Authors
Eamon P Raith, Hao Z Wong, Joshua V Ross, Samuel Ziesing, Imogen Asser, Michael Maclean, Krishnaswamy Sundararajan, Lauren Fielke, Shailesh Bihari, Caroline Miller, Nicola Spurrier, Mark Plummer
Published in
Health security. Pages 23265094261480546. Oct 07, 2026. Epub Oct 07, 2026.
Abstract
On November 23, 2021, South Australia lifted border restrictions allowing passive entry of COVID-19 cases into the community. On this date the adult South Australian population was highly vaccinated and COVID-19 naïve (prior infection rate <1:1000). There are no previous outcome data following introduction of SARS-CoV-2 to a susceptible population that was highly vaccinated. The aim of this study was to measure the effect of sole vaccine-derived immunity against SARS-CoV-2, in a virus-naïve population without prior community transmission. This retrospective cohort study of 132,579 adults with COVID-19 was conducted between November 2021 and March 2022. The primary outcome was in-hospital mortality; secondary outcomes were hospital and intensive care unit admission, stratified by vaccination status. Risk-adjusted multivariable logistic regression analysis was performed using a Bayesian framework. Unvaccinated patients had increased odds of death (OR 3.78, 95% credible interval [CrI] 1.20 to 10.58, Bayesian probability of effect [Pr] 0.99), hospital admission (OR 23.9, 95% CrI 19.38 to 29.13, Pr 1.0), and ICU admission (OR 4.68, 95% CrI 1.58 to 12.34, Pr 1.0). Exclusively vaccine-derived immunity against SARS-CoV-2 is unequivocally protective against hospitalization and death. South Australia's pandemic response may be informative in planning for future pandemics, and management of future variants of SARS-CoV-2.
PMID:
42844724
Bibliographic data and abstract were imported from PubMed on 08 Oct 2026.
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