It is lack of vaccine availability, due to a combination of bad luck and federal government incompetence. We invested everything in Astra Zeneca and a locally produced mRNA vaccine. Unfortunately the locally developed vaccine, while highly effective, had the unfortunate side effect of making recipients test positive to HIV (I'm not making this up). And media coverage of clotting issues with AZ has left boomers demanding they get Pfizer instead (hitherto restricted to under-50s).

Australia may have won with COVID eradication and containment, but it is completely flubbing vaccination. Only about 4 per cent of the population is fully vaccinated as of today (including me, as it happens). Borders won't be reopening anytime soon, which means international travel to and and out of here is still a long way off. Makes it difficult when half your family live in the US.