Hence, even those vaccinated early on (like presumably international flight crew) will still have to quarantine until such time that enough of the population has been vaccinated so as to not overload the hospital system.
Since the hospital system is actually being underutilised without a vaccine why is this even a remote concern? It would appear that 99% of people in Australia who get the Chinese Strain of Covid 19 seem to be fine and don't end up in hospital. My local hospital has actually been cutting down on casual staff hours due to a lack of things to do and that's with no vaccine.