You need Health to be a formidable Vampire. The more Health you have the more damage you can take before needing to heal. You need at least 20 Health to fight a player Vampire. Health gradually recharges over time and recovers completely when you gain a level. Allocating new points to Health give you them right away. It takes 1 point to increase this Skill.
You can spend Blood at the Crypt to recover instantly.