I'm going to venture out and hypothesize that it works...my husband got sick on Saturday night. Sunday I tried to get all of my kids to drink grape juice. My 10 year old & my 12 year old & my 5 year old peach drank a cup on Sunday. On Monday, my 5 year old v'ed once. My 7 year old wouldn't drink any-he got sick Monday night, and even still had a bout of d* this morning. Tuesday i got sick with the runs, and i made my 10 year old drink more grape juice, as she was home from school with a fever and throat pain. Tuesday night, my 12 year old got nauseous, but she never v'ed or had the end problems, just a stomach ache and nausea off and on. So my 2 kids who drank at least a cup after being exposed either didn't get sick at all, or got it so mildly that the bodily fluids stayed put! My husband never catches svs, so for him to catch it and have both d and v, it had to be highly contagious.