I don't exactly believe in vampires, but, here's the deal with aging. Over the course of a lifetime, telomeres shorten, when someone gets old they may become hard of hearing or lose their normal vision. This is because those are on the ends of telomeres.
So, there's this substance called telomerase found in cells. It stops certain telomeres or chromosome from shortening, and if they didn't shorten, you could theoretically live forever. Now the Bible does say that God has limited humans to about 121 years of age, so telomerase isn't going to show up in pills or whatever.
But if you think back to the Garden of Eden and to the Tree of Knowledge of Good and Evil, Satan told Eve that if she took the fruit, she could live forever and know what God knows. So I'm thinking those fruits could have had some telomerase. Then since Adam and Eve messed up God limited of lifespans so there you have it.
Kind of got off the subject of vampires, but that's how they could live forever, I guess.

its as intresting a theory as many that iv heard about vamps, now is this a chemicle or purly biological?

Thats incredible. As long as we dont start cutting off each others heads.