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Effectiveness of COVID-19 Vaccination Against Covid-19 Specific and All-Cause Mortality in Older Australians

25 Pages Posted: 16 May 2023

See all articles by Bette Liu

Bette Liu

Children’s Hospital at Westmead - The National Centre for Immunisation Research and Surveillance (NCIRS)

Sandrine Stepien

National Centre for Immunisation Research and Surveillance

Timothy Dobbins

University of New South Wales (UNSW) - School of Population Health

Heather Gidding

National Centre for Immunisation Research and Surveillance

David Henry

University of New South Wales (UNSW) - School of Population Health

Rosemary Korda

Australian National University (ANU) - National Centre for Epidemiology and Population Health

Lucas Mills

Department of Health and Aged Care, Commonwealth Government of Australia

Sallie-Anne Pearson

University of New South Wales (UNSW) - School of Population Health

Nicole Pratt

University of South Australia - Quality Use of Medicines and Pharmacy Research Center

Claire Vajdic

University of New South Wales (UNSW) - ARC Centre of Excellence in Population Ageing Research (CEPAR)

Jennifer Welsh

Australian National University (ANU) - National Centre for Epidemiology and Population Health

Kristine Macartney

Children’s Hospital at Westmead - The National Centre for Immunisation Research and Surveillance (NCIRS)

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Abstract

Background: Few studies have examined effectiveness of COVID-19 vaccines against COVID-19 and all-cause mortality across different pandemic periods in 2022.

Methods: We used linked whole-of-population data from the 2021 Australian Census, Australian Immunisation Register, death registrations and other national datasets including migration data. Among 3.8 million adults aged 65+ years and >170,000 aged care residents, we used survival analysis to estimate vaccine effectiveness (VE) against COVID-19 specific mortality and all-cause mortality, by vaccine dose and time since receipt, adjusted for age, sex and other factors. We also estimated absolute COVID-19 mortality rates.

Results: From January-May 2022 (Omicron BA.1/2), 3250 COVID-19 deaths occurred; from June-November (Omicron BA.4/5) 3185 COVID-19 deaths occurred. During January-May, VE of a 3rd COVID-19 vaccine dose within 3 months was 93% (95%CI 93-94%) whilst VE of a 2nd dose >6 months since receipt was 34% (26-42%). During June-November, VE of a 4th COVID-19 vaccine dose within 3 months was 84% (82-86%) whilst VE of a 3rd dose >6 months since receipt was 56% (50-62%). VE estimates for aged care residents were similar, but absolute risk reductions were substantially greater. During June-November 2022, we estimated for every 157 aged care residents boosted with a 4th dose, one COVID-19 death was prevented, this compares to 1458 adults boosted per death prevented in those 65+ years.

Conclusions: COVID-19 vaccination is highly effective against COVID-19 mortality among older adults although effectiveness wanes with time since the last dose. Our findings emphasise the importance of continuing to administer booster doses, particularly to those at highest risk.

Funding: This study was funded by the Australian Commonwealth Government Department of Health and Aged Care.

Declaration of Interest: The study authors have no competing interests to declare.

Keywords: COVID-19, vaccine effectiveness, mortality, waning effectiveness

Suggested Citation

Liu, Bette and Stepien, Sandrine and Dobbins, Timothy and Gidding, Heather and Henry, David and Korda, Rosemary and Mills, Lucas and Pearson, Sallie-Anne and Pratt, Nicole and Vajdic, Claire and Welsh, Jennifer and Macartney, Kristine, Effectiveness of COVID-19 Vaccination Against Covid-19 Specific and All-Cause Mortality in Older Australians. Available at SSRN: https://ssrn.com/abstract=4445191 or http://dx.doi.org/10.2139/ssrn.4445191

Bette Liu (Contact Author)

Children’s Hospital at Westmead - The National Centre for Immunisation Research and Surveillance (NCIRS)

Westmead
Australia

Sandrine Stepien

National Centre for Immunisation Research and Surveillance ( email )

Australia

Timothy Dobbins

University of New South Wales (UNSW) - School of Population Health ( email )

Heather Gidding

National Centre for Immunisation Research and Surveillance ( email )

David Henry

University of New South Wales (UNSW) - School of Population Health ( email )

Rosemary Korda

Australian National University (ANU) - National Centre for Epidemiology and Population Health ( email )

Canberra
Australia

Lucas Mills

Department of Health and Aged Care, Commonwealth Government of Australia ( email )

Canberra
Australia

Sallie-Anne Pearson

University of New South Wales (UNSW) - School of Population Health ( email )

Nicole Pratt

University of South Australia - Quality Use of Medicines and Pharmacy Research Center ( email )

Adelaide, 5001
Australia

Claire Vajdic

University of New South Wales (UNSW) - ARC Centre of Excellence in Population Ageing Research (CEPAR) ( email )

Jennifer Welsh

Australian National University (ANU) - National Centre for Epidemiology and Population Health ( email )

Kristine Macartney

Children’s Hospital at Westmead - The National Centre for Immunisation Research and Surveillance (NCIRS) ( email )

Westmead
Australia

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