Australian-first study reveals boosters’ efficacy against Omicron

An Australian-first COVID-19 vaccine effectiveness study has confirmed COVID-19 booster vaccines provide effective protection against hospitalisation and death from the Omicron variant of concern.
 
The pre-print study, led by the National Centre for Immunisation Research and Surveillance (NCIRS), tracked more than two million adults aged 40 years and over living in Greater Sydney during the peak of the Omicron wave at the beginning of 2022.
 
It found that the receipt of a booster dose provided 65% greater protection against hospitalisation and death compared to only two doses, with the results especially significant for people aged 70 years and older. Unvaccinated people were excluded from the results.
 
Lead author Associate Professor Bette Liu from the NCIRS and UNSW said the study shows that optimal protection occurs when vaccine recommendations are followed.
 
‘In Australia about 70% of the eligible population has received a third COVID-19 vaccine dose … I urge those 30% who are yet to receive a third dose to do so as soon as possible,’ she said. 
 
‘COVID-19 vaccination and vaccination for other respiratory viruses such as flu are particularly important to reduce health system burden as we see a surge in these respiratory viral infections over winter.’
 
The new research has been released in the wake of a new Federal Government campaign designed to encourage greater uptake of COVID boosters, with the 70.4% nationwide rate of eligible people who have had three or more doses markedly lower than the 95%+ who have had two.
 
Among Aboriginal and Torres Strait Islanders, the booster rate is even lower at 53.8%, while in Queensland only 63.4% of eligible people have been boosted.
 
According to the research, while there was evidence of waning protection against infection after two doses, receipt of a third dose resulted in much higher protection, particularly against severe disease.
 
Vaccination also resulted in enhanced protection in the small number of people who had previously been infected with the Delta variant.
 
The University of Sydney’s Professor Kristine Macartney, who is also Director of NCIRS and senior author of the study, said the research is an important contribution to the international evidence base on COVID-19 vaccine effectiveness and SARS-CoV-2 infection.
 
‘It is unique because much of the Australian population had not previously been infected with SARS-CoV-2 by the end of 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,’ she 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.’  
 
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