Melbourne got a protective umbrella of vaccine induced immunity right through the epidemic, rather than Sydney's one-month lag in effective coverage.

(Data updated 9 November)

Millions of Australians have been intently watching a titanic struggle between much loved cities and a terrible common enemy.

The fabled Emerald city to the north, and the ageing Victorian financial matron to the south.

Sydney and Melbourne.

It’s been about resting control of the coronavirus epidemic that has raged over many months in both capitals.

Some have mainly seen the management failures and not paid close attention to the marvellous successes. 

And to Melbourne's hard-earned one-month head-start in implementing high quality damage control.

Much of the focus has been on how many cases have been diagnosed every day-- the daily case count.

This post was created on a Cup day that had a further dramatic fall in Melbourne daily cases, with people starting to notice the fruits of long intense mitigation efforts.

But first a graph that shows just how well vaccination worked.

Graph via COVID live Au on Twitter

This shows that (on 11 November 2021) every available indicator of severe COVID-19 disease impact in Victoria has been trending down for weeks.

Hospital occupation.

ICU COVID active cases.

People with COVID on ventilators

Even daily deaths.

That's all thanks to vaccination.

So it's well worth dissecting what's leading to this success.

The tale of Two Cities retold again.

The graphic below compares daily diagnosed cases in the two Australian states being highlighted here, including cases for both cities which make up the great majority of cases in these states.

The outbreak started in Sydney in mid-June and peaked early September in that city.

Melbourne’s outbreak started later and peaked mid-October, and it’s obvious that the Melbourne outbreak in Victoria was larger as measured by peak daily counts of diagnosed cases.

But what’s not always mentioned is a remarkable fact that in terms of serious disease the health impact in Melbourne is only about 50% of the Sydney outbreak. This is shown in a graph the compares hospitalisation occupancy in the two regions during this late winter spring season in the southern hemisphere:

The area of curve for Victoria is about 52 percent of the NSW peak using the left side of both curves. Peak height is about 75 percent. This severe health damage in Victoria was 25-50 percent lower despite higher case numbers.

The low relative hospitalisation in Victoria has been noticed quite widely and was the major reason for early emergence from lockdown emergency containment arrangements in that state.

There has been some discussion of this by social media. A good example is data journalist Juliette O’Brien and there several active Twitter data analysts. There relatively little satisfying discussion about this remarkable health achievement in conventional media outlets.

The difference between the two Australian states in hospitalisation rates is most likely a combination of different aspects improvements in disease recovery-- somewhat lower chances of going to hospital in Victoria coupled with shorter hospital stays. The details of these changes have not yet been transparently discussed but have been reported briefly in mainstream media.

Epidemic health statistics for Victoria are not as complete as those published by the New South Wales government agencies, but for New South Wales we can see some reduction in rates of hospitalisation per infection based on published statistics (and discussed in previous GMO Pundit posts). Hospital ward occupancy numbers are widely reported and also seem to be the most sensitive way to detect this improved health outcome in Victoria.

Intensive care unit occupancy by Covid-19 patients follows a similar pattern to general hospital occupancy, as shown here (but note that Victoria uses different criteria for arriving at the ICU numbers that NSW do):

Again we see approximately 75% of the severe health damage (as measured by peak ICU occupancy values) in Victoria as compared to New South Wales.

It’s possible to go further and compare the two regions as far as the detailed timing of this improvement in protection against severe disease.

The following chart compares the timing of the hospital occupancy curve in New South Wales with the daily case count:

Note that both curves are superimposed until late August but the hospitalisation curve departs from coincidence with the case curve thereafter (near red arrow) but the case curve turns downwards before the hospitalisation occupation numbers start declining. This is expected, because there is a delay after the onset of illness of about 5 days before disease become so severe people need to be taken to hospital.

Mind the Gap.

A similar graph for Victoria is distinctly different in timings of events, but is even better in terms of disease improvement features:

Initially the two curves -- daily cases and hospital occupancy -- may have coincided but they depart from one another about the same calendar time which is a very early stage in the epidemic compared to the New South Wales epidemic. This has resulted in a much stronger departure between the two curves that occurred with the Sydney epidemic meaning much less health damage , and both curves  peak (pink arrow) at about the same time.

If we remember there is a lag between onset of illness and onset of hospitalisation of about 5 days, this strongly suggests that the suppression of hospital occupancy in Victoria by vaccine induced immunity is progressing further than in Sydney and is additional to case numbers drops.

How can we explain this?

From the Pundit's point of view it seems sensible to conclude we are seeing progressively more effective protection from severe health damage from the still ongoing rapid rollout of higher vaccine coverage in both states. Both cities will get to about 90 percent or more immunity in the adult population.

Because the Melbourne outbreak occurred later than the New South Wales outbreak, Melbourne got the protective the umbrella of vaccine induced immunity right through the epidemic, rather than one-month in, as seen in Sydney. Severe health damage was thus about 25 percent less in Melbourne.

This timing of good vaccination coverage can be verified by comparing vaccine uptake curves for the two states (using graphs proved by Mike Honey on Twitter):

The red arrow show the point at which vaccination reached 50 percent coverage, which was midway to the peak daily cases.

In Victoria we have:

Here the red arrow indicating 50 percent vaccine coverage  occurs at a very early stage in the outbreak. This is about 4 weeks earlier than the mid-point stage of rise to the peak case numbers where a red arrow is placed in the corresponding NSW epidemic curve.

Sydney may have turned the case number epidemic earlier, but Melbourne turned around severe health damage though the entire outbreak, and is achieving better overall health protection outcomes.

Let’s hope this message gets wide attention.

Continued as

Timings for saved lives and protection to health from the rapid COVID vaccine rollout in Sydney