I get a flu shot every year and I do *not* get sick. My daughter (who lived with us until last August) works in a day care, and brings home everything going around with the kids. I do pretty well avoiding it all.
I only got a flu shot once; in 1995, and that’s because my wife was going through a stem cell transplant for breast cancer. I didn’t care whether I got sick or not, at that time I could risk making her sick.
I’m 49 and I’ll probably start getting flu shots when I’m 55 or so. However, I think diet, exercise, rest and environment are much more important than the shots. Eat plenty of fresh fruit and vegetables, maintain low body fat and keep up your energy, and keep a clean home. We use the expensive high-grade air filters on the furnace, and run a humidifier in the winter. Since we started using the humidifier, our illness rate dropped a lot.