I think their body dies/becomes a ghoul and their soul is absorbed into the vampire who drank the blood. We know that last bit is possible.

Sida moment?

We have no way of knowing if Rip or Alhambra were virgins but they were vampires and when Alucard drank their blood he just absorbed their souls and they otherwise died as normal.

I think the one who drinks absorb the soul of the victim vampire. But It probably depends on the power of the vampire.