I hope O- finally is of some benefit. Usually signifies bad things. We may be the universal donor, but we can only receive O-. Good luck finding THAT type in a crisis.
She had to have blood once after bad automobile accident (needed four units, iirc) and after a rough delivery. It was always available, which leads me to believe most blood labs like to keep a good supply on the shelves - because it can be given to most everyone for one, and there is no substitute for you guys/gals currently?