COVID-19 cases and vaccination rates: Turning the corners in NSW and VIC
Increased vaccination rates have likely assisted NSW to turn the corner on new COVID-19 cases. Peak daily cases for NSW occurred at 75%-80% first-dose coverage and 45% fully-vaccinated rates. VIC has already surpassed these thresholds however daily cases are still rising. The latest responses from VIC authorities may suggest an expectation of lower healthcare burden due to peak cases occurring amongst a relatively more highly-vaccinated population.
The data for this article is sourced from covidlive.com.au. Analysis notebook available on GitHub.
The states of New South Wales and Victoria in Australia have experienced outbreaks of the Delta strain of COVID-19 in the second half of 2021. Both jurisdictions initially attempted goals of eliminating the virus and achieving zero community transmission. However despite the implementation of lockdown conditions cases of COVID-19 continued to rise, leading to a shift in strategy to one of suppressing runaway growth in case numbers until community vaccination rates increased.
The New South Wales outbreak began in late June 2021 and accelerated during August to a 7-day average peak of 1,432 new cases per day. The Victoria outbreak has shown growth in case numbers during September, with an acceleration in leading into early October, as shown in Figure 1:
The COVID-19 vaccination rollout in New South Wales was accelerated as a result of the 2021 Delta-strain outbreak and subsequent public health measures. Thus the level of vaccinated in the community is ahead of VIC by approximately two weeks as shown in Figure 2:
New South Wales case number have stabilised during September 2021 and began to fall later in the month as shown in Figure 1. However, VIC case numbers continue to climb. Both states have implemented similar lockdown strategies, so it may be feasible to expect that case numbers in VIC will similarly decline when community vaccination rates increase.
Figure 3 presents the case numbers for NSW and VIC against level of first-dose community vaccination for those eligible 16+ years of age. Figure 4 similarly presents new COVID-19 cases against proportion of the community ages 16+ that are fully vaccinated.
Figures 3 and 4 show that the peak of NSW case numbers occurred at 70%-80% first-dose vaccination and 35%-45% fully vaccinated adults. The VIC case numbers are yet to peak, however the state has already passes 80% first-dose vaccination and 50% fully vaccinated thresholds. Thus, the high case numbers of over 1,500 cases/day in VIC are occurring in a more highly vaccinated population.
The daily case numbers for VIC are within the 10%-90% confidence bounds presented in the Burnett modelling and thus not unexpected. Despite increased daily case numbers authorities in Victoria have not implemented any major further public health restrictions. Furthermore the high level of cases in VIC are occurring in a period of high community vaccination rates, thus potentially authorities believe this may lead to fewer hospital admissions and burden on the healthcare system.
NSW COVID-19 cases have turned a corner and declined, together with quicker vaccination uptake then other states in Australia. Peak daily cases for NSW occurred at 75%-80% first-dose coverage and 45% fully-vaccinated rates. VIC has already surpassed these thresholds however daily cases are still rising. However this may be associated with relatively lower healthcare burden due to peak cases for the current outbreak in VIC occurring in conjunction with higher rates of COVID-19 vaccination amongst the population.
The full analysis notebook can be found on GitHub.
