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4 Flu Shot Side Effects to Know

In addition to preventive actions to stop the spread of the germs, flu vaccines (also called flu shots) are the best way to protect against the influenza viruses that are expected to be the most common during the upcoming flu season. Flu vaccines do more than just keep you from getting sick with influenza. Flu vaccination also reduces the severity of the illness in case you get the flu. In addition, flu vaccines also lower the risk of flu-related complications for people with certain chronic health conditions like heart diseases, chronic obstructive pulmonary disease (COPD), and other lung diseases.

Flu vaccination has an excellent safety record. Hundreds of millions of Americans have received flu vaccines over the past five decades. However, it is common to develop some minor flu shot side effects. These are temporary and last a few days after getting a flu shot. 

Please continue reading to learn more about the common side effects of the seasonal flu vaccine. 

What is influenza or flu?

Influenza (flu) is a contagious respiratory illness that affects the nose, throat, and lungs. It causes symptoms such as fever, chills, sore throat, cough, common cold symptoms like runny nose and stuffy nose, muscle aches, tiredness, weakness, and headache. Vomiting and diarrhea can happen in some cases, though it is a lot more common in children. To distinguish the flu from the common cold, keep in mind that fever happens to everyone who has the flu, while people with a common cold either have a very low-grade fever or no fever at all. 

Flu is caused by the spread of airborne droplets from people with flu. These droplets happen with coughing, sneezing, and even talking. These droplets from people with flu can land directly in the mouths or noses of surrounding people. Though not as common, you can also get the flu by touching surfaces or objects with the flu virus on it and then touching your nose, mouth, or even eyes. 

When you get infected with a flu virus, your body makes antibodies against that specific strain of the virus. However, influenza viruses keep changing, and new strains keep emerging. 

Every year, scientists research which strains of the flu virus will be most common in the upcoming flu season and include the four most common ones in the flu shot. There are many options to choose from when you get the flu vaccine. Most flu vaccines are given as a shot (injection in the arm), but a nasal spray flu vaccine is also available. The nasal spray vaccine is a live attenuated influenza vaccine for non-pregnant people between the ages of 2 and 49 years. 

What are the CDC recommendations for flu shots?

The Centers for Disease Control and Prevention (CDC) recommends that everyone over the age of 6 months get a routine annual flu vaccination to protect against the common strains of influenza viruses unless they have a contraindication. Babies younger than 6 months of age and people who have previously had a severe allergy to any of the ingredients in flu vaccines should not get the flu shot.

Also, there is a misconception that receiving the flu vaccine may increase your risk of getting sick with COVID-19. Clinical studies have proven that there is no association between flu vaccination and coronavirus infection. The protective benefits of the flu vaccines continue to be endorsed by the CDC and the World Health Organization. 

Can people with an egg allergy get a flu shot?

Most vaccines, including the nasal spray form of the flu vaccine, contain small amounts of egg proteins. However, studies have shown that flu vaccines are unlikely to cause severe allergic reactions in people with egg allergies. It is, therefore, safe for people with egg allergies to get the flu vaccine, including those with a severe egg allergy.

All vaccines are administered in a healthcare setting in which healthcare providers are trained to recognize and treat a severe allergic reaction when it does happen.

How many doses of the flu shot do you need?

Most people need one flu shot every year, including people with chronic illnesses. However, children between 6 months and 8 years of age may need two doses in a single flu season. You are protected about 2 weeks after getting a flu shot since it takes up to two weeks for you to build immunity against the virus.

Can the flu vaccine cause a flu illness?

No, a flu shot cannot cause a flu infection. The vaccine contains an inactivated influenza virus that cannot cause an infection or illness. Even though your body may start to mount an immune response to the flu vaccine, causing you to feel like you are getting sick, this does not mean you have the flu because the flu vaccine contains a dead virus. When you get a flu shot, your body responds to the vaccine by prompting your immune system to make antibodies. These antibodies help to fight off and prevent a flu infection if you are subsequently exposed to flu viruses. These side effects tend to be more common in people who have never received flu vaccination before. 

What are the side effects of flu vaccines?

Possible side effects of the flu vaccine include the following:

Common side effects 

Side effects of the annual flu vaccine are typically mild and go away on their own without any treatment within a few days.

Injection site reaction

Redness, soreness, and swelling can develop as a reaction to the flu vaccine at the place on your arm where you get a flu shot. Talk to your doctor if your sore arm or the redness and swelling do not go away in a few days or if you develop a high fever (more than 101 degrees Fahrenheit). 

Systemic symptoms

Effects of the flu vaccine can also include fever, headache, and muscle aches. Children may develop nausea and vomiting after a flu shot. Some people experience dizziness and fainting after they get a flu shot and other injections. Tell your healthcare provider if you have ever fainted after receiving an injection

Serious side effects 

Very rarely, flu shots can cause more serious adverse effects, such as:

Guillain-Barre syndrome

There may be a possible association between flu vaccination and Guillain-Barre syndrome (GBS), a rare neurologic condition in which the immune system attacks healthy nerve cells. However, the risk of this severe illness happening is very small. You should call your doctor immediately if you develop weakness or tingling in your hands or feet after flu vaccination.

Severe allergic reaction

Rarely do people develop a severe reaction to the flu vaccine. You should seek emergency medical attention if you experience difficulty breathing, wheezing, hoarseness, swelling of the eyes, lips, or throat, skin rash, hives, itching, pale skin, muscle weakness, dizziness, or fainting after a flu shot.



  1. https://www.mayoclinic.org/diseases-conditions/flu/symptoms-causes/syc-20351719

  2. https://www.cdc.gov/flu/prevent/flushot.htm

  3. https://www.cdc.gov/flu/professionals/acip/summary/summary-recommendations.htm

  4. https://www.cdc.gov/vaccines/hcp/vis/vis-statements/flulive.html#:

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  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7798744/

  7. https://www.who.int/teams/global-influenza-programme/vaccines#:~:text=Children%20younger%20than%205%2Dyears,spread%20of%20flu%20to%20others.