Existem vampiros no Potterverse?

Em Príncipe Mestiço na festa de feriado do Slughorn, Sanguini, o vampiro, é um convidado.

‘Harry, I’d like you to meet Eldred Worple, an old student of mine, author of Blood Brothers: My Life Amongst the Vampires – and, of course, his friend Sanguini.’

Worple, who was a small, bespectacled man, grabbed Harry’s hand and shook it enthusiastically; the vampire Sanguini, who was tall and emaciated with dark shadows under his eyes, merely nodded.

_{Half-Blood Prince - page 295 - Bloomsbury - chapter 15, The Unbreakable Vow}

Eu particularmente gosto disso:

'Sanguini, stay here!’ added Worple, suddenly stern, for the vampire had been edging towards the nearby group of girls, a rather hungry look in his eye. ‘Here, have a pasty,’ said Worple, seizing one from a passing elf and stuffing it into Sanguini’s hand before turning his attention back to Harry.

_{Half-Blood Prince - page 296 - Bloomsbury - chapter 15, The Unbreakable Vow}

Duas provas do livro 3:

1. No capítulo três, ao ver uma foto de Sirius no jornal, a reação de Harry é:

   Harry had never met a vampire, but he had seen pictures of them in his Defense Against the Dark Arts classes, and Black, with his waxy white skin, looked just like one.

  

Alguns dizem que Lupin pode ter feito isso como retribuição;)

Eu descobri que há uma menção bastante clara de Vampiros antes do Slug Club. Hagrid explica como ele teve que livrar-se do pessoal do Ministério que estava vigiando ele e Madame Maxime antes que eles pudessem viajar em segurança para a terra dos gigantes em Harry Potter e a Ordem da Fênix, capítulo 20, e tem este snippet:

‘We chanced a bit o' magic after that an' it wasn't a bad journey. Ran inter a couple o' mad trolls on the Polish border an' I had a sligh' disagreement with a vampire in a pub in Minsk, bu' apart from tha' couldn't'a bin smoother.’

A citação de Sly é a melhor no mundo canon que temos. Recentemente, no entanto, uma atualização no pottermore adicionou mais sobre vampiros.

Looking back through my earliest notebooks, however, I found that on my very earliest list of staff, there was a subjectless vampire teacher I had forgotten, called 'Trocar'.

e ela também confirma por qualquer autenticidade duvidosa Sanguini,

Aside from passing mentions, therefore, the only vampire whom Harry meets in the books is Sanguini in Half-Blood Prince, who makes a faintly comic appearance at a party.

Vampiro / Pottermore

Sim. Vampiros existem, como vemos nas outras respostas, mas há um ponto não mencionado: Sabemos a razão pela qual os Vampiros não aparecem mais.

De acordo com a pesquisa exaustiva do Ibid sobre o cânone de Harry Potter, há uma cura para as mordidas de Vampiro.

The following is a (non-exhaustive) selection of new canon that we can learn from the W.O.M.B.A.T.s. The list focuses on canon exclusive to the Wombats. Much other content merely corroborates things we know from interviews, pottermore writings, the Daily Prophet newsletters, and the famous wizard cards. (The WOMBATs are actually the only source that includes info found on the PoA FW cards.)

....There are no female centaurs and no male veela. Vampire bites are curable nowadays, and ghosts can cause movements in liquids and gases.

Source: The Rowling Library, Ibid, What The Wombats Are And What They Mean For Canon

Eles nunca são mostrados nos filmes (até onde sei), mas no livro de Harry Potter e o Enigma do Príncipe, enquanto Harry está em uma das festas do "Slug Club" do Professor Slughorn, há um vampiro presente.