When I was 16-17 maybe? In my country it's mandatory to receive vaccinations from age 4 to 14 (IIRC) and it's administered by the school health care (So the school nurse), but I missed the last one and it was a royal pain in the ass to get it afterwards.
I haven't vaccinated myself for anything since. I have not felt that I needed a flu vaccination because I'm not in one of the risk groups for that particular disease.
However, I do encourage people in risk groups to get vaccinated, as I personally saw one of my bosses (at the time) fall ill in swine flu (H1N1) and nearly die from it. And he was, what, 50-60 something?
He was in critical status for close to a month and in the hospital for another 3-4 months and wasn't fully recovered from it even when he got back home again. It is very likely that he got some lasting damage from it (Stress on the heart, for certain).
So yeah, get vaccinated. Yes, you should study what that actually entails, with that particular vaccine.
But in 99% of the cases it's going to be the lesser of two evils or not even remotely evil at all.
Edit - Had to make a correction, since those initial time scales were way off. My memory is not the most reliable so I took me longer than writing the post to remember the details.