SPRINGFIELD, Ill. — Illinois health and education officials are reminding parents to update their children's immunizations before they head back to school.

New Illinois Department of Public Health rules require students entering sixth and ninth grades this year to show proof of receiving the Tdap (TEE'-dap) vaccine. That's a booster shot against tetanus, diphtheria and pertussis, commonly known as whooping cough.

Health department Director Dr. LaMar Hasbrouck says the requirement coincides with an increase in whooping cough cases in Illinois. Vaccines prevent diseases and protect children who come into contact with unvaccinated people.