The article below, from a few days ago, lists the priority categories per the CDC as to which groups of people will be vaccinated first.
The priorities, in order:
Phase 1a (24 million people)
healthcare personnel with direct exposure to infected persons
residents of long-term care facilities
Phase 1b (49 million people)
people 75 and older
Phase 1c (140 million doses to be distributed)
adults 65 to 74
persons 16-64 with high-risk conditions, such as diabetes or heart disease
persons 16-64 not qualified under Phase 1
Also from article:
"The report and recommendations provided no timelines for when the vaccine doses would be made available, nor the number of doses that would be available during Phase 2 ... Officials have said that most people in the United States should have access to the vaccine by the end of 2021."
I would think it's likely the above categories will be at least fine-tuned or modified as time goes by, depending on multiple factors, but at least we are now getting a picture of what the eventual priority plan is looking like. https://www.upi.com/health_news/2020/12/22/cdc-updates-covid-19-vaccine-priority-recommendations/4811608659416/