On Friday we leave for Disney World!

Last Christmas when we went to Disney I got REALLY sick on our last day.

Flying back and being (miserably) sick was NOT fun. I guess all the flying, environmental changes, long days, etc. caught up with me.
I'd like to start taking something now so hopefully I can prevent getting a cold. Anyone know of any good remedies that prevents you from getting a cold? I'm thinking about getting some Vitamin C tablets.