The red, or highest risk, category was removed, and the quarantine requirement was cut from 14 days to 10.

States other than Illinois, plus Puerto Rico, are now assigned orange or yellow designations.

"Orange" designates states with more than 15 daily cases per 100,000 residents, and requires either a 10-day quarantine or a negative test result no more than 72 hours before arrival in Illinois.

"Yellow" indicates states with 15 or fewer daily cases per 100,000 residents and requires neither a quarantine nor a pre-arrival negative test.

The only state currently meeting the "yellow" guideline is Hawaii.

The advisory advises against all travel to "orange" states and against non-essential travel to "yellow" states. It also re-emphasizes the importance of wearing masks and social distancing.

"We've made this change to come more in line with updated CDC (Centers for Disease Control and Prevention) guidance related to travel and also in recognition that testing is available in more settings," Dr. Allison Arwady, commissioner of the Chicago Department of Public Health, said in a livestreamed news conference announcing the updates.

Still, Arwady said, "the top line is to please avoid all travel if possible."

Arwady reported improved numbers for the city in several categories:

• New cases per day (about 1,000, down from a November peak of about 2,400 a day, but still above the 400 per day seen in the summer);
• Positivity (10.3%, below the state's 12% benchmark for easing various restrictions, but above the city's target of 5%);
• Deaths per day (13, almost half of the 24 reported in early December, but above the low point of 3-4).

Gallery: COVID-19 vaccine administered at Region hospitals