Dear Doctor Samson,
My entire family received flu shots before last winter. In the subsequent two months we have had the stomach flu a couple of times and the flu with sore throats and headaches at least once. What good are the flu shots if they don't protect us?
"Flu" is the most commonly misused term in the daily practice of clinical medicine. It is used as a generic diagnostic term. Unfortunately, patients take it as a specific entity. In reality, the term "influenza" means an infection of the respiratory tract by a specific virus. It causes a pneumonia picture with high fever, headache, generalized muscle aches and severe cough. It is not responsive to antibiotics, unless there is a secondary infection by bacteria.
The object of a "flu shot" is to provoke the patient's immune system to make antibodies against the particular influenza organisms in the vaccine. If the strains of influenza in the vaccine are the same ones that are causing a "flu" outbreak, then recipients of the shot are protected. If the influenza virus causing an outbreak was not included in the vaccine used the patient is left vulnerable to the disease. Fortunately, this is not a common occurrence.
To answer your question specifically, the "flus" that you are referring to are not influenza, but various types of viral illnesses. These infectious agents are not included in the influenza vaccine. If the symptoms are gastrointestinal, the condition should be referred to as acute viral gastroenteritis instead of the "stomach flu." It certainly is not wrong to use the generic flu terms as long as everyone understands the difference between true influenza and what is called the "flu" in the non-specific sense.
Whether a patient should receive a "flu shot" is an individual decision that must be made with the help of a person's physician. It demands assessment of the patient's past and current medical status as well as the predicted severity of the coming flu season.
One easily forgets having the "flu" but remembers suffering through a bout of true influenza for a long time.