In the US this is expressly forbidden by the Americans with Disabilities Act (ADA). It would surprise me a lot if stuff in AU is even worse than here, since for the most part it is pretty bad here. Anyway, contact a labor lawyer.
Australia is often much worse, in this sort of area, than people think. Despite a superficial similarity with UK culture and laws (which already are much weaker than the Western European average, but anyway), they are actually pretty wild.
Wikipedia says about discrimination, not about medical records.
Also, it is legal to fire people based on their vaccination status which is obviously a medical record.