I would imagine it's fairly difficult to get unscheduled time off! However, I know some retail chains have people that work for them on an as-needed basis. Kroger calls them "floaters"; I don't know if it's the same term everywhere, but you get the idea. They go around to different area pharmacies, covering holes in the schedule. I actually think it's a fairly attractive option for mothers who want to be largely stay-at-home, depending on how many stores would need to be covered and if there are babysitting grandparents nearby if the kids aren't in school yet 😉 Depending on where you might work, there are probably people that are on-call for emergency situations. No retail pharmacy is going to want to close for the day because the other pharmacists won't pick up their phone and whomever was on the schedule fell ill!
As far as getting ill is concerned, once again, it depends where you work. I don't know about retail yet, but my boyfriend (WVUPharm2007) worked in a hospital as a tech for about 2 years and ever since, he hasn't gotten majorly ill once, even though I get sick quite often and by all means should be infecting him! He thinks that working in a hospital and being exposed to little bits of illnesses all the time has actually greatly boosted his immunity to tons of diseases. He's been working at a retail pharmacy since August, and he doesn't seem to get more colds or anything like that... though the previous hospital experience could be the reason, I can't really say.
Feel better soon! 😀