By Dr. Mercola

The U.S. Centers for Disease Control and Prevention (CDC) recommends a yearly flu vaccine as "the first and most important step in protecting against flu viruses."

This advice applies to everyone 6 months of age and older, and the CDC stresses that you "should get a flu vaccine as soon as [they] are available."

With a promotion this strong, you might assume that getting a flu shot is a "sure thing" to protect you from all flu-like illness this year, but actually it's not.

Not even close.

During the "flu season," doctors and patients alike often attribute respiratory illness to "the flu" or influenza viruses when they most of the time flu-like symtpoms are actually associated with other types of viruses and bacteria.

The only way to know for sure what type of virus or bacteria is causing flu-ike symptoms is to have it lab confirmed.

The seasonal influenza vaccine only contains three strains of type A or type B influenza, which U.S. and WHO health officials select each year as the most likely influenza strains that will circulate around the world.

There are many influenza strains and most cases of flu-like illness that occur in the U.S. during a typical flu season are not associated with type A or type B influenza strains.

So, it is important to remember that, when you feel like you have the "flu," you can't automatically assume that your flu symptoms are caused by type A or type B influenza strains included in the seasonal flu vaccine. Also, people who do get a flu shot every year cannot automatically assume they will not get sick with either type A or type B influenza or another respiratory iillness that looks and feels like influenza.