We present two implementations of an age-structured model for Covid-19 spread in Aotearoa New Zealand with a partially vaccinated population. The first is a deterministic SEIR model, useful for considering population-level dynamics and questions about population immunity. The second is a stochastic branching process, useful for considering smaller community outbreaks seeded by individual border arrivals. This builds on an earlier model used to inform the response to outbreaks of Covid-19 in New Zealand.
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 rollout. We consider a range of scenarios at different stages in the vaccine rollout, including an unmitigated epidemic and contained local outbreaks.
This work is intended to form a foundation for further Covid-19 vaccination modelling in Aotearoa New Zealand that will account for additional demographic variables.