They Lady!
My poor daughter was always sick. She was out of Kindergarten 37 days with everything from Norwalk virus to pink eye. And when she got sick, so did her little sister who would end up with UTIs so they wanted to do surgery on her.
What happens, I start to homeschool and suddenly, they are very rarely sick. They can even go around other sick kids and not get sick.
I think they built up natural immunities.