How the Flu Shot Works

September 29, 2016
Influenza (the flu) is a serious disease that spreads when the coughs and sneezes of an infected person come into contact with another person’s eyes, nose, or mouth.  Although scientists have developed a vaccine to protect against the flu virus, whether or not to get the flu shot continues to be a topic of debate. Knowing how the flu shot works and its intended benefits will help you and your family make an informed decision the next time you are asked to receive the injection as part of your health care routine.
The flu can cause even the healthiest people to become bedridden. Symptoms include fever, nasal congestion, difficulty breathing, excess phlegm in the sinuses, sore and swollen throat, and cough, and that’s what happens in ‘regular’ cases. Some people experience symptoms so severe that they require hospitalization and in the worst case scenarios can die.
That is why specialists have developed the flu shot. This vaccine not only prevents or reduces the intense flu symptoms but also reduces the spread of infection in communities.

What is the Flu Shot Made Of?

To understand how the flu shot works, it’s important to know what the injection is made of.  The most critical ingredient of the flu shot is the antigen, which is a chemical that is obtained and separated from a deactivated (killed) virus and then mixed with other substances such as stabilizers and preservatives. The virus antigen is what causes symptoms such as runny nose, fever, cough, and body aches. Contrary to popular belief, the patient is not injected with the virus, whether a weakened or dead strain. 
The flu shot can be made in several ways, but the final results always contain a virus antigen. Specialists select three or four strains of the flu virus that are believed to most likely spread and cause illness during the upcoming flu season. This is why vaccines change every year and why doctors encourage their patients to go to a clinic or hospital and get an injection every flu season. 

How the Flu Shot Builds Immunity

The flu shot works by creating an immune response in your body that causes your body to create millions of antibodies and t-cells against the particular strains of influenza virus whose virus antigens are within the injection. 
By getting a flu shot before the flu season goes into full swing, you are giving your body adequate time to build up the antibodies. Therefore, if you are exposed to the same flu strains, your body should have the proper defense mechanisms to fight against it.

The Fight Against Influenza

The benefit of the flu shot is that it protects you from contracting the flu and suffering through its symptoms as well as reducing the chances of it spreading to other people in your community. Although doctors encourage the general public to get flu shots, it is especially important for certain people who are considered to be high risk patients to do so. These include children, the elderly, pregnant women, and others with weakened immune systems.
In the event that you do contract the flu virus, getting the flu shot reduces the symptoms’ intensity to something that is more manageable, which can reduce your chance of being hospitalized. No one likes getting sick, so it’s good news that the flu shot is available for those who want to feel their best during the flu season.


By Dr. Anuwat Keerasuntonpong, Infectious Disease Specialist, Medical Center, Bumrungrad Hospital

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