I reckon that this question could be answered (in one possible way) by modeling an answer on examples based on natural history.
As vampires supposedly have a physiology that is dependent on the infusion of living blood from a host then we could possibly look to the examples of the mosquito, flea and (vampire) bat.
The two former organisms encounter viruses and pathogens that may be deadly to any species specific host, in fact they (mosquito and flea) are noted and widely responsible for spreading contagions and diseases such as malaria and plague. However, these organisms suffer no ill effects from encountering and carrying these diseases.
So, if we base a logical presumption on the basis that vampires are indeed significantly different in physiology to that of humans, then they would probably not suffer any ill effect when encountering a human disease that is transmissble by ingesting blood.
However, if we look to the example of the vampire bat, then we have a different proposition. As vampires are seen as a form of human, or at least based on a human physiology, then their genetic make-up must be similar (to a lesser or greater degree) If this is the case, then as with vampire bats, they would be at risk of contracting some diseases. For instance, rabies is a transgenic disease that is communicable between most (if not all) mammalian species. Although with this said, a species that is so specialised in regards to its feeding requirements may well form some kind of immunity to communicable disease through a process of natural genetic evolution.
Anyway, this is just one possible idea, but if we assume that vampires are indeed the undead then we would be fairly safe to assume that diseases that affect the living would be of no consequence to a (re-animated) corpse.
That is a very thoughtfull answer thanks. Anyone have anything to add or dieagree?