Lots of cultures have varying myths about vampires. Do any of these myths mention a cure that could turn someone back into a (living) human after they were infected?
Most cultures believed that vampires were humans that were raised from the dead or demons, so they didn't look into cures so much as killing them or preventing them from coming back from the dead.
It's unclear whether these were cures, but the closest I have come across were: Exorcisms (but if they believed they were demons, this would more than likely just destroy it rather than make it human) Or in [I believe] Romania where a vampire would be dismembered, burned, and fed to the family members to 'cure?' them. Though this could have also been preventative. I hope this helps.
Unfortunately because myths of vampires vary so widely among cultures and they are so old, it's difficult to find all of the myths surrounding them. Modern interpretations are where you will find most references to cures, but it doesn't seem like that is what you are looking for.