Illinois health and education officials are reminding parents to update their children's immunizations as they head back to school.
Most vaccines are given before a child is 2 years old. But between the ages of 4 and 6, before entering kindergarten, children are due for several booster shots.
Children between 12 and 15 years of age may need booster shots too.
Childhood vaccines prevent diseases and protect children who come into contact with unvaccinated people.
Illinois requires proof of up-to-date immunizations for children entering any grade. Required immunizations include tetanus, measles, rubella, mumps, hepatitis B and chickenpox.