In the autumn of 2022, Australia found itself confronting a paradox of its own success: a population so thoroughly vaccinated that hospitals appeared, at first glance, to be filled with the protected. The confusion was a lesson in the mathematics of proportion — when nearly everyone belongs to one group, that group will always dominate raw counts, even when its members are far safer individually. Beneath the surface numbers lay a stark and consistent truth: the unvaccinated faced a risk of intensive care fifteen times greater than those who had been vaccinated, a disparity that held across eve
Context matters: Why vaccinated people dominate COVID hospital numbers
Unvaccinated populations face disproportionate hospitalization and death rates; vulnerable populations including elderly and immunocompromised face compounded risk from concurrent flu and COVID.
Unvaccinated people faced a one-in-67 chance of ICU admission
Mark
If 95 percent of people are vaccinated, why should we be surprised to see vaccinated people in hospitals?
Mimi
Exactly. You're seeing the base rate effect. When almost everyone is vaccinated, almost everyone in any group will be vaccinated—including hospital patients. But that doesn't mean vaccination isn't working.
Mark
So the real measure is the risk per person, not the raw count?
Mimi
Right. An unvaccinated person in January had roughly fifteen times the risk of ending up in intensive care compared to a double-vaccinated person. That's the number that matters.
Mark
Why did flu vaccination rates drop so much?
Mimi
Resources and attention went entirely to COVID. People weren't getting their annual flu shots. And because COVID measures were so effective against flu, immunity in the population had declined. Now you have a vulnerable population heading into winter.
Mark
What happens if flu and COVID circulate together?
Mimi
Even modest numbers of flu cases, combined with the COVID wave, could overwhelm hospitals. The system was already under pressure. Two respiratory viruses at once could break it.
Mark
Is BA.2 significantly more dangerous than the original Omicron?
Mimi
Not necessarily more dangerous per infection. But it's 30 to 50 percent more transmissible, so more people get infected. More infections means more hospitalizations, even if the percentage needing care stays the same.
Mark
What's the takeaway for someone deciding whether to get vaccinated?
Mimi
Your individual risk of severe disease depends heavily on vaccination status. The data from January showed that clearly. Vaccination doesn't eliminate risk, but it reduces it dramatically.
The Pulse
- Raw hospital admission numbers were creating a dangerous illusion — vaccinated patients appeared to dominate wards, fuelling doubt about vaccine effectiveness at the very moment protection was most needed.
- The true risk gap was enormous: an unvaccinated Australian faced a one-in-67 chance of ICU admission during the Omicron wave, compared to one-in-1000 for the double-vaccinated — a fifteenfold difference hidden by population mathematics.
- State-by-state data told the same story in different registers, with unvaccinated people comprising half of Northern Territory ICU patients and 35.8 percent of Victorian ICU admissions despite being tiny fractions of their populations.
- A second threat was quietly gathering: flu vaccination rates had fallen during years of COVID focus, leaving population immunity to influenza depleted just as the more infectious BA.2 subvariant began circulating.
- Health authorities were racing to reframe public understanding and drive uptake of both COVID and flu vaccines before winter arrived and two respiratory viruses could simultaneously overwhelm already-strained hospitals.
In the autumn of 2022, Australia found itself confronting a paradox of its own success: a population so thoroughly vaccinated that hospitals appeared, at first glance, to be filled with the protected. The confusion was a lesson in the mathematics of proportion — when nearly everyone belongs to one group, that group will always dominate raw counts, even when its members are far safer individually. Beneath the surface numbers lay a stark and consistent truth: the unvaccinated faced a risk of intensive care fifteen times greater than those who had been vaccinated, a disparity that held across every state and territory. As winter approached, the question was no longer whether vaccines worked, but whether the community would act on that knowledge before a confluence of COVID variants and a neglected flu season tested the health system's limits.
By March 2022, Australia had vaccinated roughly 95 percent of its eligible population — a remarkable achievement that was, paradoxically, generating confusion. Hospital wards filling with COVID-19 patients appeared to contradict official messaging, because the majority of admissions were vaccinated people. The raw numbers seemed damning until you applied the arithmetic most people skip.
Associate Professor Paul Griffin, an infectious diseases physician at the University of Queensland, offered the essential correction: when nearly everyone in a population is vaccinated, you should naturally expect to see mostly vaccinated people in hospital, because vaccinated people vastly outnumber the unvaccinated everywhere. The meaningful question was not who filled the beds in absolute terms, but what each individual's risk actually was.
