I'm not sure how exactly you'd take it into account in terms of cartridge selection. The only round I know of that reliably penetrates SOME body armor is the FN5.7 and then only with rounds that are a wee bit tough to get for us civvies. Nice gun, awesome round, a little big to conceal and very pricey.
The best way to take it into account is to practice the classic "Failure to Stop" drill.
Still happily answering to the call-sign Peetza.
You do not HAVE a soul. You ARE a soul. You HAVE a body.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.