Agree with Bonsoir.
The manager at my DD's pre school has been looking after DC at this nursery for almost 20 years.
Almost every time I see her (3 times a week) she has a bright red runny nose or watery eyes, or has a hacking cough. Quite often, it is all 3.
Now if she hasn't built up enough immunity to avoid most of the coughs/colds in 20 years of daily contact with children, what hope have the rest of us got?
FWIW, I am another who is sick of the constant round of bugs, coughs and colds going round. DD is 3.6, has been at pre school since she was 2, and it is worse this year than I can ever remember it being.
If I wake up one more night to cough so violently that I am heaving, and cannot catch my breath, I will scream and scream. I am heartily sick of being ill, and am silently cursing the bugs and recoil now when I see a child with a face flowing in snot, coughing and spluttering near myself or DD.
I know it is unreasonable to feel this way, and it can't be helped, but I have gone from catching a cough/cold maybe once or twice a year to only being cough/cold free one week in 4!!!! This has been going on for months now. 
I wonder if the mild winter has got something to do with it being particularly bad this year??
Immunity doesn't build up imo...the bugs and germs are just too clever for that.