The per-capita figures told a completely different story. In New South Wales during the Omicron wave, double-vaccinated people accounted for just 0.1 percent of ICU cases, while unvaccinated people — a far smaller share of the population — represented 1.5 percent. Translated into individual odds, a double-vaccinated person faced roughly a one-in-1000 chance of needing intensive care; an unvaccinated person faced one-in-67. The pattern repeated across every state: unvaccinated Australians were dramatically overrepresented in the most severe outcomes, accounting for 30 percent of Queensland's COVID deaths while comprising only 8 percent of its population.
Looking toward winter, Griffin identified a compounding danger. The BA.2 subvariant was circulating at 30 to 50 percent greater infectiousness than original Omicron, while flu vaccination rates had quietly declined during years of COVID-focused public health messaging. Population immunity to influenza had also eroded under pandemic restrictions. The prospect of both viruses surging simultaneously threatened to place unprecedented strain on hospitals already stretched thin. The prescription was straightforward — widespread vaccination against both diseases, administered urgently, before the cold months arrived and the window for preparation closed.
By March 2022, Australia had vaccinated nearly 95 percent of its eligible population. That left roughly four percent unvaccinated or not yet fully protected. Yet when you looked at hospital wards filling with COVID-19 patients, the raw numbers told a story that seemed to contradict everything public health officials had been saying: most of the people admitted were vaccinated.
The confusion was understandable but misleading. To make sense of it, you had to do the math that most people skip. Associate Professor Paul Griffin, an infectious diseases physician and microbiologist at the University of Queensland, explained the arithmetic plainly: when nearly everyone in a population is vaccinated, you should expect to see mostly vaccinated people in the hospital, simply because vaccinated people vastly outnumber unvaccinated people everywhere else too. The real question was not how many vaccinated people were hospitalized, but what your actual risk was depending on your vaccination status.
The numbers, when properly contextualized, painted a starkly different picture. In New South Wales during the Omicron wave between late November and early January, the state health department released detailed breakdowns by vaccination status. Double-vaccinated people made up just one percent of hospital admissions and 0.1 percent of ICU cases. Unvaccinated people, by contrast, represented 8.9 percent of hospitalizations and 1.5 percent of ICU admissions. Translate that into individual risk: a double-vaccinated person faced roughly a one-in-1000 chance of needing intensive care. An unvaccinated person faced a one-in-67 chance. That was a fifteenfold difference.
Other states told the same story through different numbers. In the Northern Territory, unvaccinated people made up half of all ICU patients despite representing a tiny fraction of the population. Queensland recorded unvaccinated people accounting for 30 percent of COVID deaths while comprising only 8 percent of the population. Victoria showed unvaccinated people making up 22.8 percent of hospital patients and 35.8 percent of ICU admissions, despite being just 6 percent of the population. The pattern was consistent: unvaccinated people were dramatically overrepresented in the most severe outcomes.
As Australia headed into winter, Griffin warned of a compounding threat. The BA.2 subvariant of Omicron was circulating and appeared 30 to 50 percent more infectious than the original Omicron strain. Simultaneously, flu vaccination rates had dropped because public health messaging and resources had focused so heavily on COVID. The population's immunity to influenza had also weakened during years of strict pandemic controls. If flu and COVID surged together, the health system could face unprecedented strain. "Prior to COVID, our winter flu surge put a significant demand on the health care systems," Griffin said. The convergence of two respiratory viruses, even at modest levels, threatened to overwhelm hospitals already stretched thin. The solution, he emphasized, was straightforward: vaccination against both viruses, administered widely and quickly, before winter arrived and the variants continued their relentless evolution.
Notable Quotes
The majority of the population is now vaccinated, so it may appear that most people in hospital are fully vaccinated, but the key thing is that the consequences of each infection is still far less because those people are vaccinated.— Associate Professor Paul Griffin, University of Queensland
If we don't get a high rate of protection in the community against flu from vaccination, it could be quite significant. Even modest numbers of flu with the rate of COVID we have now together will put a big demand on our health care system.— Associate Professor Paul Griffin
Want the full story?
Read the original at The Canberra Times ↗
Health & Medicine