If you were hoping for an early Christmas present, you might just be in luck: the federal government has announced updated COVID-19 vaccines will be available from December 11.

That means those who roll up their sleeves could have boosted protection against severe disease and hospitalisation by Christmas Day.

Experts say that's critical given Australia is in the midst of a fresh COVID-19 wave which could see millions infected (or re-infected) in the next few months, according to one of the country's eminent infectious disease experts.

The composition of the two new vaccines, which are already available in the US, is different to those you may have already received.

But that's what makes them more effective at this time.

Let's unpack the details.

What's different about the new vaccines?

The new vaccines are monovalent.

That means they're designed to specifically target one COVID-19 variant.

This differs from the most recent boosters which were bivalent and tailored to protect against both the original strain of COVID-19 and the Omicron variant.

But COVID-19 has mutated several times since Omicron arrived in Australia in 2021, and we no longer see the original strain first detected in Wuhan.

Now, Omicron subvariants EG.5 (nicknamed Eris) and BA.2.86 (dubbed Pirola) are circulating Australia.

The World Health Organization (WHO) says it is "monitoring" Pirola but has classified Eris as a variant of interest given its prevalence.

The new vaccines don't specifically target these strains as they were made for another Omicron subvariant called XBB.1.5 (sometimes known as Kraken).

But that strain is very closely related to Pirola and Eris so the XBB.1.5 vaccines will offer crossover immunity, says Paul Griffin, director of infectious diseases at Mater Health Services.

"It's a much better match for what's going around at the moment."

In addition to the US, these vaccines have already been approved in Canada, Japan, Singapore and Europe.

Why the shift away from previous vaccines?

The WHO has recommended COVID-19 vaccine formulations move away from the original strain.

Infectious disease expert Brendan Crabb told the ABC's News Daily if vaccines keep focusing on the original virus, people will be building immunity to an "irrelevant" strain of COVID-19.

Dr Griffin says there's also a risk that if we continue boosting our immunity to the original strain, we could actually hamper our immune response to new vaccine components targeting subvariants.

That's because "immunological memory" (which protects us from a pathogen long after vaccination) can interfere with the development of updated immune responses.

YOUTUBENew COVID-19 vaccines to be available within weeks.

The Australian Technical Advisory Group on Immunisation (ATAGI) says all currently available COVID-19 vaccines are anticipated to provide benefits, but the new vaccines are "preferred".

"Available data suggests monovalent XBB vaccines provide modestly enhanced protection from severe disease compared to older vaccines," the group said in a statement.

Dr Griffin says people shouldn't take this new advice to mean previous vaccines were ineffective though — they were simply designed to target the virus at a different stage of its evolution.

What will be available?

The two big US pharmaceutical companies Pfizer and Moderna have made the new monovalent vaccines.

Like their previous COVID-19 vaccines, they are both mRNA vaccines. This means they use strands of genetic code to tell the body to construct spike proteins, which then elicit an immune response.

This is what will be on offer as first doses or boosters:

· Low-dose Pfizer XBB.1.5 vaccine for children aged between five and 12

· A higher dose of Pfizer's XBB.1.5 for those over 12

· Moderna's XBB.1.5 vaccine for those 12 and older.

There are no monovalent XBB.1.5 vaccines registered for use in children aged six months to four years old. The original Pfizer vaccine is still the only formulation available for this age group.

The new vaccines were approved by the Therapeutic Goods Administration (TGA) in October but ATAGI also needed to assess them and provide advice to the Minister for Health, Mark Butler about their use.

Monday night Mr Butler accepted ATAGI's advice and announced the December rollout.

"These new vaccines will help protect Australians against current strains of COVID-19 and demonstrate the government's ongoing commitment to provide access to the latest and most effective vaccines," he said in a statement.

But it's worth noting the existing bivalent vaccines will still be available. This contrasts with the US, which took the bivalent Pfizer and Moderna vaccines off the market in September after approving their new XBB.1.5 cousin.

Can I get it?

There is no change to the current vaccine eligibility recommendations by ATAGI, which you can check online.

However ATAGI doesn't recommend getting this updated vaccine if you're up to date with your 2023 boosters (or you had your primary vaccine dose less than six months ago) as you should still be well protected from severe disease.

When will I be able to get the new shot?

The government says doctors and pharmacies can now order the new vaccines which will be delivered from December 11.

Providers who receive their orders earlier don't have to wait until December 11 to start administering them though.

Dr Griffin says he welcomes the long-awaited rollout timeline but wishes it was "a little bit sooner".

He's not sure whether providers will be drip-fed small volumes of the vaccines at first or whether there's a large supply already in Australia.

Why are vaccines still important?

In the next four to five months, Professor Crabb estimates somewhere between 3 and 5 million Australians will get COVID-19 if nothing is done to curb the spread.

He says as a result, tens of thousands of Australians could die early and there could be 50,000 to 100,000 cases of long COVID-19.

While the CEO of the Burnet Institute acknowledges COVID-19 is not an "emergency" anymore, he feels people are being too casual.

"If we don't have a deliberate effort as a world to reduce the amount of transmission, it's hard to see an end to this continual problem.

"It would be fantastic if the [new] vaccine was in people's arms before they encounter the virus."

Dr Griffin says he appreciates there will be a lot of fatigue and anger about the current wave, especially as it coincides with Christmas.

For that reason he says the government needs to create an effective education campaign so people understand how these new vaccines are different and why they're worth getting.

"I think for many people, [boosters] have just become overwhelming … we need to have a really good strategy so we can work on some of those information gaps and get the rate of uptake higher."