A PC in our group was off on his own following a recurring villain of our groups. He was paralyzed where he could move, and the vampire bit his neck. The vampire said “now you get to remain 19 (years old) forever” before he left the cave. This was all done in RP.
We found him later, and healed up his bite marks. Our characters know of vampires, specifically only the one that bit him (recurring villain), but don’t really know how vampirism works, because it isn’t a super common thing in this world yet.
My question as the player is:
How does RAW vampirism work in 5e?
Is it a disease that develops over time? Is it something where they have to die and be brought back as a vampire?
If a vampire simply feeds on you (as in drinks some of your blood), you do not turn into a vampire.
If a vampire kills you with its Bite attack (MM, 352):
The target’s hit point maximum is reduced by an amount equal to the necrotic damage taken, and the vampire regains hit points equal to that amount. The reduction lasts until the target finishes a long rest. The target dies if this effect reduces its hit point maximum to 0. A humanoid slain in this way and then buried in the ground rises the following night as a vampire spawn under the vampire’s control.
Ways for a vampire spawn to become a true vampire according to the vampire entry on the Monster Manual:
Most of a vampire’s victims become vampire spawn- ravenous creatures with a vampire’s hunger for blood, but under the control of the vampire that created them. If a true vampire allows a spawn to draw blood from its own body, the spawn transforms into a true vampire no longer under its master’s control. Few vampires are willing to relinquish their control in this manner. Vampire spawn become free-willed when their creator dies.
Or other extraordinary means such as the amber sarcophagus on the Curse of Strahd adventure.
Vampirism is not a disease or a curse, it’s a form of undeath. The only way to cure a vampire would be to kill the creature and then resurrect the corpse.