NO

However, certain characters were introduced in other "Chicago" series, specifically, Chicago Fire.

Primarily these are:

Antonio Dawson, portrayed by Jon Seda, is a fictional character in the Chicago franchise and is a main character in Chicago P.D. and Chicago Justice. He was introduced as a recurring character on Chicago Fire before the spin-off Chicago P.D. was created.

Detective Jay Halstead previously appeared on Chicago Fire as an undercover cop assigned to take down a local mobster-cum-thug. He requests a transfer to the Intelligence Unit after the assignment ended with him getting shot but successfully arresting the mobster. Chicago P.D. begins a month following his transfer.

Hank Voight, This character was first seen in Chicago Fire as an antagonist. Voight's ruthless methods cause friction with Lieutenant Matthew Casey, a firefighter at the nearby Firehouse 51

Erin Lindsay, The character was first introduced in Chicago Fire, as one of the Chicago PD detectives the firefighters of 51 regularly come into contact with.

These characters and others have relationships with other characters that spread throught the various Chicago series such as Chicago Fire and Chicago Med.