What is flu (influenza) vaccine?

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Influenza (flu) vaccine: Overview

Influenza (flu) is an infection in the lungs and breathing passages. It is caused by the influenza virus. There are different strains, or types, of the flu virus every year. The flu comes on quickly. It can cause a cough, stuffy nose, fever, chills, tiredness, and aches and pains. These symptoms may last for a few weeks. The flu can make you feel very sick, but most of the time it doesn't lead to other problems. But it can cause serious problems in people who are older or who have a long-term illness, such as heart disease or diabetes.

You can help prevent the flu by getting a flu vaccine every year, as soon as it is available. You cannot get the flu from the vaccine. The vaccine prevents most cases of the flu. But even when the vaccine doesn't prevent the flu, it can make symptoms less severe and reduce the chance of problems from the flu.

You may have a slight fever or muscle aches or pains after getting a flu vaccine.

How can you care for yourself after getting a flu vaccine?

  • If you or your child has a sore arm or a slight fever after the vaccine, take an over-the-counter pain medicine, such as acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). Read and follow all instructions on the label. Do not give aspirin to anyone younger than 20. It has been linked to Reye syndrome, a serious illness.
  • Do not take two or more pain medicines at the same time unless the doctor told you to. Many pain medicines have acetaminophen, which is Tylenol. Too much acetaminophen (Tylenol) can be harmful.

How effective is the influenza (seasonal flu) vaccine?

Getting the flu vaccine every year prevents flu infection and its complications in most people. There are different ways to get a flu vaccine. Ask your doctor what is right for you.

Even if a flu vaccine doesn't prevent the flu, it can reduce how severe the flu is and how likely you are to have complications. Getting the flu vaccine can result in fewer days missed from work and fewer visits to a doctor for respiratory infections. It can also reduce the number of people who get complications from the flu, such as pneumonia. And the flu vaccine can help protect the babies of women who got the vaccine while they were pregnant.

Do flu vaccines protect against more than one strain of flu virus?

Flu vaccines are made to work against more than one strain of flu. For example, a trivalent vaccine works against three strains, and a quadrivalent vaccine works against four strains of flu. The U.S. Centers for Disease Control and Prevention (CDC) does not recommend one version over another version.

What are some common questions about the flu vaccine?

The flu (influenza) vaccine saves lives. But sometimes people choose not to get the vaccine because of incorrect information they've heard about the vaccine or the flu.

With conflicting messages out there, it can be hard to know what's true and what to do. The answers to these common questions may help you feel good about deciding to get protected from the flu. And maybe you can use this information to encourage others to get protected too.

Question: Why do I need the vaccine? Getting the flu isn't a big deal, is it?

Answer: At best, the flu is no fun. Even a mild case can cause you to feel bad and miss work or school for a week or more. At worst, flu can become a very serious illness. It's especially risky for some people, including older adults, young children, and people with chronic health conditions like asthma or diabetes. Being pregnant also increases the risk of severe illness. But even otherwise healthy children and adults can get very sick or even die. It's much safer to get the vaccine than to get the flu.

Question: Do I really need to get a flu shot every year? Why isn't one shot enough?

Answer: The protection provided by the flu vaccine fades over time. Plus, flu viruses are always changing. Experts track these changes and update the vaccine every year. With very few exceptions, everyone over the age of 6 months needs to get the flu vaccine each fall. This gives the best protection. If you're pregnant, getting the flu shot also helps to protect your baby until they're old enough to get the vaccine.

Question: What's the point of getting the vaccine if I might still get the flu?

Answer: The flu vaccine prevents many people from getting the flu, but it isn't perfect. It takes about 2 weeks for the shot to be effective, so it's possible to catch the flu before you're fully protected. (And the flu vaccine doesn't prevent colds, "stomach flu," or other viral infections, which may sometimes be mistaken for the flu.) Still, if you do get the flu after getting vaccinated, you're much less likely to get very sick, end up in the hospital, or die from the flu.

Most people who die from the flu didn't get a flu shot. And many of those who die—especially children—were healthy before they got the flu.

Question: Can the flu vaccine make me sick?

Answer: You can't get the flu from the flu vaccine. But any vaccine can make you feel a little ill. For example, you might feel achy or have a slight fever for a few days. This is a sign that your immune system is learning how to fight off the actual flu virus.

Question: It's a hassle and I don't like shots, so I may skip the flu vaccine. Isn't this just a personal choice?

Answer: Nobody loves getting shots. And in fact, some people can get the flu vaccine as a nasal spray instead of a shot. If you're interested, ask your doctor or pharmacist about the nasal flu vaccine.

Whether to get the vaccine or not is a choice that only you can make. But it's about more than just you. Chances are, you're part of a family or community. And this group may include people for whom the flu could be serious or deadly. This might be a new grandchild, a beloved aunt, or a good friend who has a chronic disease. If you get the flu, you could spread it to others. By choosing to get the vaccine, you're helping to protect those you care about as well as yourself.

Who should not get the flu vaccine?

The person who gives the vaccine may tell you not to get it if you:

  • Have a severe allergy to eggs or any part of the vaccine.
  • Have had a severe reaction to a flu vaccine in the past.
  • Have had Guillain-Barré syndrome (GBS).
  • Are sick with a fever. (Get the vaccine when symptoms are gone.)

Who needs the flu (influenza) vaccine?

The flu (influenza) vaccine helps protect against the flu. Flu viruses are always changing, so the flu vaccines are updated every year.

  • All people age 6 months and older need one dose each year.
  • Children younger than 9 years of age may need two doses, depending on when they started getting this yearly vaccine.
  • All adults need one dose each year. It is especially important for:
    • People at higher risk of severe flu.
    • Close contacts of people who are at higher risk. This includes people who live with or care for young children.

It is recommended that adults ages 65 and older get a high-dose flu shot.

It is recommended that those who are pregnant get the flu shot.

Who should get the influenza (flu) vaccine?

Everyone age 6 months or older should get a flu vaccine each year. It lowers the chance of getting and spreading the flu. The vaccine is very important for people who are at high risk for getting other health problems from the flu. This includes:

  • Anyone 50 years of age or older.
  • People who live in a long-term care center, such as a nursing home.
  • All young children.
  • Adults and children 6 months and older who have long-term heart or lung problems, such as asthma.
  • Adults and children 6 months and older who needed medical care or were in a hospital during the past year because of diabetes, chronic kidney disease, or a weak immune system (including HIV or AIDS).
  • People who are pregnant.
  • People who have any condition that can make it hard to breathe or swallow (such as a brain injury or muscle disorders).
  • People who can give the flu to others who are at high risk for problems from the flu. This includes all health care workers and close contacts of people age 50 or older.

Influenza (flu) vaccine: When to call

Call 911 anytime you think you may need emergency care. For example, call if after getting the flu vaccine:

  • You have symptoms of a severe reaction to the flu vaccine. Symptoms of a severe reaction may include:
    • Severe difficulty breathing.
    • Sudden raised, red areas (hives) all over your body.
    • Severe lightheadedness.

Call your doctor now or seek immediate medical care if after getting the flu vaccine:

  • You think you are having a reaction to the flu vaccine, such as a new fever.

Watch closely for changes in your health, and be sure to contact your doctor if you have any problems.

What Difference Could the Flu Vaccine Make?

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The content above contains general health information provided by Healthwise, Incorporated, and reviewed by its medical experts. This content should not replace the advice of your healthcare provider. Not all treatments or services described are offered as services by us. For recommended treatments, please consult your healthcare provider.