First of all, keep in mind that I am unable to diagnose you because I am unable to examine you, this forum is for educational purposes.
There are not any reports to my knowledge of reactions of Keppra and the flu-shot. Medications do not need to be stopped to get the flu-shot. The only medications that could cause potential problems would be immunosuppressive medications such as prednisone, cell-cept, cytoxan etc. or immunosuppressive conditions such as HIV/aids. Keppra is perfectly safe to take while getting the flu-shot. Because of your kidney failure problems, the Keppra will stay in your blood longer than in the normal person (66% is secreted in the urine). I would suggest that you get your flu shot. I would also recommend that your doctor check a keppra level, due to your kidney disease.
I hope this has been helpful.
You might want to ask on this forum, too. There aren't any drs., but a lot of experienced/educ. epilepsy patients. They were very friendly and helpful to me.
http://brain.hastypastry.net/forums/forumdisplay.php?f=144