccination in terms of preventing flu illness and complications. However, the benefits of flu vaccination will still vary, depending on characteristics of the person being vaccinated for example, their health and age , what influenza viruses are circulating that season and, potentially, which type of flu vaccine was used.
For information specific to this season, visit About the Current Flu Season. This is possible for the following reasons:. Some people who get vaccinated may still get sick with flu. However, flu vaccination has been shown in some studies to reduce severity of illness in people who get vaccinated but still get sick. A study showed that flu vaccination reduced deaths, intensive care unit ICU admissions, ICU length of stay, and overall duration of hospitalization among hospitalized adults with flu.
There are many reasons to get an influenza flu vaccine each year. Flu vaccination is the best way to protect yourself and your loved ones against flu and its potentially serious complications. Below is a summary of the benefits of flu vaccination and selected scientific studies that support these benefits.
Despite the many benefits offered by flu vaccination, only about half of Americans get an annual flu vaccine and flu continues to cause millions of illnesses, hundreds of thousands of hospitalizations and tens of thousands of deaths. Many more people could be protected from flu if more people got vaccinated. Even if the effectiveness of the vaccine is reduced against one virus vaccination can still be effective at preventing flu illness caused by the other circulating viruses.
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.
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 used to produce vaccine. The production process for some seasonal vaccines also may impact how well vaccine works against certain viruses, especially influenza A H3N2 viruses.
Growth in eggs is part of the production process for many seasonal flu vaccines. While all influenza viruses undergo changes when they are grown in eggs, changes in influenza A H3N2 viruses are more likely to result in antigenic changes compared with changes in other influenza viruses. A study showed that the vaccine significantly reduces a child's risk of dying of the flu.
Check with your child's doctor. Chronic medical conditions also can increase your risk of influenza complications. Examples include:. Anyone with a chronic medical condition should get the flu vaccine. Also, people living in nursing homes or other long-term care facilities should get the flu vaccine.
There are other groups advised to be cautious about the use of a nasal spray flu vaccine, such as people with certain chronic medical conditions. Check with your doctor to see if you need to be cautious about getting a nasal spray flu vaccine. The flu vaccine can also be delivered by an injection that's usually given in a muscle in the arm. If you're an adult under 65, you may also choose an in-the-skin intradermal vaccine, or you may prefer to have your vaccine delivered using a jet injector device, which uses a high-pressure, narrow stream of fluid to penetrate the skin instead of a needle.
The flu vaccine can't give you the flu. But you might develop flu-like symptoms — despite getting a flu vaccine — for a variety of reasons, including:. How well the flu vaccine works to protect you from the flu can vary.
The flu vaccine is generally more effective among people under 65 years old. Some older people and people with certain medical conditions may develop less immunity after receiving a flu shot.
The vaccine may sometimes be less effective. Even when the vaccine doesn't completely prevent the flu, it may lessen the severity of your illness, and reduce the risk of serious complications and serious illness requiring hospitalization. However, it's especially important to get the flu vaccine this season because the flu and coronavirus disease COVID cause similar symptoms.
Preventing the flu and reducing the severity of flu illness and hospitalizations could also decrease the number of people needing to stay in the hospital. The flu vaccine is your best defense against the flu, but there are additional steps you can take to help protect yourself from the flu and other viruses, including COVID These steps include the following:. If you become sick with the flu, you can also help prevent the spread of the flu by staying home and away from others. Continue staying home until your fever has been gone for at least 24 hours.
Your local health department and the CDC may suggest other precautions to reduce your risk of COVID or the flu if you haven't been fully vaccinated. For example, you may need to practice social distancing physical distancing and stay at least 6 feet 2 meters from others outside your household. You may also need to wear a cloth face mask when around people outside your household when indoors and when outdoors in crowded areas.
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