The risk of having close contact with someone when you are on a prednisone prescription is to you, not to the other person. Taking prednisone can make the person taking it more prone to getting infections. I haven't seen any risks to the partner noted in the literature, just risks to the person taking the medication. How long will the prescription run? Is it just a 5-day prescription or something longer?
I would not be concerned about someone taking prednisone having sex and passing it to their partner. Are you allergic to prednisone for why you are asking?