...the old school vampires were very zombie-like, but retaining their smarts and maybe some magic power.

I think, considering how dangerous a drug addict can be, while high, or desperate to get a fix, if vampires are real, you definitely can't expect someone to be the same afterwards.

If only Steve has knocked out Tony in the beginning (or if he couldn't be knocked out, break his legs), and then locked him in a cage until they could figure out a cure, a la dealing with friends who are werewolves.