According to the Centers for Disease Control and Prevention (CDC), the seasonal flu affects millions of Americans each year. Although in most cases, the flu resolves without treatment, each year approximately 200,000 U.S. residents are hospitalized and 36,000 die from flu-related causes. The CDC counsels people to take time to get a flu vaccine as the best thing they can do to reduce their risk of getting the flu. In healthy adults, the flu vaccine may reduce the risk of flu by 70 to 90 percent. However, educated consumers often want to know about the potential hazards of the flu vaccine.
Injection Site Reactions
The most common side effect of the flu shot is an injection site reaction. In clinical studies by the makers of the FDA-approved flu shot Afluria, the most symptoms were tenderness (60 percent), pain (40 percent), redness (16 percent), swelling (9 percent) and bruising (5 percent). In most cases, these symptoms resolve within 2 days. However, in rare cases, these symptoms are a harbinger of more serious problems, including abscess and cellulitis (infection of the skin). According to MedlinePlus, both conditions are treated with antibiotics. An abscess may also require surgical drainage. This hazard is unique to the flu shot. There is no risk of injection site reactions with FluMist, the intranasal vaccine.
Allergic Reactions
In rare cases, the flu vaccine is associated with serious allergic reactions. According to the FDA-approved prescribing information for each vaccine, these reactions are so infrequent that it's not possible to provide reliable estimates of their prevalence. For example, in the Dec. 4, 2009 edition of "Morbidity & Mortality Weekly Report," the CDC indicated that 16 "serious allergic reactions" and 18 confirmed cases of anaphylaxis had been reported out of approximately 145.1 million administered doses of seasonal and H1N1 flu vaccine. Anaphylaxis is a life-threatening allergic reaction that usually presents with seconds or minutes of exposure to the flu vaccine or other allergens. Symptoms of anaphylaxis, according to Medline Plus, include trouble breathing, hives or skin rashes, hoarse voice, tight throat, vomiting, diarrhea, abdominal pain, low blood pressure, a sense of doom and cardiac arrest. While anaphylaxis usually occurs on repeat exposure to an allergen, an antibiotic used in the preparation of some kinds of flu vaccine, polymyxin, has been known to produce an anaphylaxis-like reaction on first exposure. People with allergies to eggs, antibiotics, natural rubber latex or a history of previous life-threatening allergic reaction to the flu vaccine should share this information with their health care provider before being vaccinated.
Guillain-Barre Syndrome
The autoimmune disease Guillain-Barre Syndrome (GBS) is a recognized hazard of the flu vaccine. First linked to the 1976 swine flu vaccine, flu vaccines have subsequently been reformulated, however concerns remain. According to the CDC, the risk of developing GBS due to the flu vaccine is less than 1 person per million vaccinated. While the risk is low, the disease is serious. Premonitory symptoms of GBS include weakness and tingling in the legs. Symptoms soon increase in both extent and severity-eventually the legs, arms, trunk and head may be paralyzed. When paralysis reaches the level of the diaphragm, the individual will require mechanical ventilation in order to breathe. While the condition is not permanent, recovery is often prolonged (weeks to months) and nearly 1/3 of patients complain of residual weakness three years later.
Optic Neuritis
Optic Neuritis (ON) is a condition characterized by inflammation of the optic nerve. Symptoms include eye pain and vision loss that affects one or both eyes. According to a 2002 article in the "Archives of Neurology," ON following vaccination against seasonal flu was described in 1996, 1997, 1998 and 2004. A link between ON and the flu vaccine was not suspected until the 1996 patient's symptoms resolved, only to recur when she was re-vaccinated in 1997.
Acute Disseminated Encephalomyelitis
According to a 2008 article in the "Journal of Clinical Neuroscience," acute disseminated encephalomyelitis (ADE) is a condition that has been linked to vaccine for flu and several other infections including polio, diptheria and rabies. The name of the disease refers to diffuse inflammation of the brain and spinal cord, which starts abruptly. The symptoms of ADE include sudden onset of fever, muscle weakness, abnormal reflexes, vision loss or changes, loss of balance, loss of ability to read and write, forgetting previously known words and other symptoms. It has been described in both adults and children, although it is more common in children. Like GBS, ADE is not permanent, but recovery usually takes years. The cause of ADE is not well understood, but is believed to based on an abnormal interaction between a person's immune system and the vaccine.
References
- FDA: Influenza Virus Vaccine for the 2009-2010 Season
- • "Current Opinions in Neurology;" Neurological Adverse Events Associated with Vaccination; S. Piyasirisilp, T. Hemachudha; June 15 2002
- "Journal of Clinical Neuroscience;" Post-Vaccination Encephalomyelitis: Literature Review and Illustrative Case; W. Huynh, D.J. Cordato, E. Kehdi, L.T. Masters and C. Dedousis; 2008
