Why do people here claim that vampires are real?

It all depends on what you define as a "vampire", like, there are the people who are photosensitive, and some who suffer from a rare dissease that is belived to afect you blood and vitamin levels which can only be fixed by wither getting a blood donation or drinking a ton of V8. And then theres the mythalogical type, those were made up in the mideval times to explain misdeads the kings did and explain as of to why people suffered these disseases.