Aotearoa New Zealand’s 2017 influenza pandemic plan

The most recent version of the pandemic plan was released in August 2017. In the Foreword, the Director-General of Health at the time noted that the plan had been modified to take into account lessons learned during the 2009 influenza A (H1N1) pandemic response, and stated that the plan could be ‘adapted and applied to any pandemic, irrespective of the nature of the virus and its severity’ (Ministry of Health 2017).

The plan proposed that the response should be organised into six phases, with identified trigger points for transitioning between phases ().

Why the plan did not match the pandemic

The 2017 pandemic plan was explicitly designed to be flexible (p57) but this flexibility was framed as allowing for varying levels of severity of a future influenza pandemic. The plan did not adequately consider the possibility of a non-influenza pandemic.

As a result, a key assumption of this plan was that pandemic spread would inevitably exceed the capacity of the response to contain and extinguish clusters. At this point, the plan anticipated pivoting to a mitigation approach, aiming to reduce the impact of the pandemic on the population rather than stopping the pandemic. Thus, the plan implied that as the pandemic progressed, some control measures might be stepped down from the maximum possible; for example reducing the intensity of contact tracing efforts to direct staffing and resources needed to manage large patient numbers.

This approach derived from an assumption that the pandemic being planned for was caused by influenza, and previous experience of influenza pandemics suggested that elimination was not feasible. Influenza is highly transmissible by droplet spread (particularly in children) and the short incubation period (estimated 1·4 days [95% CI 1·3–1·5] for influenza A and 0·6 days [95% CI 0·5–0·6] for influenza B (Lessler et al. 2009)) allows very little time to trace and quarantine contacts before onward transmission has occurred.

The 2017 plan also assumed that a vaccine would be developed quite rapidly after emergence of the pandemic, as would be expected with influenza where there is established global production capability that regularly needs to reformulate the vaccine in response to changes in circulating virus. It did not anticipate the current situation of a coronavirus pandemic requiring prolonged implementation of non-pharmaceutical (i.e. public health) interventions (NPIs) due to lack of effective antiviral treatments and vaccines.

In the Introduction, the authors noted that ‘the approach in the plan could reasonably apply to other respiratory-type pandemics (such as severe acute respiratory syndrome – SARS)’, but this aspect is not further explored in the plan; in particular, there is no discussion about how different transmission characteristics might shape a different type of response. This omission may be an instance of a more general tendency among Western countries that did not experience widespread SARS-CoV or MERS-CoV outbreaks to underestimate the need to prepare for a coronavirus pandemic (Summers et al. 2020). Accordingly, the three key factors identified in the 2017 plan that would inform the pandemic response were:

1. Ease of transmission and severity

2. Vaccine availability

3. Efficacy of treatment on morbidity and mortality.

The implications of these factors for the pandemic response are further described in the plan, noting that in the event of higher rates of transmission and severity, agencies should be prepared for a swift transition to the ‘Manage It’ (mitigation) phase. The trigger for entering the Post-Peak phase was a decreasing number of cases, at which point there would be a move to lift restrictions and restore normal services.

As will be seen, the triggers for action are completely different when an elimination strategy is in place. The 2017 plan, therefore, ruled out adoption of an elimination strategy without explicitly saying so, and without building in a decision step to consider elimination as a possible approach.

Elimination is, however, a well-described control strategy for other infectious diseases (De Serres et al. 2000; WHO 2007; Kelly et al. 2009) and this strategy has proven effective for Covid-19. In the next section, we describe the evolution of Aotearoa NZ’s elimination strategy.

Aotearoa New Zealand’s pivot to elimination

A key turning-point in Aotearoa NZ’s Covid-19 strategy was evidence from China that transmission of SARS-CoV-2 could be contained. In particular, the report of the WHO-China Joint Mission (World Health Organization 2020) provided valuable insights that changed epidemiologists’ thinking about what could be achieved.

The Joint Mission consisted of a team of national and international experts led by Dr Bruce Aylward of WHO and Dr Wannian Liang of the People’s Republic of China. The aim of the Mission was to gather evidence about the outbreak and response to inform action in China and elsewhere.

