Ask the Doctors by Eve Glazier, M.D. and Elizabeth Ko, M.D

Special Flu Shot for Older People Has More Antigen

Dear Doctor: Our 76-year-old mom is nervous about getting the special Fluzone shot for older people because a neighbor told her it will make her sick. Is that true? What makes flu shots so important?

Dear Reader: Influenza, commonly referred to as the flu, is a seasonal respiratory illness with symptoms similar to those of the common cold. Both illnesses are caused by viruses, but infection with the influenza virus usually results in symptoms that are more severe and longer-lasting than those of a cold. Unlike a cold, which typically comes on gradually, the onset of the flu is often swift. People who get the flu can experience fever, chills, sore throat, cough, lung congestion, body aches and pains, a stuffy and runny nose, and fatigue or exhaustion. Nausea and diarrhea are possible.

Flu season in the United States is concentrated in the fall and winter. Peak activity occurs between December and February. Symptoms show up from one to four days following infection. Depending on the flu strain, as well as the general health of the individual, it can take up to two weeks for the disease to run its course. Most people recover completely. However, at-risk populations with weaker immune systems, such as the elderly, are at increased risk of complications. These can be moderate, such as sinus and ear infections. Severe complications include pneumonia and, more rarely, myocarditis, an inflammation of the heart muscle, or encephalitis, a brain inflammation. In cases where the presence of the influenza virus triggers an extreme inflammatory response, it’s possible for the patient to develop sepsis, a life-threatening infection.

The special flu shot you refer to is called Fluzone High-Dose, a vaccine that contains four times as much antigen as the standard dose. Antigen is the part of the vaccine that causes the body to build up immunity. As we age, our immune response to influenza vaccines declines. The intent of the quadruple dose of influenza antigen is to make up for that reduction in clinical effectiveness. Recent studies have found the high-dose vaccine to be 25% more effective at preventing infection in the elderly. It is also associated with a lower rate of hospitalizations among those who do get the flu. However, it’s also true that side effects to the high-dose vaccine are slightly more frequent than to the standard-dose version.

People getting either type of vaccine may experience side effects including pain, swelling and redness at the injection site, as well as headache, fever, muscle aches and tiredness. Each of these are reported to be mild and temporary, lasting less than a day or two.

Whether your mother overcomes her fear of the high-dose vaccine or opts for the standard-dose variety, we think that the most important thing is for her to get a flu vaccine, no matter which kind, as soon as possible. You should get one, too. In fact, all of our readers should get the flu shot.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.)