[nulbyte]

If a billion people need two doses, that's two billion doses. One billion is halfway there, leaving one billion left.

[quietbritishjim]

The parent comment said

> So, about 1 Billion [people] ...

and then

> Out of that 1 Billion are almost done.

To me, they're saying "out of 1 Billion people needing the vaccine, 1 Billion people are almost done".

Whatever the detail of what they meant, "almost done" is an odd way to describe being only (just under) halfway through the process.