Erm... body armor in real life is called "bulletproof", but it's more for keeping you from keeling over from getting shot once, maybe twice. It can still be pierced, and even if it isn't, if the round hits in the right place or is a large enough caliber it can break ribs and cause internal bleeding, in addition to the concussion you can get when you are knocked over (don't forget that it will punch the air out of your lungs as well). Maybe in addition to slower healing, you can make armor less effective as well, with a chance for serious effects if you're shot, and perhaps in doing that try to turn people away from the idea that all you need to win in a fight is some armor, robustness, and a mouthful of pills.