Flu Vaccine (Influenza Immunization or Flu Shot)

  • Medical Author:
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

  • Medical Editor: William C. Shiel Jr., MD, FACP, FACR
    William C. Shiel Jr., MD, FACP, FACR

    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Flu Pictures Slideshow: 10 Foods to Eat When You Have the Flu

Quick GuideFlu Pictures Slideshow: 10 Foods to Eat When You Have the Flu

Flu Pictures Slideshow: 10 Foods to Eat When You Have the Flu

What are risks and side effects of the flu vaccine?

Serious side effects of the flu vaccine are uncommon. Side effects of the injection vaccine include soreness at the site of the injection, muscle aching, fever, and feeling unwell. People report less discomfort with the intradermal rather than the intramuscular vaccine. Very rarely, serious allergic reactions have been reported.

Guillain-Barré syndrome (GBS) is an illness characterized by fever, nerve damage, and muscle weakness. In 1976, vaccination with the swine flu vaccine was associated with development of GBS. Studies have been done to evaluate if other flu vaccines were associated with GBS, with only one of the studies showing an association. That single study suggested that one person out of 1 million vaccinated people may be at risk of GBS associated with the vaccine.

The live viruses in the nasal-spray vaccine are weakened so that they do not cause severe symptoms. However, people at high risk for serious complications of the flu (see above) and those with suppressed immune systems (including those taking biologic medications, such as for rheumatoid arthritis) should receive the inactivated rather than the nasal-spray vaccine. Mild symptoms can occur as a side effect of the vaccination. Side effects of the nasal-spray flu vaccine can include runny nose, headache, sore throat, and cough. Children who receive the vaccine may also develop mild fever and muscle aches.

Medically Reviewed by a Doctor on 10/20/2015

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