 The new school year will be here before you know it, so this might be a good time to get your child a medical checkup. Experts say the late summer doctor visit can help make sure children are up to date on their immunizations. Vaccines all work differently, but they help the body's immune system learn to fight germs. And it can take weeks for that protection to develop. When school age kids get their vaccinations on time and before they go to school, they're less likely to catch things at school.