Eligible Australians can now access bivalent COVID-19 vaccines.
Moderna’s new booster received approval from the Australian Technical Advisory Group on Immunisation (ATAGI) in September and doses are now being distributed to health providers.
It marks the start of bivalent ‘next generation vaccines’. These contain messenger RNA samples of the original COVID-19 strain and the Omicron BA.1 subvariant that was circulating globally at the beginning of 2022.
These strands of nucleic acid allow the human body to ‘code’ antibodies to attack the SARS-CoV-2 virus when it infects the body.
And although the vaccine is built on a superseded strain of the Omicron variant (BA.1 has widely been replaced by descendent strains like BA.4 and BA.5), clinical trial data has shown it produces a “broad immune response” to these other variants.
Who can get a bivalent vaccine?
Over 95% of Australians are currently vaccinated, 70% are ‘boosted’ and more than 2 in 5 eligible people have received a ‘winter’ booster.
Moderna’s bivalent vaccine is approved for use among people 18 years and over, three months after the more recent of a prior COVID-19 infection, or a previous vaccine dose.
The Moderna bivalent vaccine is the only two-type COVID-19 dose authorised in Australia. Pfizer’s version is still being assessed, although it has been approved in the US, Canada and UK.
How effective is it?
Reported trials found Moderna’s bivalent vaccine produced 1.7 times more neutralising antibodies titres against Omicron BA.1 than the original vaccine. People who had a previous SARS-CoV-2 infection were found to have nearly double the titres against BA.1, and the dose was found to produce 1.2-1.3 times more antibodies relative to the Moderna booster.
ATAGI says it will monitor how this translates to the vaccine’s benefit and duration of effectiveness in the population.
Are any risks involved?
When ATAGI issued its recommendation that Moderna’s bivalent vaccine be used as booster alternative for people aged 18 or over, it also highlighted several considerations.
Importantly, it found the bivalent vaccine has a similar safety profile to Moderna’s original vaccine doses, which has been rolled out to almost every Australian.
The data that emerged from Moderna’s clinical trials for the vaccine showed pain at the injection site was the most commonly reported adverse event (in 77% of participants). 55% of participants experienced fatigue, while around 4 in 10 reported headaches and myalgia (muscle aches).
Although the numbers of clinical trial participants are insufficient to provide indications of the very rare risk of myocarditis or pericarditis, ATAGI emphasised there was “no reason” to anticipate a different level of risk for these symptoms compared to previous Moderna doses.
It’s important to note that the Moderna bivalent can be used as the third or fourth dose of the vaccine recommended by the Australian government.
The government has not recommended individuals receive further vaccination beyond the initial two-dose course, a third dose (described as the first ‘booster’), and a fourth dose (previously described as the ‘winter booster’).
Matthew Agius is a science writer for Cosmos Magazine.
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