Basically, to stop someone from being a psy vamp you need to give them energy transplants that should hold them for a while, maybe even a lifetime. Then they won't have to leech from others until their energy transplant is gone.
I have spent my life being an energy vampire. I've come to terms that it is who I am. I was incredibly ill as a child, and still have many of the effects of it. There is no way to become something I am not.
I ground and charge myself so I do not cause illnesses to others. That is the only way I have found a way around this. Stand out in the sun for 10 minutes... that'll help.
As for those of you trying to protect yourselves, put up your shields. Any kind of contact, including phone calls, is all it takes for us to have a connection with your energy.
Please realize that this is not a choice. This is something that just happens... be kind to your psy vamp friends and family if they don't know what they are or how to stop it.