COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study

COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study(external link), was published in the Lancet Public Health. In the study, the researchers unpacked and analysed how New Zealand’s science-informed public health measures managed the first wave of COVID-19.

The team, including national infectious disease epidemiology and public health expertise from ESR, Massey and Otago Universities, Epi-interactive and the Ministry of Health,  performed a descriptive epidemiological study of all confirmed and probable cases and all patients tested for the virus in New Zealand to 13 May 2020.

The study used national COVID-19 case and testing datasets, EpiSurv and Éclair, to comprehensively describe New Zealand’s initial public health response to COVID-19 and impacts on the burden of COVID-19 initially experienced by New Zealanders.

To the author’s knowledge, this is the first study which assesses the impacts of national or sub-national public health response escalation and de-escalation decisions on the distribution, transmission patterns and severity of COVID-19, and the attainment of an explicit national goal of COVID-19 elimination.

The researchers looked at the timing of New Zealand’s implementation of graduated, risk-informed national public health measures, which were ultimately aimed at disease elimination. As evidence emerged, New Zealand moved from a response guided by national influenza pandemic planning to a COVID-19-tailored approach focusing on suppression (stamping COVID-19 out) over mitigation (slowing COVID-19 down), with a goal of COVID-19 elimination to reach very low or zero COVID-19 incidence. They found that the speed and intensity of the national response to limit community spread was unprecedented internationally. Integral to the response was decisive leadership, effective communication and community engagement, and the responsiveness of New Zealand’s healthcare system, to ramp up testing, contact tracing and the reprioritisation of other services.

The authors concluded that the actions taken by New Zealand support the WHO recommendations for timely decisive national leadership and for evidence-informed, risk-based escalation and de-escalation decisions combining rigorous case detection, isolation, contact tracing and quarantine measures, with population education and engagement.

The study outlines that further surveillance and research are needed to understand the cost-benefits, particularly the indirect population health and social impacts, of the New Zealand response.

Study by numbers:

  • There were 1503 cases, 95 hospitalisations and 22 COVID-19 (1·5%) deaths to 13 May. This represents one of the lowest cumulative case counts, and rates of COVID-19 and mortality from it, reported internationally during the first wave.
  • The estimated average daily case infection rate peaked at 8·8 cases per million per day during the ten-day period of rapid response escalation to Level 4, declining markedly (a 62% reduction in infection rate) from the start of Level 4 lockdown and progressively thereafter.
  • Most cases were linked to importation (69%), tending to be younger adults, European, and of higher socioeconomic status. More severe disease outcomes were associated with locally acquired infection, older age, Aged Residential Care residency, and Pacific and Asian ethnicities.
  • 702 (47%) cases were linked to 34 outbreaks.

Times from case illness onset to notification and isolation progressively decreased and testing increased over the study period, with few disparities and increasing coverage of females, Māori, Pacific peoples, and lower socio-economic groups.