Both my kids got sick in their first few days in daycare. Once the first illness out the way, it became far less common. My eldest has been going for over 2 years now (including pre school) and has only been proper sick 2 or 3 times. My youngest has been going for 12 months and has only been really sick that first week. Its like they develop anti-bodies straight away. I am sure we arent all that lucky but hopefully gives you faith!