I set the perk to activate on completion of the quest MQ101 (when you leave the Helgen Keep cave and are outside for the first time) and added it to the "Player" actor.
For some odd reason the perk doesn't activate at that point but simply is always active.
Here are the perk settings, since I am not allowed to post links apparently:
V Playable
V Hidden
Level: 0
Num: 1
Conditions:
Target: S
Function name: GetQuestCompleted
Function info: Quest: "MQ101"
Comp: ==
Value: 1.00
Perk Entries:
Rank: 1
Priority: 0
Type: Ability
Data 1: PCHealthDrain1
Any help or pointers appreciated!

. Is this possible? And if so, how can I do it?