I do not take any flu shots or vaccines. My doctors don't mention it, and I don't bring it up. I know those with immune problems are the most likely to have reactions to them, and I'd quite frankly prefer dealing with the flu over dealing with an unknown reaction to something messing up my immune system in an unnatural way. The closest personal experience I have is when I was getting allergy shots. This was when I was still high functioning with my CFS. After every shot I would go home and immediately sleep for 18 hours straight or longer, waking only briefly to get water and food before barely making it back to bed, fully exhausted, and instantly falling asleep again. Each time I thought it was a fluke until I noticed, hey, it's only happening after I get an allergy shot. I asked the allergy doctor about it and she said there was no chance there was any connection. I kept getting the shots, week after week, and it would always knock me out for two days. The doctor insisted it wasn't the shots. Finally I just said "no more" and that was that - coincidentally, the 18 hour blocks of sleep stopped happening after that! For vaccines it isn't jsut the dead or live virus they give you....it also includes certain chemicals meant to basically stimulate your immune system to pay attention to it, or at least that's my understanding. So it manipulates your immune system in an unnatural way. If you already have a dysfunctional immune system, it's little wonder that it doesn't respond well to these kinds of things.