If you are level-drained, you need to cast a Restoration spell on the drained character to regain the levels. There are restoration scrolls and temples also offer this service.

Also, there a a couple items within the game that confer Level Drain protection on the character when equipped. These are extremely useful items against Vamps.

Finally, Undead Hunter paladins are naturally immune to level drain ... a darned good reason to play one, given the number of vamps in BG2.

Please help me kill the vampires, I am afraid to go out at night because I keep running into them and Dell,get drained, etc....Thanks...

I think there is little you can do about getting drained. Just have some resurection spells memorised.

Cast Negative Plane Protection (if you have a cleric) - that's made to prevent the old level drain thingy.

Eddith