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Modelling herd immunity requirements in Queensland: impact of vaccination effectiveness, hesitancy and variants of SARS-CoV-2.

Authors :
Sanz-Leon P
Hamilton LHW
Raison SJ
Pan AJX
Stevenson NJ
Stuart RM
Abeysuriya RG
Kerr CC
Lambert SB
Roberts JA
Source :
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences [Philos Trans A Math Phys Eng Sci] 2022 Oct 03; Vol. 380 (2233), pp. 20210311. Date of Electronic Publication: 2022 Aug 15.
Publication Year :
2022

Abstract

Long-term control of SARS-CoV-2 outbreaks depends on the widespread coverage of effective vaccines. In Australia, two-dose vaccination coverage of above 90% of the adult population was achieved. However, between August 2020 and August 2021, hesitancy fluctuated dramatically. This raised the question of whether settings with low naturally derived immunity, such as Queensland where less than [Formula: see text] of the population is known to have been infected in 2020, could have achieved herd immunity against 2021's variants of concern. To address this question, we used the agent-based model Covasim. We simulated outbreak scenarios (with the Alpha, Delta and Omicron variants) and assumed ongoing interventions (testing, tracing, isolation and quarantine). We modelled vaccination using two approaches with different levels of realism. Hesitancy was modelled using Australian survey data. We found that with a vaccine effectiveness against infection of 80%, it was possible to control outbreaks of Alpha, but not Delta or Omicron. With 90% effectiveness, Delta outbreaks may have been preventable, but not Omicron outbreaks. We also estimated that a decrease in hesitancy from 20% to 14% reduced the number of infections, hospitalizations and deaths by over 30%. Overall, we demonstrate that while herd immunity may not be attainable, modest reductions in hesitancy and increases in vaccine uptake may greatly improve health outcomes. This article is part of the theme issue 'Technical challenges of modelling real-life epidemics and examples of overcoming these'.

Details

Language :
English
ISSN :
1471-2962
Volume :
380
Issue :
2233
Database :
MEDLINE
Journal :
Philosophical transactions. Series A, Mathematical, physical, and engineering sciences
Publication Type :
Academic Journal
Accession number :
35965469
Full Text :
https://doi.org/10.1098/rsta.2021.0311