A somewhat obscure myth, folklore holds that vampires originated with Judas Iscariot, betrayer of Christ. Because Judas had betrayed Christ to the Romans, he and his family were cursed. The Bible holds that Judas committed suicide because of his guilt; suicides in vampire folklore were very likely to come back as vampires, so this may have helped contributed to the belief that vampires originated with Judas.
Also, vampires descended from Judas were usually identified by their red hair. Vampires were scaried by silver, especially a cross or crucifix. This probably came about by the 20 pieces of silver Judas got for betraying Christ.