I played a 2E Dark Sun campaign and one of my fellow players was unwillingly turned into a vampire. The DM ruled that he was always sick during the day if he was outside--mechanically it was something like -2 to all d20 rolls.
Also, it was amazing how many attacks knocked off his hood.

He rigged up something to keep it on tight, but the DM ruled he had a penalty to initiative (and Search/Perception or whatever we used in 2E).
Whenever he was exposed to the sun he took increasing damage (1, 2, 4, 8, 16, 32, etc). I think being Stunned is much worse.
Ah, good times.