Flu Shot Side Effects

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A seasonal flu vaccine is administered as a nasal spray or as a shot. A flu shot is an inactivated vaccine most often administered by injecting the vaccine into a patient's arm. The flu vaccine is designed to protect against the three most common influenza viruses of the upcoming season. Flu season may begin as early as October and extend as late as May each year. Although the Centers for Disease Control (CDC) recommend everyone over the age of six months receive a flu shot each year, there are groups of people the CDC deems at greater risk of developing the flu, and thus needing the shot, including pregnant women, those age 65 and older, and people with chronic medical conditions such as diabetes, asthma, and chronic lung disease.[1]

During the 2013-14 flu season, an estimated 135-139 million doses will be available. Most of the 2013-14 vaccine will be trivalent, protecting against A/California/7/2009 (H1N1)pdm09-like virus, A(H3N2) virus antigenic ally like the cell-propagated prototype virus A/Victoria/361/2011, and B/Massachusetts/2/2012-like virus. About 30 million of the does will be quadrivalent, also protecting against B/Brisbane/60/2008-like virus.[2]

Some people receiving flu shots may experience side effects. Possible flu shot side effects include reactions at the injection site, allergic reactions, and drug interactions.


Flickr: USACE Europe District
Flu shot effectiveness 70%-90% effective in those under age 65[3]
Who should get a flu shot Recommended for anyone not wanting to contract the flu, especially those at risk of developing pneumonia, pregnant women, young children, those with chronic conditions such as asthma, diabetes, and heart disease, people over age 65
Uses Prevention of three viruses each year
Common side effects Body aches, low grade fever, redness or swelling where the shot was given, coldlike symptoms, etc.[4]
Who should not take Flu shots Children under 6 months, people allergic to chicken eggs, those who have previously had a severe reaction to the flu shot, etc.[1]
When should flu shots be administered October or November[1]
Disclaimer The information provided by PharmacyDrugGuide is not a substitute for professional medical advice, diagnosis, or treatment. Do not take any action based on the information on this page without consulting a physician.
Author Allison Hughes


Flu Shot Side Effects

Although most people receiving flu shots do not experience serious side effects, adverse reactions may occur. This is true of all drugs, including both prescription and over the counter varieties. The most common side effects of the flu shot include, but are not limited to:[4]

  • Aches
  • Low grade fever
  • Swelling, redness, or soreness in the area where the shot was given

Most side effects only last one or two days after the shot was administered, after which they should subside completely.

Flu Shot Side Effects

Flu Shot Side Effects

Flu Shot Allergic Reactions

Flu shots rarely cause allergic reactions, but some may occur, especially in individuals who have had a previous reaction to a flu shot. Individuals allergic to eggs, primarily chicken eggs, may also have a reaction. This is because the virus for the vaccine are developed in hens' eggs.[4] Symptoms of an allergic reaction include hives, rash, red eyes, and congestion. According to the National Institutes of Health, patients should contact their doctor if they have a severe reaction such as problems breathing or swallowing, swollen face or tongue, wheezing, or feelings of dizziness.[5]

Flu Shot Drug Precautions and Warnings

  • One in every 1 million people who receive a flu shot may develop GBS, also called Guillain-Barre syndrome, which causes nerve damage, weak muscles, and fever.[6]
  • While influenza vaccines are generally well tolerated, combining them with certain medications may reduce the effectiveness of the "shot". Prescription medications that might interact with the flu vaccine include:[7]
    • Drug thinners like warfarin or coumadin
    • Corticosteroids like prednisone and hydrocortisone
    • Cancer chemotherapy agents
    • Medications that suppress the immune system, or immunosuppressants

Also See: Agriflu Side Effects, Fluarix Side Effects, FluLaval Side Effects, Afluria Side Effects, Fluvirin Side Effects, Fluzone High-Dose Side Effects, Free Flu Shots, Tamiflu Coupons, Theraflu Coupons, Vaccines for Children



  1. 1.0 1.1 1.2 http://www.cdc.gov/flu/protect/keyfacts.htm
  2. http://www.cdc.gov/flu/about/season/flu-season-2012-2013.htm
  3. http://www.webmd.com/cold-and-flu/flu-guide/fact-sheet-vaccines
  4. 4.0 4.1 4.2 http://www.nlm.nih.gov/medlineplus/ency/article/002025.htm
  5. http://www.nlm.nih.gov/medlineplus/ency/article/000005.htm
  6. http://www.cdc.gov/flu/about/qa/flushot.htm
  7. http://www.medicinenet.com/influenza_virus_vaccine-vial_intramuscular/page2.htm