Due to limited vaccine supplies, not all who become eligible that day will be able to get vaccinated on the first day they are eligible.
Sources tell ABC7 Gov. Pritzker also plans to announce that the state will be adding a bridge phase between Phases 4 and 5 that will be based on science, but offering incremental approaches towards Phase 5.
The step between Phase 4 and 5 will allow for greater capacity limits for bars and restaurants, social gatherings, museums and zoos, etc., depending on whether they are indoors or outdoors. Bars in particular will be allowed 20% standing capacity, but the six-foot social distancing will still be required.
Details of the bridge plan, including when it will begin, will be announced during a Thursday morning press conference by the governor.
SEE ALSO | Chicago Phase 1C vaccine start date set for March 29
Chicago also announced Wednesday that it will expand vaccine eligibility to Phase 1C on March 29.
"I'm excited for it because I've been trying, and I can't get it," said Christopher Hunt, owner of Seek Vintage. "So now that means I may be able to get it."
And along with retail workers, those in hospitality, personal care services, law construction and more are eligible in phase 1C.
Hotel workers are eligible too, at a time the city is poised to reopen conventions.
"Making sure that our staff has access to this vaccine before we start welcoming back more and more guests, I think the two go together," said Michael Jacobson, president and CEO of the Illinois Hotel & Lodging Assoc.
In 1C, Chicagoans 16 to 64 are also eligible, but only if they have chronic health conditions. The state will lift that health requirement for that group on April 12, but it's unclear if the city will, too.
Suburban Cook County is expanding its eligibility starting Monday, March 22, as the county moves to Phase 1B+, which includes people younger than 65 with underlying conditions.
Cook County public health officials said the decision was partly made based on the promise of more vaccine doses on the way.
"We have gotten some indications that supply is going to increase, and yes, that did factor into our decision-making," said Dr. Kiran Joshi, Cook County Dept. of Public Health.
The county said nearly 70% of its seniors have received at least one dose, and that progress is also leading to this expansion announcement.