text: inactive (dead) virus that stimulates the immune system to produce antibodies ( with the immune system 'primed' it will destroy the flu virus before it has   had a chance to reproduce and spread therefore either preventing the flu or making it much less severe)\n\nSINCE THE VIRUS IS INACTIVE IT CAN NOT CAUSE THE FLU but your body will produce antibodies and in some people that process can cause a VERY MILD reaction ( slight fever and the 'blahs' ) a few people ( 1 in a few million have had an allergic reaction - but these same people with the flu would definitely DIE fast - as soon as the virus started reproducing ! ) GET THE SHOT !