In their report (dated 16–24 February 2020) the team noted that ‘In the face of a previously unknown virus, China has rolled out perhaps the most ambitious, agile and aggressive disease containment effort in history’ (p16). Given the absence of a vaccine or effective antimicrobial treatment, the public health response in China was based on NPIs, implemented with high stringency. These measures included stay-at-home orders, prohibition of travel, active case and contact management, promotion of hand hygiene, restriction of mass gatherings, and mask wearing. The Joint Mission reported that community transmission was rapidly decreasing in response to these measures.

The insight from China that ‘It is not SARS and it is not influenza’ (p18) was transformative in shaping the subsequent Covid-19 response in Aotearoa NZ.

Achieving and regaining elimination

Because it was recognised that Aotearoa NZ lacked capacity for the extensive testing and contact tracing programme used by China to contain the rapidly-expanding Covid-19 pandemic, and amid rising concern about Aotearoa NZ’s relatively low per capita allocation of emergency ICU beds (Wilson, Telfar Barnard, et al. 2020), epidemiologists argued for a short but intense lockdown or stay-at-home order as a ‘circuit-breaker’ to extinguish all active transmission chains (Baker and Wilson 2020). This order came into effect at midnight on 25 March 2020.

As described elsewhere (Baker, Wilson, and Anglemeyer 2020), the combination of border controls, case and contact management, and intense physical distancing at Alert Levels 3 and 4 were successful in controlling the outbreak, and the country then experienced over 100 days with no new cases in the community. The country subsequently experienced a moderate sized outbreak (the Auckland August Cluster) as well as a series of border failures resulting in small number of infected workers and contacts of returning travellers. All of these cases and outbreaks were controlled, indicating that elimination is a sustainable strategy (Baker, Kvalsvig, Verrall, Telfar-Barnard, et al. 2020; Baker, Wilson, and Blakely 2020).

What types of pathogens need a strategic decision framework?

The experience with Covid-19 has demonstrated the risk of having a pandemic plan that is too pathogen-specific. Assumptions based on management of one pathogen will not necessarily translate to another, and identifying and rejecting unhelpful assumptions may cost valuable time. Aotearoa NZ’s next pandemic plan needs to adapt flexibly to respond to an unfamiliar pathogen, with a consequently broader set of strategies to consider.

A wide variety of pathogens have caused devastating pandemics or epidemics over the last century, including influenza viruses, coronaviruses, Ebola virus, poliovirus, human immunodeficiency virus (HIV), Mycobacterium tuberculosis, and Neisseria meningitidis (meningococcal disease). We now also need to consider deliberate introduction of a known or novel (engineered) pathogen. A recent paper assessed the main pandemic threats that might be sufficiently severe to justify drastic action, notably border closure for island nations. The threats where this action was considered warranted were: Novel non-seasonal influenza (approaching the severity potential of the 1918 influenza pandemic); Smallpox; and two forms of Disease X (an emerging zoonotic disease or a bioweapon) (Boyd et al. 2020b).

These different organisms have caused or could cause very different pandemics. However, not all of these possibilities require a specific pandemic plan, and a plan that attempted to capture all of the different possibilities would be unworkable. It would make sense for the next pandemic plan to focus most strongly on developing an adaptable response framework for pandemics that are:

• At least moderately transmissible: i.e. they have the potential to infect a large proportion of the population;

• At least moderately severe: they impose a high morbidity and/or mortality burden, either generally or in specific populations;

• Require additional controls over and above standard infectious disease control measures that are currently in place;

• Show uncertainty and are not fully characterised: a newly emerging, rapidly evolving pandemic requires application of the precautionary principle until the full extent of the risk is better understood.

Identifying a pandemic as ‘at least moderately’ transmissible or severe will require an integrated assessment of impact. Pandemic impact is a composite outcome of several linked factors, including the effect of patient numbers on health system capacity at different levels of severity, inequities in infection risk or outcome, and multiple measures of disease outcome such as infection fatality risk and occurrence of post-infectious complications in survivors.

The above prioritisation will be particularly applicable to pathogens that are spread by human-to-human transmission during close contact. Such pathogens can readily exploit human travel- and social contact patterns to cause widespread outbreaks in multiple regions (i.e. pandemics).

A pandemic with the above features will require rapid mobilisation of resources and coordination between agencies and community leaders to contain the spread of infection. Hence, there is a need for a framework to guide structured decision-making that can be implemented rapidly when the need arises.

Decision framework for designing a pandemic response

An emerging pandemic requires a thorough and systematic assessment to decide what response is needed.

