We did the day care thing. Had an at-home nanny for our kid's first eight months in the world and then did day care. Not so much as a sneeze until the baby set foot in a day car facility...then she contracted everything she was inoculated for, as well as an ear infection per month!
Good? Bad? Who knows? She's seems immune to everything now, as she never gets sick but apparently is a "carrier"...my wife gets laid up in bed for days upon contact with the kid!
We went though several facilities for a lot of reasons. Every one of them was investigated thoroughly by us, and when a red flag appeared, BOOM! We took our kid and went in search of another one.
Glad those days are over.