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October Health Tip by Dr. Barrow

Q. I received the flu shot last fall, then I got sick with the stomach flu. My mother told me that the flu shot doesn't stop the kind of flu that causes vomiting and diarrhea. If that's true, why bother getting the flu shot?

A. You are talking about two completely different ailments. The flu shot that is given in the fall is designed to protect you from the most common strains of the influenza virus. Influenza A is the most prevalent type isolated from human infections, and its incidence peaks during the winter months. The flu shot is modified annually and designed to stimulate an antibody response within your body to combat the strains of influenza expected to be most prevalent during a given year. Since it may take up to eight weeks to generate a sufficient antibody response, the shot is usually administered in the fall so patients are maximally protected when flu season finally arrives.

Influenza is highly contagious and enters the body through the airways and infects the nose, throat, bronchial tubes, and lower airways in the lung. It is an acute illness characterized by fever, muscle aches, joint pain, headache, weakness, and respiratory symptoms such as a dry cough and stuffy nose. While the flu can strike virtually anyone and most people recover fully in a few days, elderly people and individuals with underlying lung disease or immune disorders may experience a more serious course. For this reason, it is recommended that these individuals receive the flu vaccine, although it may also be administered to others, depending on the clinical situation. If you have questions about whether you should receive the flu shot, check with your doctor. He or she will be able to address your specific situation and recommend the proper counseling regarding this immunization.

In contrast, the most common cause of viral nausea, vomiting and diarrhea is an enterovirus known as rotavirus. Although it is sometimes euphemistically called the "stomach flu," it is really not a flu virus at all. Like the flu, its incidence also peaks during the winter months, and most people recover in a matter of days. Unlike the flu, however, it is not spread through the air by coughing or sneezing; it is spread by ingesting the virus orally. A rotavirus should not be referred to as the "stomach flu" because it has nothing to do with influenza. This is a very common mistake, however, and I have even heard health care professionals refer to nausea and vomiting as "the stomach flu."

Since these are two distinctly separate conditions, the flu vaccine obviously has no affect on the vomiting and diarrhea associated with a rotavirus infection. Individuals who receive the flu shot in the fall should be protected from the most prevalent strains of influenza that are expected that winter. However, they have no protection against rotavirus, and are fair game to get the "stomach flu" all year long!

For more information:
MU Health Sciences Library