For the 2010-2011 flu season, the U.S. Centers for Disease Control published a fact sheet about inactivated influenza flu shots with the recommendation, "All people 6 months of age and older should get the vaccine." Manufactured with attenuated, or weakened flu viruses, flu shots can't cause an influenza infection. However, some risks are associated with the immunization.
Minor Reactions
The flu shot, like other injections, can cause dizziness and fainting, especially in adolescents, according to Flu.gov. Some individuals complain of redness, swelling, or soreness around the vaccine injection site. Others have a fever, cough, hoarseness, eye redness and itching. These symptoms are usually mild and last only a day or two after the immunization, says the CDC. Notify the health care provider if the problems worsen or persist beyond the second day.
Moderate Effects
It's not uncommon to run a low-grade fever for a day or so after receiving a flu shot. If the fever goes up or persists into the third day, the CDC recommends contacting a physician. An injectable flu vaccine known as Afluria causes high fevers and febrile seizures in children under the age of 8 years, so it shouldn't be used with this age group.
Life-Threatening Problems
Flu shots are grown in eggs, so they can occasionally trigger a life-threatening allergy called anaphylaxis in people allergic to eggs or egg products, says the CDC. Starting anywhere from a few minutes to a few hours after the injection, anaphylaxis involves difficulty breathing, facial swelling, hives, weakness, dizziness and headache. Contact emergency medical services right away for any symptoms of anaphylaxis.
Long-Term Effects
Back in the mid-70s, a number of people developed Guillain-Barre syndrome after receiving a flu shot for a type of swine flu in the U.S. Although there's no evidence that today's inactivated influenza vaccines cause the muscle weakness and paralysis of Guillain-Barre, the CDC recommends using it with caution in individuals who have recovered from Guillain-Barre.
Myths
Many people still believe that flu shots are risky for pregnant women, people with chronic conditions such as diabetes or asthma, elderly individuals and those on immunosuppressants or suffering from immune system disorders such as HIV or AIDS. According to Flu.gov, however, these individuals are at high risk for serious complications if they get the flu and should be immunized as soon as possible.