In the following sections, we describe the key steps in developing a pandemic response, finally assembling the steps into a framework. As well as guiding decision-making, the framework can also provide the structure for a policy document to ensure that all agencies have a shared understanding of the key elements of the response. The proposed framework is intended to make as few assumptions as possible about the causative organism.

A pandemic strategy is a high-level approach that articulates the direction of travel of the response, whereas control measures are the actions taken to implement the response (COVID-19 Public Health Response Strategy Team 2020a). An evaluation of emerging evidence about the pandemic informs selection of an appropriate strategy with clearly defined aims and objectives, and the evidence and strategy together inform selection of appropriate control measures.

A pandemic response, once determined, is not set in stone. Although the goal of the response and the principles that guide it will remain consistent, the strategy may shift over the course of the pandemic as circumstances change, while control measures may change rapidly as new interventions become available and systems become operational.

The process of defining a response therefore needs to be an iterative one, with new evidence constantly shaping and refining the strategy and control measures. Without a robust system for evidence review, there is a risk of path dependency in which a decision is made at one time point and further attention is directed solely at improving performance, regardless of the changing context.

Articulation of guiding principles and values to determine the goal

An essential first action is to state the principles and values that underlie all the decisions in the pandemic response. Public health principles must uphold Te Tiriti o Waitangi and align with other values in the health system (COVID-19 Public Health Response Strategy Team 2020b). The principles shape decisions by articulating a goal for the pandemic strategy (e.g. ‘To implement an effective and equitable response’). These principles also guide how decisions are made, for example, whose voices count in determining the choice of strategy or control measures.

Because values whether stated or unstated shape highly consequential decisions for population health and wellbeing, this step must not be omitted even in an emergency situation. High-urgency decision-making must be founded on strong principles in order to resist external pressures to select an expedient but potentially harmful and inequitable course of action. Much of this ground work can be conducted as part of pre-pandemic planning and the key principles and values are likely to be reasonably stable and enduring. As with many elements in the pandemic planning process, regular exercises can help to familiarise staff with them, and identify areas that need further refinement and updating.

Evidence review in an emerging pandemic: what matters for strategy design?

Four broad types of evidence about a pandemic and the infecting agent need to be established rapidly and revised as new information becomes available:

• Transmissibility and key infection dynamics

• Severity and likely population impact

• Controllability and resource considerations

• Certainty of knowledge.

These four types of evidence are essential in guiding strategic decisions and particularising the strategy, including the timing and intensity of control measures, indicators of success or failure of the strategy, and exit pathways. They can also be used to measure and report on equity in the response, ensuring that people with different levels of advantage have access to the approaches and resources they need for equitable health outcomes (Ministry of Health 2020). These categories of evidence are discussed below ().

Defining and quantifying the pandemic strategy, aims and objectives

Identifying the broad strategy and aims

Based on the evidence review, the agency responsible for managing the pandemic will need to choose a strategy and associated aims. The options are broadly along a continuum (Baker, Wilson, and Blakely 2020) from:

1. Mitigation, a form of control that accepts transmission at a predetermined, manageable level, e.g. to avoid overwhelming the health system in an influenza pandemic;

2. Suppression, a form of control that aims to keep transmission at a low level to minimise adverse health effects, as for HIV/AIDS;

3. Elimination, which aims for zero community transmission of a pathogen (and can become eradication if extended to the global level) (Klepac et al. 2013). This strategy includes ‘exclusion’ where border controls are applied so effectively that the pathogen never transmits within a particular jurisdiction.

These strategic choices have been used by epidemiologists to define infection control aims for a wide range of pathogens (Prichard et al. 2012; Thomas 2019). Eradication, by definition requires a global effort and is extremely difficult to achieve so is not generally a meaningful aim for a single country or jurisdiction, particularly during a pandemic ().

Figure 1. Strategic choices for pandemic response. Based on: Dowdle, MMWR Supple. December 1999 / 48 (SU01);23 7.

Aims are quantified to assess the success or failure of the strategy (De Serres et al. 2000). For example, elimination of Covid-19 in Aotearoa NZ has been quantified as one month of no new notified cases of Covid-19 (to give 95% certainty of elimination (Wilson, Parry, et al. 2020)). A strategy is defined by its aims and can only succeed in so far as it achieves those aims (even though it may fail in one or more objectives). For this reason, the aims of a strategy will remain stable over the life of the strategy. Ongoing surveillance will be required to measure the success of the strategy’s aims, because failure (or impending failure) should trigger a reassessment of the response and potentially, a transition to a different strategy.

