Daycare kids get few illnesses in elementary school and build stronger immunity against future bugs.

Canadian researchers studied more than twelve hundred families with newborns in 1998. Mothers reported whether their children went to a large or small child-care facility, or whether they were cared for at home.

For eight years the children were followed and tracked to see how often they developed respiratory tract, ear or GI infections. The kids who attended large centers before age 2 ½ had more respiratory bugs and ear infections during early preschool. But they also got less of those illnesses during early elementary school versus the kids who stayed at home.

Only the kids who attended large centers enjoyed future immunity. Those in facilities with just 3 to 8 kids, didn't.

Daycare didn't affect the risk of stomach bugs at all.