John Polidori was Lord Byron's physician and the author of The Vampyre. Both Polidori and Byron were on vacation with Mary Shelley at Lake Geneva when she got the idea for her story of Frankenstein. While trapped inside due to rainy weather, they all threw around ideas for the creation of their own ghost stories after reading other stories. Byron began to write a story, and Polidori took his ideas and formed the novel. Polidori gave him credit in the first edition that was published, but Byron claimed that he was not the author. The creation of The Vampire was inspired on the same trip as Frankenstein was, and it was first published the same year as Frankenstein. Though Frankenstein arguably became a much more influential work in the field of science fiction and literature, Polidori's work being contemporary to Shelley's helped to contribute to the popularization of the genre.
Source: “The Vampyre by John Polidori.” British Library, https://www.bl.uk/collection-items/the-vampyre-by-john-polidoric.