This is precisely the reason DS2 will not go to daycare.
He has a horrible immune system and spent most of his first 2 years of his life sick. Not just a cold, enough to be hospitalised a few times. Rotavirus was going around DS1' s daycare and DS2 managed to catch it. People were sending their kids with diarrhea, with no care for the other kids who were catching it.
Unfortunately a common cold in normal kids can make my son incredibly sick for weeks on end.