The flu shot is an inactivated virus vaccine that is usually given in the arm for adults and children or the thigh with infants. The Centers for Disease Control and Prevention (CDC) recommends a flu shot for anyone who wants to reduce the risk of getting influenza. People who are at high risk for serious complications related to flu and people who live with or care for those people should be vaccinated every year. However, you should be aware of a few potential complications of flu shots before being vaccinated.
Serious Allergic Reactions
In rare cases, administration of the flu shot has caused serious allergic reactions, including serum sickness and anaphylaxis, according to post-marketing studies conducted by Food and Drug Administration-approved flu shot maker CSL Biotherapeutics. Medline Plus notes that serum sickness usually develops one to three weeks after exposure to the flu shot or other triggers. Symptoms can include fever, feeling sick, hives, itching, joint pain, rash, swollen lymph nodes and swelling of the arms, legs and face. In some cases, serum sickness can progress to anaphylaxis.
However, anaphylaxis also can develop on its own, within seconds or minutes of exposure to the flu shot or other substances. Symptoms of this potentially life-threatening condition 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. People with allergies to eggs, antibiotics, natural rubber latex or a history of previous life-threatening allergic reactions to the flu shot should share this information with their health care provider before being vaccinated.
Guillain-Barre Syndrome
Guillain-Barre (pronounced ghee-YAN bah-RAY) syndrome (GBS) is a disease in which a person makes antibodies against her own nerves. The hallmark of GBS is ascending paralysis that begins in the legs and spreads to the trunk of the body and arms. According to the CDC, GBS can last for weeks or months and sometimes causes death. About 1 in 1 million people in the United States develops GBS each year. In 1976, among people who were vaccinated for the swine flu, 1 in 100,000 developed GBS. Between 1992 and 1994, the risk of developing GBS among people vaccinated for seasonal flu was 1.7 times that of people who were not vaccinated; however this figure is controversial because it amounts to less than one extra case per million people vaccinated.
Nervous System Disorders
In addition to GBS, which receives its own warning, the flu shot has also been linked to other kinds of nervous system disorders. Optic Neuritis (ON) consists of eye pain and vision loss that affect one or both eyes. According to a 2008 article in the Journal of Clinical Neuroscience, cases of ON following vaccination with inactivated-virus vaccine were reported in 1996, 1997, 1998 and 2004. The patient in 1996 experienced a resolution of symptoms, only to have them recur with re-vaccination in 1997.
Acute Disseminated Encephalomyelitis (ADE), according to the same article, has been described in adults and children who received several vaccines, including the flu shot. The disease presents with the sudden onset of fever, muscle weakness, increased or decreased reflexes, vision changes, impaired balance, loss of ability to read or write, inability to remember previously known words and other neurological symptoms. In order to be considered vaccine-related, the symptoms must begin within three months of receiving the flu shot. Patients usually recover, however the process may take months or years.
Vascular Disorders
The flu shot has been linked to a kind of inflammation of the arteries known variously as temporal arteritis, giant cell arteritis and cranial nerve arteritis. According to a 2002 article in "Current Opinions in Neurology," the first case was described in 2000. Symptoms include new, severe headaches; visual disturbances; jaw and tongue pain associated with swallowing; and tenderness in the visible arteries across the forehead. In most cases, symptoms resolved with prolonged (up to three years) steroid treatment.
References
- Food and Drug Administration: Influenza Virus Vaccine for the 2009-2010 Season
- Neurological Adverse Events Associated with Vaccination; Current Opinions in Neurology; S Piyasirisilp, T Hemachudha; June 15 2002
- Post-Vaccination Encephalomyelitis: Literature Review and Illustrative Case; Journal of Clinical Neuroscience; W. Huynh, D.J. Cordato, E. Kehdi, L.T. Masters and C. Dedousis; 2008
