score:8
It is the universally accepted opinion that Lord Ruthven character in "The Vampyre" is based on Byron, but the author himself never confirmed this. The story itself was apparently written in 1816, when Byron, his physician Polidori and Mary Percy Shelley with friends stayed at Villa Diodati in Geneva [1]. It was Byron's challenge of writing a ghost story that initiated the writing of both "The Vampyre" and "Frankenstein". Byron himself created the unfinished story known as "Fragment", which Polidori then used to create his own novel - apparently with Byron's knowledge. The story was then written down for the Countess of Breuss, who lived nearby, and from whom the publisher acquired the manuscript later [2].
In 1819 the story was published by Henry Colburn in the New Monthly Magazine - under Byron's name (it seems it was published without first contacting the author). Byron denied his authorship, so later editions removed his name from the front page, although still did not credit Polidori [3].
Thus, the evidence is that by the time Polidori and Byron's relationship indeed soured, the novel was already written, so it is unlikely that it was intended to be a satirize of Byron, and we have no evidence to suggest otherwise. And second - if anything, the "Vampire Fiction" was invented by Byron himself, as it was he who wrote the original fragment which was the basis for Polidori's work.