But even if you assume the
ICCPR is enforceable in Australia, it is worth reading all of Article 12, which relates to freedom of movement, which I have quoted below. There is sufficient wriggle move in 3) to deal with public health matters, therefore it would come down to some form of adjudication around whether the restrictions were proportionate.
There is also the possibility of derogation, so it's clear that many of the rights are not inviolable, but that seems to relate to the “life of the nation”, not the lives of individuals in the nation. But still further wriggle room.