(Image: AAP/Dan Himbrechts)

The virus is now among the Australian population in ways we have not experienced before. Once Delta has established undetected community transmission, it is nigh on impossible to stop it if vaccination coverage is low, no matter how early you catch it. 

Australia’s reopening has become contentious. The four-phase pathway out is vague, and debates have ignited on the right time to do it.

Infections and their effect on hospitalisations and mutations need to be a focus as we reopen slowly and steadily, with restrictions eased accordingly. My modelling shows we are on track to live with the virus but control the disease from the first quarter of 2022. 

The vagueness of the reopening pathway is likely to be deliberate: it needs to be adjustable, with restrictions implemented and eased based on forward projecting modelling.  

A delicate balance

COVID-19 vaccines have proved more successful than we had dared hope, reducing the risk of serious illness and death by 95%. US data shows a 10-fold decrease in risk for both hospitalisation and death among the vaccinated.

But vaccination lowers risk in other ways too. The risk of any infection is lowered, not just symptomatic disease. UK data shows the infection rate in vaccinated people to be one-third of that in the unvaccinated and the latest US data shows a 10-fold decrease in infection risk. 

However, high vaccination rates don’t equal zero risks. While transmission is greatest among young adults where the consequences of infection are less, the greatest health impact is felt among those who are less mobile and contribute less to infection rates. 

This doesn’t mean the young and healthy are immune. If too many become ill, hospitals become overwhelmed and everyone’s health is potentially compromised. Mapping the road out then is as much about our healthcare capacity as it is about the deaths we will tolerate.

With lower infection rates, public health responses like test and isolate and other safety measures become more effective, enabling greater infection control without the need to resort to the more extreme measures the Delta variant has necessitated with its greater propensity for spread. 

Mutations must be a focus

The fewer infections there are, the less viral replication there will be, and the slower the mutation clock and emergence of new variants of concern. This will preserve the effectiveness of our current vaccines and provide more lead time for next-generation vaccines should vaccine escape variants still emerge. 

This is classic communicable disease control practice and explicit in Australia’s staged changes in our COVID response. Once we succeed in driving the vaccine wedge between infection and serious disease, and place sufficient downward pressure on the transmission potential to allow us a greater measure of control, we can manage this as we do our other infectious diseases — through surveillance, infection management and outbreak control. 

International borders not so risky

NSW Health data show infection rates among returned overseas travellers are low with offshore screening in place, less than five in a thousand, and only 4% of these in fully vaccinated people. As the risk within matches or exceeds the risk without, safety barriers are less consequential. 

There is no longer a debate to be had about when we open up as a country, much less if. Embedded community transmission makes the international border just one of the many infection controls measures that can be gradually eased as we let vaccination coverage do more of the work.

This is how we will move through the phases of the national plan — not taking daring leaps into the unknown, but measured steps that will seem less controversial as we get closer to the vaccination targets. 

Our progress will be closely monitored using hospitalisations as the barometer of our overall vaccine protection and infection control. If the vaccination targets don’t coincide with the predicted levels of control the modelling suggested, or if current infection levels persist and require a greater level of control, plans can be adjusted, but we will know well in advance if this is likely. 

The one thing really in our control is our state of preparedness.