QUOTE (psychophipps @ Jun 12 2014, 09:42 AM)

I disagree with this. In two quick RL examples:
Two very different examples. The first case is a viral infection. A virus needs to infect cells to procreate, being truly immune to a virus therefore is equivalent to not offering any sustenance (so to speak) to the virus. Either because the cells say "no entry", or because the immune system destroys viral particles and infected cells before the infection takes hold. At most, an immune being could carry viral particles like a dirty syringe does, but with some basic hygiene and a functioning immune system this should not last long.
Note that apart from being immune, there also is the possibility of being infected without ill effect -- not all viruses kill their host cell and if the immune system does not attack the infected cells, nothing bad happens from an infection. But you are still infected. Given that vampires are described as incompatible with any geneware and having hyperactive regenerative capabilities, I think this is not what their immunity does. It's simply that their cells are so alien and/or their body so hostile that viruses are a big "nope".
Bacteria, on the other hand, are independent living organisms, and everybody carries around a whole zoo of them without ill effect. Being immune to them simply means that none of their excretions is harmful to you, and again, that your immune system does not go nuclear on them. So bacteria I can see surviving in a vampire's body, though their regeneration might again object.
Lastly, bear in mind that vampires don't get a blood transfusion, they drink the blood. The human stomach isn't exactly the most friendly environment, especially to bacteria which have adapted to living in the bloodstream.
TL;DR: Depends on how you define "immune", and that's before considering the fact that HMHVV-1 is magic.