Originally Posted by JGordon

Definitely, though flu scientists have gotten very good at predicting flu strains based on reported cases, and most years the flu vaccine is a pretty good match for the strains that are floating around. Though there is always the danger of a new strain (like H1N1 last year) popping up that nobody has ever seen before.

Forgot to mention that if you've ever had a flu vaccine in the past and didn't have a severe adverse reaction then, your chances of having a reaction to the vaccine in the future are way less than 1 in a million as the vaccines are always made out of the same type of stuff.