People who have had a COVID-19 booster shot are far less likely to die or be hospitalised with the Omicron variant.
An Australian-first study on the effectiveness of coronavirus vaccines has found a third COVID jab provides two thirds more protection from death or hospitalisation from Omicron.
The study also confirmed the schedule of vaccines rolled out in Australia is protecting against hospitalisation and severe disease.
The National Centre for Immunisation Research and Surveillance (NCIRS) led the study that followed two million adults aged 40 and older living in Greater Sydney during the Omicron outbreak in January and February.
It tracked COVID-19 infections, hospitalisations and deaths.
It found having a booster provided 65 per cent better protection against hospitalisation and death from Omicron, compared with someone who had two doses.
People aged over 70 saw significant benefits - the study finding for every 192 people over 70 who was boosted, at least one hospitalisation or death had been prevented.
The study also found reduced hospitalisations and death among boosted people aged 40 to 69.
Senior study author and director of NCIRS Kristine Macartney said the findings built on international evidence on vaccine effectiveness, but were unique as many Australians had not been infected with COVID in late 2021.
"Yet we have shown strong protection against disease from Omicron following an mRNA vaccine as a third dose, irrespective of the vaccine brand given initially," Prof Macartney said.
"Future studies will look at protection gained following a fourth dose of COVID-19 vaccine, which is now recommended for those at highest risk of severe disease."
Lead author of the study Bette Liu said the findings demonstrate the best protection occurs when people follow vaccine recommendations.
In Australia about 70 per cent of the eligible population has received a third COVID-19 vaccine dose.
"I urge those 30 per cent who are yet to receive a third dose to do so as soon as possible," Associate Professor Liu said.
Australian Associated Press
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