Five percent of all produced COVID-19 vaccine will be held back for emergencies and states will have the option of trading vials within the government's ordering system to get the kind they want.

Those are just a few of the details we're learning about how the vaccine will move around the nation as distribution comes closer, potentially as early as Friday or Saturday.

Paul Ostrowski, who leads supply, production and distribution for the federal government's Operation Warp Speed, walked USA TODAY through the process.

Here's what else we know: Operation Warp Speed, the White House COVID-19 initiative, plans to only ship half of all vaccine available each week. The other half will be held in storage and be released just before the second dose is due for those vaccinated the first time.