D.1 Purpose

In Lesson 2 of Chapter 10, we included a ‘spotlight’ on responding to changes in risk and vaccine-related protection, drawing on examples from the Australian states of New South Wales and Victoria.

This PHMS appendix is intended to support that lesson: if vaccine effectiveness wanes, population immunity is perhaps more important than vaccine coverage when it comes to making decisions about when to ease restrictions. This appendix is also intended to demonstrate how – in the next pandemic – the monitoring and forecasting of population immunity from vaccines could be undertaken.

It is not the purpose of this appendix to focus on what happened during COVID-19 in Aotearoa New Zealand and the decisions taken at that time. Rather, we seek to pull out what we think is an important lesson. We use the population of South Auckland in mid- to late 2021 to illustrate what the likely population immunity probably was week by week. Taking the Auckland lockdown during 2021 as our example, we consider how this sort of analysis might be included (alongside other factors) in decision-making on when to ease public health and social measures (PHSMs) in a future pandemic.

To put this in context, decisions about when to ease PHSMs such as lockdowns are based on multiple criteria and can be very challenging to make. There are social considerations (such as the general population’s loss of liberty, and the educational and social impacts for children and young people of not being able to attend school in person), economic considerations (including the impacts on small businesses in the locked down area, and spillover effects for the wider economy), and health impacts (both direct effects of getting infected, and indirect mental health and other effects of long lockdowns). In the case of the Auckland lockdown in 2021, a key focus was the extent of protection for Māori and Pacific populations, who had lower levels of vaccine coverage and higher risk of overall negative health outcomes.

This appendix is designed to help future officials and decision-makers think about one criterion (protection against infection, symptomatic illness and hospitalisation or death) in one domain (health) as an important input into the range of factors involved in deciding when to ease PHSMs.