The condition though, is that the main character has to be/become a vampire. That's all.

Wait, no Yaoi, pls.

Example : Happiness (Oshimi Shuzo)

Rosario to Vampire. I liked it anyway, but the turning into a vampire is waaay later somewhere in the second season. First he turns into a ghoul (berserker vampire thing).
Hellsing...
Trinity Blood. He's not technically a vampire but still...
Vampire Juujikai
Considering that he has to drink her blood to survive in Kaibutsu Oujo it's close, but he is not exactly a vampire... There are real vampires too though.
Was going to recommend Strike the Blood, but I have only watched the anime. I thought that it was quite good though.
Seifuku no Vampiress Lord... well, it's not yaoi...

~4400 manga completed
~1700 ongoing...

Blood Lad
Blood Alone
Hellsing
Hitsuji no Uta
Jitsu wa Watashi wa
Kurozuka
Vampire Juujikai
Vampire Knight this one shoujo plus some (very few) yaoi elements, I doubt you will like it, I personally hate it.

Karin

You are right- Vampire Knight was an anime I despised, even when I first tried watching it at 12. But all the other ones seem good! I have read and loved Hitsuji no Uta and Blood Lad. Thanks for the recs!

Quote from BeThatCat

You are right- Vampire Knight was an anime I despised, even when I first tried watching it at 12. But all the other ones seem good! I have read and loved Hitsuji no Uta and Blood Lad. Thanks for the recs!

Yeah, Vampire Knight was terrible.

Thanks for the recommendations! I actually haven't tried any of these yet, except hellsing