Vaccines save Sydney's bacon, yet again. This time Omicron bacon.

Hints that the Omega wave in Sydney is less severe in disease impact than Delta Further decoupling of hospitalisation numbers from daily cases 

There is much talk about the less severe nature of the Omicron variant COVID wave.

A good lead on this topic is this tweet (linked pdf here):

The Australian Omicron wave is attracting it’s fair share of attention, with much valuable chatter on Twitter.

Several previous posts at GMO Pundit have mentioned changes in disease severity during the rollout of vaccination in Australia.

Twitter discussions reveal that a good way to display these changes is by plotting the logarithm of disease metrics against time.

The graph displayed above does this for New South Wales epidemic numbers for the last half of 2021.

To allow for delays before cases turn into disease, average daily cases over a centred 7 day calculation window for reported new cases was used, with a window lag of 11 days prior to day of hospital number plotted.

The graph plots log (average daily cases) and log (reported hospitalisation numbers) against time.

It can be seen that the orange curve representing cases progressively gets lower and lower than blue curves as the weeks of the epidemic rage. This indicates that out of every 100 infections there is less and less time spent in hospital. The trend is either fewer people in hospitals, or shorter stays in the wards, or both. 

Watch the gap.

The gap between the two curves is also plotted in grey . This gap number log (cases)-log(hospital numbers). This dramatically displays the overall time trend from July to December of  decreased epidemic severity .

Most interestingly, the grey curve indicates that acceleration of gap widening is occurring in the latest weeks of the epidemic.

Is this further widening of the gap caused by a shift from mainly Delta variant (severe disease) to mainly Omicron (with less severe disease)? This will get much attention over the next two weeks.

Whatever the answer to this question, the grey graph curve powerfully emphasises the effective progressive mitigation of epidemic severity achieved from strong vaccine rollout.

Vaccines saved Sydney’s bacon yet again.