I learned in Biol 100 that once you have a virus, you never get the same one again. When you get a cold, it's a new virus, not the same one you've ever had before. How this applies to Foot & Mouth, I don't know, but I'd guess it makes it a one-time shot. At least I hope so! What confuses me is that apparently people continue to harbor the chicken pox virus for the rest of their lives, and sometimes it comes back as shingles...but not chicken pox. Seems kinda odd, but there you go.