What happens if you are a vampire when the Dawnguard quests start?

[Zlobenia]

Does it begin as normal?

[Bansheebutt]

You can get up to the point of recruiting the two Specialists when Isran checks them and you if you're vampires.

Pretty sure he just casually tells you to go get cured before you're allowed to continue any further.

[Zlobenia]

Ok, thanks.

What happens if you become a vampire mid-way through the Dawnguard questline?

[Bansheebutt]

Probably nothing.

That kind of detailing has never been Beth's strongsuit.

[Archnecrotyr]

you can actually complete the whole questline as a Vampire/Vampire Lord. However, you can not use any of the Dawnguard services, such as merchants/followers, unless you go get yourself cured after the end of the questline.

[Randox]

As I remember it, Isran will refuse to talk to you (as will some of the other NPC's I think) if you become a vampire, until you get cured. There might be some quests you can still do in this state, but the final mission can't be started, as far as I know, until you get cured (for the dawnguard side).

[Jonas]

I've actually been a vampire when I started the Dawnguard quest series and he didn't say or do anything. He was just saying the usual stuff and giving me the quests.