The higher the vaccination coverage is, the more collective protection the population has against COVID-19 health outcomes.
Nicholas Steyn, Professor Michael Plank, Dr Rachelle Binny, Professor Shaun Hendy, Dr Audrey Lustig, Dr Kannan Ridings


The main purpose of this paper is to develop a model that can be used as the basis for policy advice on border restrictions and control measures in response to outbreaks that may occur during the vaccination roll-out.


We use a mathematical model to estimate the effect of New Zealand’s vaccine rollout on the potential spread and health impacts of COVID-19 and the implications for controlling border-related outbreaks.

We consider a range of scenarios at different stages in the vaccine roll-out, including an unmitigated epidemic and contained local outbreaks. This work is intended to form a foundation for further COVID-19 vaccination modelling in New Zealand that will account for additional demographic variables.


Our results show that, under baseline vaccine effectiveness assumptions and with R0 = 4.5, vaccination of over 80% of the population will likely be necessary to reach the population immunity threshold, defined as a reproduction number that is less than 1 in the absence of other interventions. This would almost certainly require vaccination of at least some under 16 year olds. If R0 = 6 (which could represent a highly transmissible SARS-CoV-2 variant such as Delta), population immunity would require approximately 97% of the population, something which is unlikely to be achievable in practice.


Our results suggest that, until we get close to the population immunity threshold, a major public health response that included significant interventions would still be required to control any resurgent outbreaks and prevent a major epidemic.

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First published: Jun 30, 2021
COVID-19 Modelling Aotearoa
[COVID-19 Modelling Aotearoa](, is a cross-organisation and transdisciplinary group of academic researchers and scientists that were brought together by Te Pūnaha Matatini to help Aotearoa New Zealand face the COVID-19 pandemic. Our work is underpinned by Te Tiriti o Waitangi, fast and committed peer review, and ethics. These parameters ensure that the modelling developed by our broad team is uniquely equipped to provide scientifically robust results which are fit for Aotearoa New Zealand and support our decision-making.