That's true, you can't get the flu from the flu shot. Some people have mild side effects from the shot that mimic the flu so they think they got the flu from the shot.

The CDC (Center for Disease Control) in Atlanta determines the makeup of the flu vaccine every year. You have seen the word trivalent associated with the vaccine, it simply means that it is a 3-strain vaccine. The CDC determines the three most likely strains of flu likely to cause problems and the vaccines are produced to combat those three strains.

If the strain floating around is not one of the three selected for the vaccine then the vaccine will do you no good.

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