The Centers for Disease Control and Prevention (CDC) urges Americans to get vaccinated against influenza as the first step toward protecting themselves from the disease. Even if the flu shot does not prevent you from getting the flu, it may reduce the severity of your symptoms and the likelihood of flu-related complications. However, in rare cases, the flu shot is itself associated with complications you may wish to factor into your decision.
Injection Site Reaction
In clinical trial data reported to the U.S. Food and Drug Administration, as many as 60 percent of people reported injection site symptoms such as pain, redness and swelling during the first four days after vaccination. For 1 percent of patients, symptoms were severe enough to interfere with activities of daily living. In rare cases, patients developed injection site complications such as cellulitis, an infection of the skin, or abscess, a localized collection of pus. Both conditions require antibiotics for treatment. Abscesses usually require surgical drainage.
Anaphylaxis
In rare cases, the flu shot can cause a severe, life-threatening allergic reaction known as anaphylaxis. According to the American College of Allergy, Asthma & Immunology, symptoms of anaphylaxis include trouble breathing, hives, tightness of the throat, hoarse voice, nausea, vomiting, abdominal pain, diarrhea, dizziness, low blood pressure, rapid heartbeat and a feeling of doom. Although the first symptoms may simply consist of a "strange feeling," they can quickly progress to cardiac arrest and death. According to manufacturers' product literature, people with allergies to eggs and certain kinds of antibiotics should not receive the flu shot due to the risk of anaphylaxis.
Guillain-Barré Syndrome
Guillain-Barré syndrome (GBS) is an autoimmune disease affecting the peripheral nerves. One in 100,000 people who received the swine flu vaccine in 1976 and one to two in 1 million people who received the seasonal flu shot between 1992 and 1994 developed GBS. Early symptoms of GBS include muscle weakness and tingling, which develops into paralysis. A defining feature of GBS is ascending paralysis, which begins in the lower extremities and progressively affects the upper extremities, face and trunk. According to the CDC, between 5 and 6 percent of people with GBS die despite supportive care. Among those who survive, recovery is prolonged.
Acute Disseminated Encephalomyelitis
Acute disseminated encephalomyelitis (ADE) has been linked to the flu shot as well as vaccines for other diseases, including rabies, polio and diphtheria. According to a 2008 article and case report in the "Journal of Clinical Neuroscience," ADE is more common in children and characteristically onsets within three months of vaccination. Symptoms usually develop suddenly and include fever, muscle weakness, increased or decreased reflexes, vision changes, impaired balance, loss of ability to read or write and the inability to remember previously known words. Although the fever resolves within days or weeks, neurological deficits usually persist for months or years. The precise cause of ADE has not been conclusively established, but it is believed to involve an interaction between the flu shot and a person's immune system.
References
- CDC: CDC Says "Take 3" Actions to Fight the Flu
- FDA: Influenza Virus Vaccine for the 2009-2010 Season
- "Journal of Clinical Neuroscience;" Post-Vaccination Encephalomyelitis: Literature Review and Illustrative Case; W. Huynh, J. Cordato, E. Kehdi, L.T. Masters and C. Dedousis; 2008
