COVID-19 cases and hospitalisations are on the rise across the country and there are calls for further protection to be made available to Australians who want it.
The Australian Technical Advisory Group on Immunisation (ATAGI) currently only advises four doses of a COVID vaccine for Australians over 30 years of age, and three doses for 16 to 29-year-olds, and two doses for those under 15 years of age.
Only adults with a severely compromised immune system are eligible for a fifth dose, while children under 16 can only access a booster dose with severe health conditions or disability.
As new variants emerge and infections climb, some Australians argue they should have the option for an additional booster dose.
How vaccinated are Australians?
While uptake of the first two vaccine doses was incredibly high in Australia — thanks in part to mandates and vaccine economy measures — uptake of third and fourth doses has not been as high.
About 97.3 per cent of Australians over the age of 16 have received one dose of a COVID-19 vaccine and 95.9 per cent have received a second dose.
However, just 69.2 per cent went on to receive their third dose, while only 24.4 per cent of Australians have gotten a fourth dose.
The drop-off in uptake may be accounted for by stricter eligibility conditions.
Fourth doses are only available to Australians over the age of 30 or immunocompromised Australians over 16.
These doses are only recommended at least three months after a third dose or a COVID-19 infection.
ATAGI currently does not support making the second "winter" booster dose available to healthy adults aged less than 30 years "as it is unclear whether the benefits outweigh the risks in this population".
Is there a demand for more boosters?
As shown by vaccination statistics, smaller and smaller cohorts have getting jabbed with the next available booster.
It's a trend that University of Sydney social scientist Julie Leask called "stagnation".
"I think what's happening with the stagnation in boosters is that people have become familiar with COVID," Professor Leask said.
"We tend to be a little bit more relaxed about diseases we're quite familiar with."
While a Herald Sun report said that ATAGI will "almost certainly" advise fifth doses in January 2023, Professor Leask said a major focus should be on administering the eligible Australians with the currently advised vaccinations.
"A quarter of over 65-year-olds haven't had a fourth dose. For Aboriginal people over 30 years of age, only 34 per cent have had a fourth dose," she said.
"Let's focus on getting high coverage in those groups, because that's where we'll see the most benefit from vaccination."
Are boosters effective against new variants?
With the evolution of new variants, questions have been raised as to the efficacy of existing vaccines against new strains.
An October 2022 study published in The Lancet on the effectiveness of the Pfizer-BioNTech vaccine found that "estimates for vaccine effectiveness against BA.4/5 after two doses were 50 per cent or lower … regardless of outcome and time since last dose."
Moderna's combination booster Spikevax Bivalent Original/Omicron was rolled out for use in October for Australians aged 18 and over.
Preliminary results showed what ATAGI called "a small incremental benefit" in an immune response against Omicron subvariants BA.1, BA.4 and BA.5.
However, the speed of viral evolution means the combination Omicron COVID booster may also soon be mismatched to the prevalent strain.
While the BA.5 strain remains dominant in many Australian states, newer BQ.1 and XBB variants are already beginning to supplant it according to wastewater testing.
Is another vaccine dose logistically feasible?
Should ATAGI advise a fifth vaccine dose (or fourth for under-30s), the government has assured it has enough doses to cover everyone.
The Australian government currently has five separate agreements for the supply of COVID-19 vaccines.
These agreements allow for the provision of 250 million doses collectively from Pfizer, AstraZeneca, Novavax, Moderna and the COVAX Facility.
Of that guaranteed supply, 63.9 million doses have been administered in Australia so far.
Supply chain constraints have led some companies such as Moderna to delay delivery of some vaccines until 2023, but the Department of Health and Aged Care said that Australia's vaccine supply had not been affected by Moderna's supply issues.
"The Australian government has adequate supply to ensure all eligible Australians are able to receive their booster dose," a health department spokesperson told the ABC.
With more than enough doses available, the question will be whether Australians will seek out another booster if it becomes available.
How do vulnerable Australians feel about the state of play?
David Christensen lives in the Melbourne suburb of Wantirna South and has spent all his efforts in recent weeks attempting to get another booster dose of the vaccine.
Mr Christensen has Type 2 diabetes — not considered to be immunocompromised — and has been vaccinated with all four available doses.
"I have always been anxious to ensure that I took the earliest opportunity to be vaccinated for COVID-19," he said.
However, Mr Christensen's diligence to obtain boosters immediately when they became available has had the unintended consequence of seeing his protection wane as he waits for a fifth dose to be approved.
"I approached my GP who said that it wasn't possible because the government hadn't approved vaccination, even if the fourth one has started to wane in terms of its effectiveness," he said.
"I didn't feel that hugely impressed with that, because it seems counterintuitive.
"If the vaccination wanes in its effectiveness after six months, surely you can get another one."
Mr Christensen said the irony of the situation was that he was currently in his fourth day of battling a COVID infection, seven months after his last booster dose.
"There's nothing I can do, but just wait to see what ATAGI comes up with," he said.
Are we headed for an annual COVID booster?
Professor Leask said she assumed ATAGI is seriously looking at advising the fifth dose, but expected the process to take time.
"They look at the broad evidence around risk and benefit of introducing another dose in a population," she said.
"We don't want to rush because of pressure from certain quarters."
As for whether demand would follow for sixth, seventh and eighth boosters or whether advice would settle onto a yearly jab, Professor Leask said it was still too early to tell.
"This is a big question mark. When will this stop?" Professor Leask said.
"The decisions about when we will revert to perhaps a yearly COVID booster regime like we have with influenza vaccination won't be able to be made until we see these patterns in COVID waves settle down and we're able better able to assess the risk-benefit profile of having yet another booster."
