According to NBC Chicago:
According to updated guidance on the IDPH website, as of Jan. 18, inmates are now included in Phase 1B.
This puts inmates ahead of persons aged 16 to 64 years old with high-risk medical conditions, which are listed in Phase 1C.
Read it in full at https://www.nbcchicago.com/news/local/illinois-to-vaccinate-inmates-ahead-of-those-with-high-risk-conditions-lawmaker-questions-decision/2418334/