In Dead Rising 2 for the Xbox 360, you will need to save Katy three times with Zombrex to keep her alive. But trying to find them can be difficult, and there are actually four in total scattered about Fortune City. If you're having trouble finding them, check out this video. In it you will get all the locations for each Zombrex vial.
Have an iPhone? Check out all 200+ new features coming in iOS 13.