I too never got sick when I worked as a Pharmacist. But I was smart enough to know better than jump to conclusions. The fact that I was in my mid-twenties didn't hurt, nor did the fact that I was around sick people year-round and probably had a pretty healthy immune system built up.
Same here. As a rule I don't get sick very often, depite people coming in everyday for their antibiotics. Although I seem to do my best to weaken my body by only getting 4-5 hours of sleep a night before heading in to 11 hours of work.