Key Points
- Australians can access Moderna's BA.4/5 bivalent vaccine in April
- Bivalent boosters targeting Omicron's original variant and BA.1 variant are available to residents
Victorian Chief Health Officer Professor Brett Sutton urged state residents to get their 2023 booster dose as most had their last COVID vaccine six months ago.
Getting your booster dose is like recharging your phone when the battery is low.Professor Brett Sutton
"Now is a good time to recharge your immunity with the booster dose to prepare for winter," Prof Sutton said.
The 2023 booster dose is available to all Australian adults who haven't had a COVID infection or a booster dose in the past six months.
It is also available to individuals aged 5-17 with medical comorbidities that increase their risk of severe COVID-19.
But how does one decide which of the four bivalent vaccines is best for them?
The right bivalent
The Australian Department of Health and Aged Care said it does not promote one vaccine over another.
Clinical decisions relating to types of vaccines are matters for individuals and their vaccine providersDepartment of Health and Aged Care
However, the eligibility criteria shared by the Department suggest that individuals aged 18 and over can choose either of the four bivalents: Pfizer BA.1, Moderna BA.1, Pfizer BA.4/5, and Moderna BA.4/5.
But those aged 12-18 can only opt for BA.4/5 bivalents.
Associate Professor Stuart Turville from the Kirby Institute at the University of New South Wales said all available vaccines boost protective antibodies against all circulating viruses.
"One thing that is clear in a number of studies is that you need to be beyond two doses of vaccine to provide levels of neutralising antibodies to cover the Omicron lineages presently in circulation," Prof Tuville said.
Data from the Department and the Australian Technical Advisory Group on Immunisation (ATAGI) showed BA.4/5 bivalent vaccines produce higher antibodies.
Antibodies
The Department said Pfizer's BA.4/5 vaccine developed almost 2.9 times higher antibodies against Omicron's BA.4/5 subvariants than those who received Pfizer's original vaccine.
The study was done in adults aged 55 and over.
"Neutralisation of newer BQ.1.1 and XBB.1 subvariants was also higher than with the original vaccine," it said.
The Department said Moderna's clinical trial data showed that BA.4/5 bivalent produced 5.1-6.3 times more antibodies against Omicron's BA.4/5, BQ.1 and XBB subvariants than those who previously received Moderna's original vaccine or the BA.1 bivalent vaccine.
The study was conducted in people aged 18 and over.
Associate Professor Jane Frawley from the University of Technology Sydney said eligible residents may prefer BA.4/5 vaccines over the original boosters.
"New bivalent vaccines are better matched to the current circulating subvariants and are better at protecting us against COVID-19," she said.
Hospitalisation, death and safety risk
The Department, quoting a recent US study, said BA.4/5 vaccine effectiveness against hospitalisation or death was 62 per cent compared with an original booster, which was about 25 per cent.
"The short-term safety data for both the Pfizer and Moderna BA.4/5 bivalent vaccines was similar to the original vaccines when used as a booster," it said.
"No new or unexpected safety signals have been reported," it said.
The Australian Technical Advisory Group on Immunisation said there had been no association between Moderna's bivalent BA.4/5 vaccine and thrombotic stroke (caused by blood clots in arteries supplying blood to the brain).
"The very small risk of myocarditis (inflammation of the heart) or pericarditis (inflammation of the membrane around the heart) following Moderna bivalent BA.4/5 vaccine does not appear to be greater than the risk after a first booster dose of Moderna original vaccine or a booster dose of Pfizer bivalent BA.4/5 vaccine in individuals aged 12 years," the ATAGI said in a statement.
In a separate statement on 8 February, Australia's top vaccine advisory committee noted that the risk of Pfizer's BA.4/5 vaccine was similar to its BA.1 and original vaccine when used as a booster.
Adverse reactions following Pfizer bivalent BA.4/5 as a second booster dose included pain at the injection site (68.5%), fatigue (56.4%), headache (41.4%), muscle pain (25.8%), chills (16.9%), joint pain (13.4%), fever (7.3%), injection site swelling (5.4%), injection site redness (4.8%), and lymphadenopathy (0.3%)ATAGI
Availability
The Australian government has secured the supply of 10 million doses of Pfizer's BA.4/5 bivalent vaccine. It is available to eligible Australians through primary care channels from 6 March.
Three million doses of Moderna's BA.4/5 vaccine are expected to be available from April.
The Moderna and Pfizer Bivalent Original/Omicron BA.1 vaccines are available for those eligible and who want to receive their booster nowDepartment of Health and Aged Care
BA.4/5 as primary doses
Some countries, including the US, are considering BA.4/5 vaccines as primary doses.
The Department said not all countries have the same recommendations about COVID-19 vaccines, and everyone makes their determinations based on various factors.
"The provisional registration for the bivalent vaccines only supports their use as a booster dose at this time," it said.
Prof Tuville said it is difficult to predict the next variant and how it would differ from the current ones.
"However, it has been a long time since the original ancestral variant has been in circulation and moving towards the bivalent doses does make sense," he said.
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