The new Omicron-targeting COVID-19 vaccine has begun rolling out across Australia.
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So, if you're up-to-date with your boosters, will you need to get this one too?
ACM spoke to the experts to find out everything you need to know right now.
Why is there a new vaccine?
The original vaccines were developed from the original Wuhan strain of COVID-19.
That original vaccine is not as efficient in fighting the virus as it mutates and evolves.
As the virus changes, so must the vaccine.
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"Vaccines based on the original Wuhan variant (i.e. most) 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," said Professor Jeremy Nicholson, Pro Vice Chancellor for the Health Futures Institute at Murdoch University.
"The virus has been evolving in fits and starts for the last three years and continues to do so.
"The more infections there are the more likely the virus is to mutate, it's just about probabilities."
Why target the Omicron strain?
If the virus is going to keep evolving, why create a vaccine that specifically targets the Omicron strain?
Because Omicron is proving to be dominant and is the root of the circulating mutations.
"They [the vaccines] should be even more effective for the latest and most prevalent variants such as Omicron BA.4 and BA.5," Professor Nicholson said.
"These latest sub-variants account for more than 98 per cent of all the world's current SARS CoV-2 infections."
How does this vaccine work?
This vaccine has been developed by Moderna and is a 'bivalent' vaccine.
That means it stimulates an immune response against two different strains of the COVID-19 virus.
"The new bivalent Moderna vaccine contains the BA.1 subvariant of Omicron in addition to an earlier strain of COVID-19," Associate Professor Senjaya Senanayake, a specialist in infectious diseases at the Australian National University said.
So, how effective will this vaccine be against the migrations in the Omicron strain?
Trial data showed that the antibody response was strongest against exposure to the BA.1 Omicron strain.
That antibody response, understandably, weakened against the mutated BA.4 and BA.5 strains.
"UK data examined the risk of hospitalisation with Omicron 15 weeks after a booster with the 'old' mRNA vaccines that don't contain an Omicron subvariant," Professor Senanayake said.
"They found that these 'old' vaccines still provided good protection against severe disease 15 weeks later."
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Professor Senanayake, therefore, advises that if you are eligible for a booster, consider having the new Moderna Omicron vaccine.
But otherwise, you will be protected against the virus all the same if you continue to be boosted with the previous mRNA vaccines.
"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," he said.
"But the current mRNA boosters still do a great job too."
If this vaccine targets the Omicron strain, does that mean previous variants are no longer a concern?
Other variants, including the Delta and Centaurus strains, are still circulating, but each mutation has been superseded by the next.
Eventually, the previous versions die out as the newer versions take greater hold of the population.
"One of the reasons variants emerge is because they outcompete the previous variants, or the previous versions, of the virus," said Associate Professor Hassan Vally, an epidemiologist at Deakin University.
"The new virus is bigger and better and faster and more infectious and more able to evade immunity. So it replaces the previous variant. My understanding is that there's not much of these previous variants circulating."
Do you need this one if you've had all of your previous boosters?
Professor Vally told ACM the time is coming when the COVID-19 vaccine will become part of our usual booster doses.
"We're probably going to be in a situation where we constantly need to top up our immunity," Professor Vally said.
"So regardless of whether you were getting one of these new vaccines or [you're] just getting boosters that were based on the existing formula for the vaccines, I think if you want to have maximum immunity, we're probably going to move to a situation where people will have to regularly update their vaccines."
So, if you're coming up to needing another booster, why should you consider getting this new Moderna Omicron vaccine instead of an earlier mRNA vaccine?
Professor Nicholson said it's all a game of probabilities and hedging your bets against any future outbreaks.
"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," Professor Nicholson 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, i.e. one that creates more severe disease."
It's also more than likely that the next variants of concern will be mutations of the original Omicron strain, just like the Delta, Beta and Omicron grew out of the original Wuhan strain.
"The new Omicron tuned vaccine will probably be more effective against the next versions of the disease, which will be Omicron-derived than previous vaccines, and that is a good enough reason to get boosted again," said Professor Nicholson.
Do you need this one if you've had COVID-19?
As Professor Nicholson describes it, the new Omicron vaccine is "insurance for the future".
If you've had COVID-19, you may have a slight boost to your immunity for a short amount of time, but re-infection is a real concern.
And with re-infection comes increased long-term health risks.
"The people who get the most severe effects of COVID-19 are, unsurprisingly, the unvaccinated or have let their immunity drop, even triple vaccination drops off by about six months," Professor Nicholson said.
"So boosters will always help and may be required for years to come. Age is less of an issue than it used to be, and of course, even young people can get long-COVID.
"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.
"That means regularly boosting protection with the best currently available vaccine. COVID-19 is with us for the foreseeable future and adapting to it requires long-haul vaccine vigilance for all of us."