What do bivalent vaccines mean for Australia’s rollout?

Matt Woodley

13/10/2022 4:52:08 PM

The first doses of Moderna’s variant-specific COVID vaccine became available this week, offering a slight advantage over previous versions.

Vial of Moderna bivalent vaccine
The bivalent vaccine is not recommended for the primary course of vaccination as each dose only contains 50 micrograms of vaccine. (Image: AAP)

While there may be a lack of clarity regarding the number of doses Australia is set to receive before the end of the year, the rollout of Moderna’s bivalent vaccine has begun, with more than 1000 vaccine providers having already signed up to take part.
Development of the new vaccine (mRNA-1273.214) began shortly after Omicron emerged, with half of each 50 microgram dose aimed at BA.1, while the other half targets the original strain.
Even though other variants have since emerged – in particular BA.4 and BA.5 – the bivalent doses are still expected to provide some additional protection when compared to the first-generation vaccines.
Professor Jeremy Nicholson, Pro Vice Chancellor for the Health Futures Institute at Murdoch University, has welcomed the new vaccine’s availability in Australia.
‘Vaccines based on the original Wuhan variant have not been particularly effective at stopping Omicron, hence the surges seen earlier in the year. They do, however, reduce the severity of the disease,’ he said.
‘The new Omicron-specific vaccines … have been specially tuned to the molecular signatures of the current variants of the SARS CoV-2 virus.
‘They should be even more effective for the latest and most prevalent variants such as Omicron BA.4 and BA.5 … [which] account for more than 98% of all the world’s current SARS CoV-2 infections.’
Professor Nicholson also warned that more variants are likely to emerge and predicted that the bivalent vaccine will ‘probably’ be more effective against the next versions of the disease.
‘The real reason for being vaccinated yet again with the Omicron-tuned vaccine is that we don’t know if there is going to be another virulent variant in the near future,’ he said.
‘I doubt if we will see more infectious variants – because the current Omicron is one of the most infectious disease agents known – but there is nothing to stop a more virulent form from being produced.
‘The latest data shows that repeated infections also increase the chances of getting long COVID, which in turn increases the likelihood of diabetes and heart disease, so avoiding further infections is still important in the long-term.’
However, while the vaccine has been welcomed by many, infectious diseases specialist Associate Professor Sanjaya Senanayake has warned against overstating its utility.
‘Mathematical modelling from Australia has shown that when around 50% of the population is immune to COVID-19 – akin to the situation here – an Omicron-specific vaccine doesn’t add too much of a benefit over the mRNA vaccines that we have been using thus far,’ he said.
‘The take-home message would be that it is good to have the new BA.1 bivalent vaccine if you are eligible for a booster, as it is likely to give a slight benefit for severe disease over the current boosters in the current Australian COVID-19 climate.
‘But the current mRNA boosters still do a great job too.’
This message matches advice issued by the Australian Technical Advisory Group on Immunisation (ATAGI) last month. The guidance indicates that all approved boosters still provide strong protection and that receiving a third (or any other subsequent dose) is preferential to waiting until bivalent access becomes more widespread.
‘Both bivalent and original vaccines result in an improvement in the immune response against BA.1 and BA.4/BA.5 Omicron subvariants, with the Moderna bivalent vaccine showing a small incremental benefit over the original vaccine,’ ATAGI states.
‘The Moderna bivalent vaccine generates a modestly higher level of antibody response against multiple SARS-CoV-2 Omicron subvariants [approximately 1.6–1.9 times] … compared with the Moderna original booster vaccine.’
ATAGI also said while the bivalent vaccine can be used as an alternative for any booster dose in people aged 18 years or older, it is not recommended for the primary course of vaccination.
‘The Moderna primary course requires 100 microgram doses and therefore the Moderna bivalent vaccine is not considered suitable for primary vaccination,’ the advice states.
‘There are no data as yet on the immunogenicity of this bivalent vaccine in a primary series.’
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Dr Irandani Anandi Ranasinghe-Markus   14/10/2022 7:56:08 AM

Is there any advantage to giving the Bivalent Moderna as a third booster dose (i.e 5th vaccine I total), to those who have already had the Moderna spikevax more than 3 months ago?