Are vaccinations generally required at daycare centers?

I have a son, 8 weeks old, who will be in daycare soon. I just had my flu shot for him (I have never had one before now). I would feel horrible if I gave him the flu…
My question is this: will the other children at his daycare be required to have vaccines/shots preventing the spread of illness? I would like them to. If it’s not common for a daycare to require this of the children there, will it be hard for me to find a center that does? I really do not want my son around un-vaccinated children (b/c he is so young he hasn’t had all his vaccines yet——I do not want him around older children who could give him a serious illness). I am particularly adamant about this because he has already been ill and it was a terrible time for me. The first 2 weeks of his life were spent in the NICU…