Behind the flu shot: How does it work and why do you need one?
Jan 18, 2018, 11:29:26 AM CST Jul 30, 2018, 12:10:11 PM CDT

Behind the flu shot: How does it work and why do you need one?

Getting the flu shot every year can help keep your family healthy.


The best offense during a tough flu season is a good defense. You can defend your family from the flu by ensuring everyone in your household gets a flu shot every year.

But why do you have to get a flu shot every year? And how does the flu shot work to prevent the flu? LeAnn Kridelbaugh, M.D., pediatrician with Children’s Health℠ offers these answers to some of the most common flu shot questions.

Why should I get a flu shot?

“Sadly, people die of the flu every year,” says Dr. Kridelbaugh. “If you can protect yourself against a deadly illness, why wouldn’t you?”

Dr. Kridelbaugh says the flu shot is our best defense against the flu and is recommended for every person 6 months of age and older. Your family may especially need a flu shot if someone in your household is at high risk for life-threatening flu complications due to a chronic health condition. Your family member may be at high risk if they are under the age of 5 or over the age 65, or if they have:

Physicians also recommend the flu shot if you or someone in your household is pregnant.

How does the flu shot prevent the flu?

The flu vaccine is designed to stimulate your immune system to make special proteins called antibodies. The standard flu vaccine uses inactivated, “killed” virus particles to cause your body to make antibodies to the flu virus.

After two weeks of receiving the flu vaccination, your body becomes immune to the flu. If live flu viruses enter your body, the antibodies your body made after getting the vaccine will destroy them before they can make you sick.

Does that mean that getting the flu shot can give you the flu? No, explains Dr. Kridelbaugh. Because the vaccine is made with inactivated flu viruses, you cannot get the flu from the flu shot. The viruses are dead and cannot spread or multiply.

Why do I need a flu shot every year?

The antibodies that fight influenza stay at high levels for several months after you receive the vaccine. However, over the course of several months, the body’s immune response from the vaccination begins to decline. As its effectiveness wears off so does a person’s protection from the flu.

“Immunity to the flu doesn’t last long like it does with some other diseases,” says Dr. Kridelbaugh. “We immunize the population every year to try to have continued antibodies in our system that could respond in the event we are exposed to the flu.”

Because flu viruses are constantly changing, the type of flu you may get can change every year, too. Dozens of viruses cause the flu. Each year, the flu shot contains three or four different types of inactivated flu viruses that may not have been in the flu shot the year before.

How effective is the flu shot at preventing the flu?

Each year, companies make a new type of flu vaccine to try to be as effective as possible at preventing the flu. Recommendations from the World Health Organization (WHO) drive the development of the most effective yearly vaccination.

Because dozens of viruses can cause the flu, the WHO looks at what types of flu affected the community the year before. They also look at what strains (types) of flu were most common in Australia and New Zealand.

“Researchers look at what occurred during the flu season in the southern hemisphere, which is in-between the end of our flu season and the start of our next year’s flu season,” says Dr. Kridelbaugh. “It helps them predict and target what strains of the flu they will include in the vaccine.”

Every year, the Centers for Disease Control and Prevention (CDC) evaluates how effective the current flu shot is. The effectiveness can vary, depending on what strains of the flu circulate in the community.

However, even if the vaccine is less effective at preventing one strain of the flu, it may help protect you against another strain of the flu and decrease the severity of your symptoms. That’s why you should get a flu shot even if the vaccine is less effective than normal.

“No one is promising the flu shot is 100 percent effective,” says Dr. Kridelbaugh. “However, it is still the best thing we have to offer you so you don’t get sick at all or are less sick than you would have been without the vaccine.”

Is the flu shot safe for everyone?

Dr. Kridelbaugh says the flu shot is very safe for the general population.

Because of the way the vaccine is made, it contains some egg products. However, new research shows that the flu shot is safe for people with egg allergies. If you have had a reaction to the flu shot before, you should speak to your doctor.

What are other ways I can prevent the flu?

“If you are really trying not to get the flu, you want to avoid crowds of people and avoid people who are sick if at all possible,” says Dr. Kridelbaugh. “If you are sick with the flu, it is recommended that you stay home from work, school and other public places, especially if you have a fever.”

Dr. Kridelbaugh also says frequent hand washing is an important flu prevention strategy. You should wash your hands before you touch your face and before you eat. You should also cover up sneezes and coughs with tissues or by putting your face in the crook of your arm. See more tips for helping your family stay flu free.

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communicable disease, flu, flu season, influenza, immune system, vaccine, virus

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