Extract from ABC News
Researchers are trying to keep up with new COVID-19 variants by making new vaccines. (Getty Images: 5/15 WEST)
COVID-19 is evolving and with it the need for new vaccines to protect people against serious illness and death.
Australia has detected its first cases of the highly transmissible XEC "recombinant" variant — a mix of two previous Omicron variants called KS 1.1 and KP 3.3.
Researchers have been working to ensure immunisations that provide an adequate level of protection against new COVID-19 variants are widely available to the community.
So if there are always new variants, how do scientists keep up with mutations and update the vaccines?
How are mRNA COVID-19 vaccines made?
When reports of coronavirus first emerged, researchers quickly obtained a genomic sequence of SARS-CoV-2 — the virus that causes COVID-19.
This helped researchers work out the genetic make-up of the virus and how it causes disease in people, according to the National Human Genome Research Institute (NHGRI).
mRNA COVID-19 vaccines contain a message or code of the spike protein. (Supplied: Doherty Institute)
Once scientists analysed the genetic sequence, they identified the spike protein as the most effective target for the immune system and created a copy or code for it.
Unlike traditional vaccines that contain an inactivated or weakened version of the virus, mRNA COVID-19 vaccines contain a message or code that is delivered to someone's cells.
Doherty Institute professor of virology Damian Purcell said that spike protein code — or RNA message — was "packaged" into lipids to keep it protected for distribution in syringes.
Professor Purcell said once the mRNA vaccine — or message — was injected into a person's muscle, it instructed their cells to reproduce the spike protein.
"These are little bubbles of fat, four different lipids, that together encase the RNA [and] enable it to be protected as it is packaged into syringes and injected into your muscle," Professor Purcell said.
"Those lipids facilitate the uptake and delivery of the essential messenger RNA — the message to be coded within your own cells so your own cells start making the … spike protein."
Damian Purcell says mRNA vaccines are quick and easy to develop. (Supplied)
The process triggers an immune response which creates spike protein antibodies.
The NHGRI said those antibodies remained in the body and recognised the virus if someone became infected, attacking the antigen before it reached healthy cells.
How are vaccines modified to keep up with new strains?
Westmead Institute for Medical Research Centre for Virus Research director Tony Cunningham said new strains emerged when the SARS-CoV-2 spike protein changed, making the virus more transmissible.
Professor Cunningham said the mRNA vaccines allowed scientists to change the spike protein code and update the vaccine with the new message.
The spike protein of an mRNA vaccine is changed to adapt to a new variant. (ABC News: Ongerung Kambes Kesolei)
"If you actually think about RNA like DNA is coloured beads on a string — four coloured beads and they vary along the string — then it's in essence changing that sequence," he said.
"You can just simply change the middle bit of the RNA and that can be done very quickly.
"That spike protein is the one that actually allows the virus to attach to the cell and what we want to do is produce antibodies that stop viruses attaching to the cell."
Professor Purcell agreed, saying one of the advantages of mRNA vaccines was they could be changed and produced usually within a month.
"It's actually one of the really powerful aspects of the mRNA technology, is that many, many steps … can remain the same," he said.
Tony Cunningham says new strains emerge when the SARS-CoV-2 spike protein changes. (Supplied)
Professor Cunningham said the key to responding quickly to new variants was maintaining good surveillance.
He said it was up to the World Health Organization to recommend what strains should be included in updated vaccines.
Professor Cunningham said the vaccines then needed to be approved by the Therapeutic Goods Administration (TGA) in Australia to make sure they were safe and effective, a process which could take about two months.
Why do vaccines need to be updated?
COVID-19 vaccines need to be updated because they cannot protect against newer strains of the virus as effectively, according to Professor Cunningham.
He said that was because the immune system did not have the same antibodies to recognise and fight off the mutated virus.
Damian Purcell says while people still have some immunity from the original vaccine, it is not enough. (AP: Pfizer)
"Variants can change so they're no longer completely protected against the antibodies that are circulating," Professor Cunningham said.
"That's why we need to keep changing our vaccines, and … particularly in aging people, we need to be immunised every six months to keep the antibodies up."
Professor Purcell said the first Omicron strain was an "escape" variant that required an updated vaccine.
"When the first Omicron came, it had many, many, many changes — more than we'd ever seen before and that was a very significant escape variant," he said.
"People vaccinated with the ancestral strain of vaccine were not protected from transmission with that COVID variant."
He said while people still had some immunity from the original vaccine, it was not enough.
"We do have some underpinning immunity that's capable of still preventing severe disease from those infections but it is still relevant enough to develop a new strain of vaccine," he said.
What vaccines have been approved for use in Australia?
Australian Department of Health statistics showed 72.3 million doses of the COVID-19 vaccine had been administered as of October 9.
Pfizer's Omicron XBB. 1.5 and original vaccines were approved for use in children aged five to 11 years old, while Pfizer's original vaccine was also available for children aged six months to four years.
Pfizer's Omicron XBB. 1.5, Original/Omicron BA.4/5 and Moderna's Omicron XBB. 1.5 were available for people aged 12 years and older, according to Healthdirect.
The TGA said it was evaluating Pfizer and Moderna's JN.1 strain vaccine for use in Australia.
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