Identifying appropriate and effective control measures/interventions

Control measures are the specific interventions (e.g. active case finding, contact tracing, quarantine, school closures) that are needed to achieve the objectives and deliver the aims of the strategy. The timing, intensity, and mix of control measures will vary between and within strategies: the zero-tolerance approach of elimination, for example, requires active control in the presence of low transmission, while mitigation and suppression efforts will more closely correlate with transmission levels. These factors also depend on the impact, transmission characteristics, and severity profile of the causative organism, as outlined above.

demonstrates the intervention logic common to all outbreak control. The reproduction number (R) is the average number of secondary cases generated by each case (see for more information). The control measures work together to interrupt transmission and drive the value of R down.

Figure 2. Intervention logic for outbreak control, showing the mechanisms of action of common control measures. (Adapted from a diagram originally developed by one of us [AK] for the Ministry of Health’s Elimination Strategy report (COVID-19 Public Health Response Strategy Team 2020a))

The principles of control work for any infectious disease including those spread by non-respiratory routes (National HIV and AIDS Forum 2017), although they are most straightforward for human-to-human transmission (King 2009). This diagram shows the control measures organised by the mechanism of action, but they are implemented in terms of the strategy objective that they contribute to (e.g. border control or case and contact management), as seen in .

Some control measures are used for more than one type of objective. Quarantine (a measure that reduces contact rate between susceptibles and infected (Wilson, Kvalsvig, and Baker 2020)) is used in border control, in the case and contact management system, and as a population-level intervention – with lockdown effectively acting as a quarantine measure for the whole population.

For maximum effectiveness, implementation of control measures should be carefully aligned to the transmission characteristics of the organism (). For example, an understanding of transmission in children is essential for decision-making around school closures (Kvalsvig, Wilson, D’Souza, et al. 2020).

Ensure adequate and appropriate infrastructure

The effectiveness of the pandemic response depends on the quality of the infrastructure underlying both design and implementation. Infrastructure to support the pandemic response derives not only from health and other Government agencies, but from multiple entities including academic institutions, community organisations, research funders, and the population at risk. Effective coordination and communication is therefore essential.

A well-trained and rapidly expandable public health workforce is required to identify an optimal mix of interventions and ensure that interventions are implemented in an effective, efficient, and sustainable way. A coordinated response also requires excellent situational awareness across all agencies and in the general population, with extensive and integrated systems for collecting, synthesising, and communicating the evidence. Community leaders are a vital link in the communication network and provision needs to be made for regular hui, kōrero, and educational outreach as new evidence comes to light.

Thus, a key task in developing the response is to identify and remedy infrastructure gaps, also looking ahead to determine capacity and scalability in the near- to medium-term as the pandemic evolves.

Review and adaptation

The evidence review and decisions outlined in the framework will not take place just once; instead, they will need regular review. A key driver for review already mentioned in an earlier section is the need to have ongoing assurance that the strategy is meeting its stated (and quantified) aims.

Regular review is also necessary to reassess changing evidence and resources, and to consider changes to the response prompted by progression of the epidemic curve itself. The ‘endgame’ of elimination, for example, may be very different from the middle game, as the epidemiology, control measures, and knowledge gaps change (Klepac et al. 2013).

The Covid-19 response evolved considerably between March and October 2020. Some important strategic and operational changes included:

• The pivot from ‘Flattening the curve’ to elimination during March (Baker, Kvalsvig, Verrall, et al. 2020)

• A greatly expanded manual contact tracing system (and progress towards technology-based tracing) (Verrall 2020)

• Adoption of recommended and mandated use of masks (face coverings) (Kvalsvig, Wilson, Chan, et al. 2020)

• Operational use of genomic sequencing to aid case and contact management (Geoghegan et al. 2020).

These changes allowed Aotearoa NZ to manage its second outbreak (the Auckland August cluster) without triggering Alert Level 4. Management of the outbreak was also helped by the fact that the country was in a state of elimination at the start of the outbreak, allowing the public health response to direct a large amount of resource to management of the outbreak.

