Data illustrates COVID vaccines ‘our strongest tool’ against transmission and death

Jolyon Attwooll

10/11/2021 5:01:38 PM

A new study shows just how effectively vaccines have stopped severe illness and death in NSW. One of its authors tells newsGP what needs to be done to maximise their effect.

NSW on a map
The new data includes eye-catching details of how vaccines have muted the spread and damage done by COVID-19 in NSW.

It is the graphs in a new NSW Health In Focus report that perhaps reveal the most about vaccines’ impact on the Delta outbreak in New South Wales.
A collaboration with the National Centre for Immunisation Research and Surveillance (NCIRS), the NSW Health study contains diagrams with eye-catching details of how vaccines have muted both the spread and damage done by COVID-19 in Australia’s most-populous state.
One graph illustrating the key metric of deaths and ICU cases per 100,000 residents shows unvaccinated people were more than 16 times more likely to die or get severely ill when cases were spreading fastest.
In some categories, the protection offered was higher again, particularly among those aged 50–59 and 60–69. Another graph shows just how far vaccination has stifled the spread of the disease in vaccinated adolescents.
NCIRS Director Professor Kristine Macartney is one of the authors of the report. She said it is the first in a series that will scrutinise the ongoing impact of vaccination – and agrees the graphs tell a significant story.
‘It’s certainly a first and important look at how effective [vaccination] is,’ she told newsGP.
‘We’ve seen the impact in real-time, as we’ve seen hospitalisations and deaths fall in New South Wales while we’re simultaneously able to enjoy more freedoms.
‘They are demonstrating that among our highly vaccinated population, we’re seeing a strong impact.’

Unvaccinated people were more than 16 times more likely to be severely ill or die in the recent NSW COVID-19 outbreak (please note, some data points are approximate).

‘Inevitable’ rise in breakthrough infections
While reassuring for now, the picture is constantly evolving. NSW recorded just 216 new cases on Wednesday, more than seven times lower than when the outbreak peaked in mid-September.
Fewer people are now going to hospital, but the proportion of people with breakthrough infections has risen since the study period, according to the latest COVID-19 Monitor report published the Agency for Clinical Innovation (ACI). In the most recent release, it reports 18.4% of those in hospital as being fully vaccinated.
Professor Macartney describes the shift as ‘inevitable’, with the vast majority of adults in the state now having had the primary vaccine course.
‘Now we have 90% two-dose vaccinated, it is simple mathematics that we will see [more] people infected who are vaccinated.’
‘We’re already seeing people who are either vaccinated or infected in the past … become infected. But the main thing is that they’re not in hospitals on a ventilator or dying from the virus.
‘No matter what the number is, vaccination is clearly highly protective.’
The role of boosters
One of the more sobering graphs in the In Focus report shows that while vaccination offers a large degree of protection, those aged over 80 remain vulnerable.
The difference between the level of vaccinated and unvaccinated infections was the smallest among this eldest age group. The report cites an average of 61 infections per 100,000 in those who had both vaccine doses, compared to 193 per 100,000 in the unvaccinated group.
From 16 June – 7 October, the timespan of the report, there were 47 people who died with COVID-19 despite having two doses of the vaccine. Their average age was 82, with 29 deaths among aged care residents while 18 others had significant comorbidities, the report says.
‘Every decade of life increases your risk of becoming seriously ill or dying from COVID,’ Professor Macartney said.
‘Of course, anyone of any age can die from COVID but the likelihood of that happening increases with age.
‘What we’ve seen from vaccine effectiveness in studies overseas is that there is waning and it does appear to be greater in older people.
‘So having a booster at around six months after completing the first two shots is important, particularly for older people and people with underlying medical conditions.’

The difference in the ICU/death rate was particularly pronounced in people aged 60 and over (please note, some data points are approximate). 

Focus on efficacy
While the report illustrates the impact of the vaccine rollout so far, Professor Macartney has said much more will need to be done to determine the precise efficacy of the vaccines.
With the almost globally unique circumstances of Australia’s low level of COVID-19 in the community, this may not play out exactly as it has elsewhere.
‘The reason we need to do these studies is because we’re different to the UK, US and Canada,’ Professor Macartney said. ‘They’ve had the virus continuously.’
She believes both the lower previous infection rates and different patterns of vaccine use – with the US and Canada relying more heavily on mRNA vaccines, for example – could mean waning and protection is distinct in Australia.
‘We’ll be looking at that very closely, but it must be done very meticulously using the scientific method to calculate vaccine effectiveness.
‘We can’t just take the rate in this report because we haven’t adjusted for things like age, time since vaccination, and underlying conditions.’
Behavioural confounders are also likely to be a factor, highlighting the different ways some people can approach testing.
‘Some people get a lot of tests, even though they are never symptomatic and they might be picked up,’ Professor Macartney said. ‘You’ve got to be able to pick out those people from those who are being tested infrequently.
‘That can influence the way that we calculate vaccine effectiveness.’
GPs and the task ahead
With boosters now underway and most of the population with at least some protection, Professor Macartney indicates the vaccination program is at a transitional phase.
‘For general practice it’s now about starting to deliver those booster doses [and] hopefully also having the difficult conversations with the remaining few who, for unfortunate reasons, have very great concerns about being vaccinated.
‘The most important message is the vaccination program is our strongest tool in the toolbox.’
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