Five graphics that explain how Victorias outbreak is tracking

Victoria’s COVID-19 case numbers continue to follow â€" perhaps slightly exceed â€" the Burnet Institute’s projections for reopening, with the growing effect of vaccination counteracted so far by increases in movement among the population.

However, data suggests Victoria is unlikely to have as many hospitalisations and deaths as there were in NSW because the state is further advanced in its vaccine rollout than NSW was when it had similar case numbers.

Modelling commissioned by the Victorian government and released alongside the state’s road map to reopening forecast new cases would reach about 2000 a day on October 10 before plateauing, then jumping again when lockdown lifted at the end of October.

Victoria faces a large number of new hospitalisations in coming days.Credit:Jason South

The end point of the Burnet Institute’s projections are troubling: peak hospital demand of 3150 patients, peak ICU demand of 706, and a better than one-in-two chance of overwhelming the healthcare system.

Although it is early, Victoria is so far tracking on that path â€" or indeed slightly above the predicted daily case numbers.

“Everything seems to be occurring within anticipated ranges so far. But, of course, the further out we go, the more we expect some deviations due to changes in policy or behaviour that were unexpected or unknown a few weeks ago,” said the Burnet’s head of modelling and biostatistics Dr Nick Scott.

As cases rise, so do the number of vaccines in arms; Victoria now has 84 per cent of adults with at least one of their two required doses of vaccine. This successfully helped bend the curve in Sydney, where infections are now tracking down.

Federal government modelling suggests the increase in vaccination is currently responsible for a 25 per cent reduction in virus transmission potential in Victoria â€" versus 35 per cent in NSW.

“The transmission potential has remained fairly steady â€" it just so happens that over the past few weeks the small reduction due to vaccination has balanced out by the small increase due to more mixing,” said University of Melbourne Professor James McCaw, who supplies outbreak modelling to the federal government.

The effect of vaccines is most evident on Victoria’s hospitalisation statistics.

Vaccines from AstraZeneca and Pfizer are about 93 per cent effective at preventing hospitalisation and death. They have also been taken up in greater numbers by people who are more likely to be hospitalised from COVID-19, like the elderly.

In the second wave, a rise in new infections was mirrored closely by a rise in new hospitalisations about two weeks later; it generally takes one to two weeks for an infected person to end up needing to go to hospital.

While hospitalisations are rising in the current outbreak, they are not mirroring new infections as closely.

However, there are substantially more people in the ICU. During the second wave, there was a peak of 45 people needing an ICU bed on August 18. With the current outbreak, there have been more than 45 people in ICU beds each day since September 14. There are currently 114 people in ICU.

This is further illustrated by comparing Victoria’s hospitalisations to NSW’s.

Note how NSW’s hospitalisations rose in lockstep with their cases, yet Victoria’s substantially diverged.

This is likely because Victoria is more advanced on its vaccine rollout than NSW was at a similar point in its outbreak.

When NSW was averaging 1362 cases a day it had 1206 people in hospital, but in Victoria at 1400 cases a day there are 525.

So, there are less than half as many people in hospital in Victoria as there was in NSW at a similar point in its outbreak.

As of Friday, 66 per cent of Victorians in hospital with COVID-19 had not received a vaccine dose. Across the state’s total population [including children], 31.61 per cent have not yet received their first dose.

If the vaccine was not working, you might expect those numbers to be similar. The divergence is evidence people who are not vaccinated are disproportionately at risk of hospitalisation from COVID-19.

Liam Mannix’s Examine newsletter explains and analyses science with a rigorous focus on the evidence. Sign up to get it each week.

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