As Aotearoa NZ approaches the anniversary of the arrival of Covid-19 in the country on 26 February 2020 the focus of objectives has justifiably shifted to managing the risk of imported disease (Kvalsvig, Summers et al. 2020). This need has intensified with the increasing intensity of the pandemic globally, and the emergence of more infectious variants (Lauring and Hodcraft 2021). A big focus has been the need to shift from a ‘one size fits all’ to a ‘risk based’ approach to managing borders where different levels of control are applied to passengers depending on their country of origin and likely level of infection (Wilson and Baker 2021). This shift can be expressed as a move to a ‘traffic lights’ approach (Wilson and Baker 2020).

The response will continue to evolve, with the development and roll-out of Covid-19 vaccines potentially triggering the next major change in approach. There are widely different future scenarios for how Covid-19 will be best managed at the national, regional and global levels. The availability of highly effective vaccines is likely to make national and regional elimination possible, and even global eradication might be feasible (Baker, Wilson, and Blakely 2020). However, it is also possible that following widespread vaccination, SARS-CoV-2 might become an endemic circulating coronavirus where population immunity may be driven by the endemic presence of SARS-CoV-2 rather than regular vaccination (Veldhoen and Simas 2021).

Building scenarios and strategies only on the basis of well-known pathogens risks failing to exploit all possible measures to slow transmission of the Covid-19 virus, reduce disease and save lives.

WHO-China Joint Mission (World Health Organization 2020)

An inquiry to review the Covid-19 response and identify lessons learned

A major advantage of Aotearoa NZ’s elimination approach and the resulting high level of Covid-19 control is that the key actors have opportunities not afforded elsewhere to document and reflect on the response. We have previously called for an inquiry to examine the early phases of the Covid-19 response (Baker, Kvalsvig, and Wilson 2020). This inquiry would have the dual function of improving the current response and identifying key areas for action in preparing for the next pandemic. The inquiry should be held early to preserve valuable and detailed ‘institutional’ (i.e., otherwise undocumented) memories of strengths and difficulties in the response. Another key focus would be to learn from the highly effective community responses that were implemented around the country, in particular by Māori organisations, for example to support food security and connect vulnerable whānau to health and social resources.

Revision of the existing pandemic plan

Likewise, revision of the existing pandemic plan should not wait until the Covid-19 pandemic is over, as the next pandemic could already be in train. In this paper we have outlined a framework to guide development of a response to emergence of a new pandemic in Aotearoa NZ, taking a systematic approach to identify the most appropriate set of control measures for the pathogen and the circumstances. The approach outlined in this paper is founded on well-established principles that have been used to control, eliminate, and eradicate a wide variety of infectious diseases.

Creation of a national public health agency to oversee development of national public health infrastructure and workforce and deliver the pandemic response

One of the most valuable lessons we can draw from the Covid-19 experience in Aotearoa NZ is the importance of developing an agile response that is not constrained by preconceptions about what is and is not feasible to achieve. Such a response requires experience and expertise to synthesise emerging evidence and to make decisions in the presence of a high degree of uncertainty. The response also requires a public health workforce that is familiar with basic principles and has the skills to support decision-making through modelling, evidence review, and other activities. The composition of this workforce should reflect the population of Aotearoa NZ to ensure that decision processes are inclusive and equitable. A key early priority in the establishment of a new public health agency will be to articulate the values that will guide both day-to-day operation and the critical decisions that need to be made in a public health emergency.

Decades of under-funding have resulted in a small and overstretched public health workforce with the result that the contribution of pandemic epidemiology expertise to the Covid-19 response has operated largely on donated time. There is an urgent need to develop and sustain a robust and diverse public health infrastructure and workforce. This workforce will need to monitor emerging evidence about pandemic control to ensure that Aotearoa NZ’s pandemic plan always reflects current knowledge and best practice.

The Covid-19 crisis is a stark reminder of the need to invest in pandemic planning and the associated infrastructure. We can learn from our own successes and failures during the current response. It is also useful to look at countries across the globe that are succeeding and failing in their responses. One example of success is Taiwan, that has sustained long-term Covid-19 elimination without the need for a lockdown, resulting in minimal loss of life and economic harm. A key point of difference is that it has well-established public health agencies focussed on pandemic management (Summers et al. 2020). These examples both within and outside Aotearoa NZ emphasise the need to learn, and continue to learn, how to stay ahead of an inevitable future pandemic threat.