discussion on immune system

ch

so I have been wondering if children being exposed while young to germs really helps build their immune system. I am a stay at home mom. we don't go out much, last time she played around her cousins she got roselae or w.e it is (atleast i think. She wasn't diagnosed) but I see and know lots of babies in day care or exposed to more germs get sick more often. we live on a farm, and one of my bf's cousins said she stayed at home with her 3 kids and they rarely got sick and rarely get sick now. I was worried that if she didn't go to somewhere such as daycare she may not build up a strong enough immune system and then be a very sickly teenager or adult, but it kind of put my mind at ease. what are anyone else's thoughts? I love not dealing with the headache of a sick child often but I often ponder if im not building her up enough too