Police said the officer was driving westbound in the 3600-block of West Madison Avenue with lights and sirens activated when they were struck by a sedan driving south on Central Park Avenue.
The officer was taken to Stroger Hospital in serious condition with blunt trauma to the head, police said. The 17-year-old driver of the sedan suffered some cuts and other injuries and was taken to Mount Sinai Hospital in fair condition.
The driver has been cited for failure to yield to an emergency vehicle, driving without a license and operating an uninsured vehicle.
Major Accidents is investigating the crash, CPD said.