I just got some info. from the nurse who runs the health clinic at our school (they will be offering vaccines this year). Apparently there are two types of vaccines. One, the one that can be sprayed nasally, contains a live form of the virus. The other, the shot, does not and is administered to people with immune deficiencies all the time. There is no chance you can actually get the flu from it.
There is more info. on this here:
http://www.cdc.gov/nip/publications/VIS/vis-flu.pdf Knowing this, although it can't hurt to check with your MO anyway, I'd recommend getting the vaccine.
Nelie