Behind the flu shot: How does it work and why do you need one?
Published November 2018
Updated November 14, 2018
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The best offense during a tough flu season is a good defense. You can protect 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? Preeti Sharma, M.D., pulmonologist at Children’s Health℠ and Assistant Professor at UT Southwestern answers seven common flu shot questions.

Why should I get a flu shot?
The flu shot 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:

  • Asthma
  • Diabetes
  • Heart disease
  • Metabolic conditions
  • Neurologic conditions
  • Neuromuscular disorders
  • Chronic lung diseases
  • Physicians also recommend the flu shot if you or someone in your household is pregnant.

When should you get a flu shot?
Typically, it’s best to get the flu shot starting in early October and before the end of November. It can take up to two weeks for the antibodies to develop after the vaccine is administered, so it’s most effective to get the flu shot before flu season hits. For the 2018-2019 flu season, doctors recommend to get the flu shot sooner if possible, as some early cases of the flu are occurring.

If you miss the early window of getting the flu vaccine, Dr. Sharma advises it’s better late than never. Some flu seasons stretch out for months. Getting the vaccine at any time will help reduce your family’s risk of getting sick and reduce the change for flu related complications.

How does the flu shot work?
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 has enhanced immunity to the flu. If live flu viruses enter your body, the antibodies your body made after getting the vaccine will help destroy them before they can make you sick. This prevents you from getting the flu or can make a case of the flu less severe.

Does that mean that getting the flu shot can give you the flu? No, says Dr. Sharma. 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.

How often should you get the flu shot?
It’s important to get the 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.

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.

Worried that getting the flu shot every year might reduce its effectiveness? A 2018 study supports that an annual vaccination is the best way to protect against the flu, and in no way makes the shot less effective.

Is the flu shot effective?
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. By looking at those factors, researchers can help predict and target what strains of the flu to include in the vaccine.

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

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.

Is it safe to get the flu shot?
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.

As with any medical treatment, the flu shot may cause some side effects. Most are mild and will last only a few days.

What are other ways I can prevent the flu?
To avoid contracting the flu, it’s best to avoid crowds of people and people who are sick if possible. 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.

Frequent and proper hand washing is also an important flu prevention strategy. Wash your hands with soap and warm water for 20 seconds, especially before eating or touching your face. 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.

If you or your child needs a flu shot, we recommend visiting your primary care physician. See more flu shot locations in Dallas here.

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Article originally posted by Children’s Health.

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