Christmas time Year before last my mom and I got so sick with the flu we ended up in the ER,
This past Christmas we took airborne with us, and didnt get sick the entire trip, we did run out of airborne though a few days before we left and we went to walgreens, they said the entire state of florida had run out,
So I would buy lots of it before your trip,
I think you can get sick anytime at WDW but I do believe late November thru december are the months ive seen the most sick people.