I haven't seen these supplements mentioned on this site so I thought I'd bring them to your attention. I have been using Cold-Fx for a couple of years now and Immunity-Fx for 6 months or so, and find them very helpful at preventing illnesses. Cold-Fx is the "official" cold remedy of the Canadian Hockey Association (I think). Anyway, it's made from a derivative of ginseng and enhances "the immune system's viral-fighting Natural Killer cells and macrophages". You can take it just for colds when you get them or you can take a maintenance dose over the long term, which is what I do, along with Immunity-Fx. They are both pricey, Cold-Fx runs me about $60/month, but I've found them very helpful in preventing illness and in shortening the length of illness when I do get sick. You can get them in small amounts in drugstores, and larger amounts on amazon.com.