The flu shot this year is three strains of the flu, and they are all inactive aka dead. As always. Nobody actually gets sick from the shot, but some people do start to feel sick. It only takes two weeks to build up complete immunization, so for a few days the body starts working overtime to kill the dead flu strains that were injected, and that can make one feel weak, a little achy, and sometimes even develop a mild fever. It's just the body fighting it off, not the actual kick in the teeth that influenza likes to be.
I had mine last year while on SD and test and had no negative reaction, just felt a little crappy for a couple days, but nothing severe in the slightest.