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Common Misconceptions About Flu Vaccines

on October 9, 2017 - 4:45am

CDC News:

Can a flu shot give you the flu?

No, a flu shot cannot cause flu illness.

Flu vaccines given with a needle are made in two ways:

  • the vaccine is made either with
    • a) flu vaccine viruses that have been ‘inactivated’ and are therefore not infectious; or
    • b) with no flu vaccine viruses at all (which is the case for recombinant influenza vaccine).

The most common side effects from the influenza shot are soreness, redness, tenderness or swelling where the shot was given. Low-grade fever, headache and muscle aches also may occur.

In randomized, blinded studies, where some people get inactivated flu shots and others get salt-water shots, the only differences in symptoms was increased soreness in the arm and redness at the injection site among people who got the flu shot. There were no differences in terms of body aches, fever, cough, runny nose or sore throat.

Are any of the available flu vaccines recommended over the others?

For the 2016-2017 flu season, the Advisory Committee on Immunization Practices (ACIP) recommends annual influenza vaccination for everyone 6 months and older with either the inactivated influenza vaccine (IIV) or the recombinant influenza vaccine (RIV). The nasal spray flu vaccine (live attenuated influenza vaccine or LAIV) should not be used during 2016-2017.

There is no preference for one vaccine over another among the recommended, approved injectable influenza vaccines. There are  many vaccine options to choose from, but the most important thing is for all people 6 months and older to get a flu vaccine every year. If you have questions about which vaccine is best for you, talk to your doctor or other health care professional.

Is it better to get the flu than the flu vaccine?

No. Flu can be a serious disease, particularly among young children, older adults, and people with certain chronic health conditions, such as asthma, heart disease or diabetes. Any flu infection can carry a risk of serious complications, hospitalization or death, even among otherwise healthy children and adults. Therefore, getting vaccinated is a safer choice than risking illness to obtain immune protection.

Do I really need a flu vaccine every year?

Yes. CDC recommends a yearly flu vaccine for just about everyone 6 months and older, even when the viruses the vaccine protects against have not changed from the previous season. The reason for this is that a person’s immune protection from vaccination declines over time, so an annual vaccination is needed to get the “optimal” or best protection against the flu.

Why do some people not feel well after getting the seasonal flu vaccine?

Some people report having mild reactions to flu vaccination. The most common reaction to the flu shot in adults has been soreness, redness or swelling at the spot where the shot was given. This usually lasts less than two days. This initial soreness is most likely the result of the body’s early immune response reacting to a foreign substance entering the body. Other reactions following the flu shot are usually mild and can include a low grade fever and aches. If these reactions occur, they usually begin soon after the shot and last 1-2 days. The most common reactions people have to flu vaccine are considerably less severe than the symptoms caused by actual flu illness.

What about serious reactions to flu vaccine?

Serious allergic reactions to flu vaccines are very rare. If they do occur, it is usually within a few minutes to a few hours after the vaccination. While these reactions can be life-threatening, effective treatments are available.

What about people who get a seasonal flu vaccine and still get sick with flu symptoms?

There are several reasons why someone might get flu symptoms, even after they have been vaccinated against flu. One reason is that some people can become ill from other respiratory viruses besides flu such as rhinoviruses, which are associated with the common cold, cause symptoms similar to flu, and also spread and cause illness during the flu season. The flu vaccine only protects against influenza, not other illnesses.

Another explanation is that it is possible to be exposed to influenza viruses, which cause the flu, shortly before getting vaccinated or during the two-week period after vaccination that it takes the body to develop immune protection. This exposure may result in a person becoming ill with flu before protection from the vaccine takes effect.

A third reason why some people may experience flu like symptoms despite getting vaccinated is that they may have been exposed to a flu virus that is very different from the viruses the vaccine is designed to protect against. The ability of a flu vaccine to protect a person depends largely on the similarity or “match” between the viruses selected to make the vaccine and those spreading and causing illness. There are many different flu viruses that spread and cause illness among people.
The final explanation for experiencing flu symptoms after vaccination is that the flu vaccine can vary in how well it works and some people who get vaccinated may still get sick.


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