Assuming you mean 1b have had at least 1 dose, I don't think that's true. If 1b doses have been given, and ~300m people have had 2 doses (i.e. consumed 600m doses), that surely means ~400m doses were left. So a total of 700m people have had one or more doses.
26.16% of that are children. (https://www.statista.com/statistics/271315/age-distribution-...)
So, about 1 Billion require 2 doses of vaccination.
Out of that 1 Billion are almost done.
A long way to go, but an impressive journey so far.