Influenza is a contagious disease of the respiratory system caused by certain viruses. Often called the flu, influenza is a potentially dangerous disease that, according to the CDC, is responsible for anywhere from 3,000 to 49,000 deaths each year. The CDC recommends that everyone over 6 months of age receive the flu vaccine yearly. The vaccine recipient cannot actually develop influenza as a result of the shot; however, the vaccine does have potential complications and side effects.
Mild Complications
Several mild, localized reactions may occur shortly after receiving the influenza vaccine. The injection site may become puffy, tender, and develop a reddened or mottled appearance. Cold-like symptoms such as a runny nose, sore throat and headache have also been reported, although they are much more common with the nasal spray form of the vaccine. These mild symptoms usually do not require any type of medical intervention, and resolve in 24 to 48 hours.
Moderate Complications
Some vaccine recipients complain of more generalized symptoms that affect the entire body. These include nausea, all-over muscle aches, significant fatigue and a low-grade fever. Such side effects can be treated with over-the-counter medications for symptom relief, and by getting plenty of rest and fluids. These symptoms should dissipate gradually after about 48 hours.
Severe Complications
A severe allergic response to the flu shot is a rare occurrence. Development of acute hives is possible and, according to the Palo Alto Medical Foundation, may be treated with either antihistamines or cortisone injections. Anaphylaxis, another rare side effect, is potentially life-threatening. When it affects the respiratory or cardiovascular systems, it must be treated as a medical emergency.
