When flu season arrives it’s time for the annual debate regarding whether or not to get a flu shot. Influenza is a highly contagious, upper respiratory disease with symptoms that can range from mild to deadly. Every flu season brings with it different strains of the flu virus that differ in severity. And the same virus can have different effects on different people. Flu season in the United States begins as early as October and can run as late as May. During this time, flu viruses circulate at increased levels among the U.S. population.

It’s much more serious than a cold: According to the Centers for Disease Control and Prevention (CDC), over the course of 31 seasons from 1976 to 2007, estimates of flu-associated deaths in the United States range from about 3,000 to about 49,000 annually. Of these deaths, 90 percent occur in people 65 years and older. An annual flu vaccine, which can be received in either an injection or nasal spray form, is the best way to reduce your chances of getting seasonal flu and spreading it to others, but the vaccines aren’t for everyone. To understand why, one must first understand the nature of the vaccines themselves.

Those Who Can, Should

The CDC notes that flu vaccines are administered to cause the body to develop antibodies that protect against infection within about two weeks of vaccination. That is to say, flu vaccines are not 100 percent effective at preventing the flu. Each year's flu vaccine protects against the strain of flu that experts find will be most common in the current season.

Traditional seasonal flu vaccines (trivalent vaccines) provide protection from three strains of the flu virus, according to the CDC.

·         An influenza A (H1N1) virus

·         An influenza A (H3N2) virus

·         An influenza B virus