Side Effects Of The Flu Shot | Belinda Alexi, PharmD | RxEconsult

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Side Effects Of The Flu Shot Category: Viral Infections by - October 16, 2017 | Views: 18953 | Likes: 1 | Comment: 0  

flu shot side effects

The 2017-2018 seasonal flu shot is rapidly approaching full swing as retail pharmacies are pitching it to patients more than ever this season. According to the Centers for Disease Control and Prevention (CDC), the flu shot is recommended for everyone ages six months and older. It is a yearly vaccine administered to protect patients against influenza, or flu. The flu is a dreaded, contagious respiratory illness that ranges from mild to severe illness and may even result in hospitalization and death. Thus, pharmacies promoting the flu shot as quick, easy, and “covered by most insurances” is appealing to patients. The best way to prevent the flu is by getting vaccinated each year. However, many people wonder about the side effects of the flu shot?

Common Side Effects Of The Flu Vaccine

A popular misconception is that the “flu shot gave me the flu.” However, the flu shot cannot cause flu illness. The intramuscular flu vaccine is currently made in two ways: 

1) flu vaccine viruses that have been inactivated, or killed, and are therefore not infectious

2) recombinant vaccine with no flu viruses at all. 

While a flu shot cannot give you flu illness, there are side effects that may be associated with getting a flu shot. The CDC currently does not recommend the nasal spray flu vaccine, thus we will discuss the flu vaccine administered intramuscularly through a needle. Some minor side effects that may occur from a flu shot include:

  • Soreness, pain, redness, or swelling where the shot was given
  • Low-grade fever
  • Muscle aches
  • Headache
  • Fatigue
  • Nausea
  • Fainting

The Fluarix Quadrivalent vaccine listed the most common side effects experienced based on age groups. In adults, the most common side effects were pain at the injection site (36%), muscle aches (16%), headache (16%) and fatigue (16%). In children aged 6 through 17 years, fatigue (20%), muscle aches (18%), headache (16%), and arthralgia (joint pain) (10%) were the most commonly experienced side effects. Lastly, in children aged 3 through 5 years, the most common side effects were drowsiness (17%), irritability (17%), and loss of appetite (16%).

The Fluzone High-Dose, which is the vaccine indicated for patients 65 years and older, was associated with similar common side effects: 

  • Injection-site pain (36%)
  • Muscle aches (21%)
  • Malaise (18%) 
  • Headache (17%)

These side effects occur soon after the vaccination but they are mild and generally last 1-2 days. If symptoms persist for more than 3 days, then consult your doctor. Side effects of the flu shot are less severe than symptoms of a bad case of the flu. 

Severe Side Effects From The Flu Shot

The CDC states that most patients who receive the flu shot do not develop any serious problems. However, in rare cases, a flu shot may cause serious problems. 

Severe allergic reactions

Symptoms of a serious allergic reaction include hives, difficulty breathing, swelling around the eyes or lips, racing heartbeat, dizziness, and a high-grade fever. These symptoms and signs would most likely occur within a few minutes to a few hours after receiving the flu shot. If a patient experiences any of these symptoms, the CDC recommends seeking medical care immediately. If the flu shot is administered at a pharmacy, pharmacists have an emergency kit with them during each vaccination and patients are advised to remain in the pharmacy area for 15 minutes following administration to ensure that the patient is doing well.

Reactions due to an egg allergy

The CDC has released 2017-2018 recommendations for people with an egg allergy. People who only experience hives after eating eggs or egg-containing foods may receive any flu shot formulation appropriate for their age and health status. People who have had a more serious reaction such as lip and tongue swelling, trouble breathing, lightheadedness, or required epinephrine treatment may receive any flu formulation. However, the vaccine should be administered in an inpatient or outpatient medical setting (e.g., clinic, hospital, physician office, etc.) under the supervision of a health care provider who is able to recognize and manage a severe allergic response. Finally, anyone with a severe, life-threatening allergy to any of the vaccine ingredients should not get the flu shot.

Guillain-Barré Syndrome

On very rare occasions, a patient may develop Guillain-Barré Syndrome (GBS). GBS is a disorder in which a person’s own immune system causes damage to nerve cells, leading to muscle weakness and sometimes paralysis. According to the CDC, some studies estimated the risk for GBS after the flu shot to be less than 1 or 2 cases of GBS per one million people vaccinated. There have also been studies that found no association. It should be noted that GBS is more common following the flu illness than following the flu shot.

Extensive research supports the safety of flu shots and hundreds of millions of people in the United States have been safely vaccinated for over 50 years. Each year, the CDC and the Food and Drug Administration (FDA) closely monitor the safety of the flu vaccine. Thus, the flu shot is a safe vaccine with generally minimal side effects.


Centers for Disease Control and Prevention. (2016). Influenza (Flu).

Fluarix Quadrivalent FDA Package Insert

Fluzone High-Dose FDA Package Insert


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