By dangers, I mean risk of infected blood that results in transmittal of HIV, Hepatitis, allergic reaction, etc.

Discuss.

I think that either they are not susceptible or long ago found a way to make themselves impervious.

[edit: post was edited to clarify dangers]

And what dangers do blood transfusion recipients face these days? Modern facilities screen blood for issues, such as HIV.

I'm going to say not since poisoning a vampire wouldn't kill them.

I recently learned that though the risk of infection is fairly small (Hep B: .0004%, Hep C/HIV: .00005%), it's impossible to have an entirely reliable screen due to things like (just as an example) when someone contracts HIV it's not detectable in the blood for a certain period of time, and if that person donates blood during that time the disease can still be transmitted and there's some logistical issue with re-checking the blood or something because it can't be saved for that many days anyway.

If it ain't garlic or sunlight, it ain't gonna kill them.

Stake through the heart? Holy Water?

Shooting, drowing, repeating the funeral service or exorcism in some places?

Silver in certain folklore although that usually a werewolf thing.

No because consider how it's ingested, stomach acid would make short work of most blood-borne pathogens.

They're dead, Jim.

Since Vampires are more like living dead than actually alive, no, blood-borne diseases won't kill them.

Would they be afflicted, though? They could be immortal and "live" with something like HIV for the rest of eternity.

We went over this in VTM - Bloodlines. They aren't affected by them, but they can carry them and well, plague bearer.

This is pretty much what I would expect. It wouldn't make much sense for a vampire to suffer the effects of HIV since his immune system is presumably non-functioning anyway.

I'm going with this, since that's what it says in V:tM.

How long can they carry them? Pathogens, viruses and bacteria, need certain conditions in order to live and remain functional, not to mention multiply. I'm not sure an undead creature's body grants those varying conditions. So, it could be the pathogens are rendered dead after a period of time in their bodies and wouldn't be able to transmit anymore to any subsequent victims a vampire might have.

Actually it is a vampire thing. Werewolves didn't have weaknesses in the original lore, you could only avoid them by climbing an ash tree or running into a rye field. Hollywood introduced silver.

And why would diseases affect the undead?

I don't know about hepatitis, but HIV can't survive long outside the body. Unless vampire bodies have the same body temperature and chemistry as ours, I doubt they could even be carriers. Even if they are, the virus certainly wouldn't survive the daytime, when the vampire is indistinguishable from a corpse.

A vampire with an allergy to a specific blood type (not even necessarily related to the one they had when alive) would be believable, though. I'd be surprised if no one's done that yet.

Why do vampires drink blood? The only logical explanation is they can't produce their own, yet they need it to... uh... unlive. So, it's also logical there isn't anything in their undead corpse that would cause allergic reactions of their own, that is, no blood of their own, including no cells of the immune defense.

However, what if a vampire drinks first blood from one person and then drinks blood from a second person with blood incompatible with the first person? Wouldn't that mean those two foreign bloods inside the vampire would react to each other?