I have never gotten a flu shot either, min, though I may when I get older and more susceptible. I have always had a very healthy immune system when it comes to common illnesses, and believe that allowing your body to run through the cycle of getting sick, especially when you're young and healthy, helps build a stronger immune system. What always troubles me about the flu shot, is that they dont always get the strain right, and the possibility of you still contracting the flu remains pretty high, 40% if you're a healthy adult! Since I rarely get sick, generally once every other year or two, so, I figure, why screw with a good thing?
On the other hand, getting a serious illness, like the measles, can be disastrous to small children and infants, who aren't old enough to get a vaccine, and even though the percentage is small, that you can contract the disease if you've been immunized, there's still a chance, like 7%, that you can still contract it, and so, it's just good preventative medicine to go ahead and vaccinate your children when they are old enough. Why risk an epidemic?
Btw, my percentages are rough and based on a small bit of past research. There may be better numbers someone who has a better medical background, or better, more recent research, may have to share.