No country is supposed to require a cholera inoculation, although there are exceptions in cases of severe outbreaks. However, I've had demands from uniformed men who clearly want bribes, so I always have something entered on my yellow card with an official looking stamp and signature. Usually, any doctor will write something like "not clinically indicated," stamp and sign it. Since the men demanding bribes generally don't read English, that's all it's ever taken.
There is a new vaccine which is supposed to be better than the old one, but I don't know anything about it since it's approved in Europe (so I hear) but not the States.
Hope that helps.
(El Calafate, headed for El Chalten under drab grey skies)