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On 28 February 2020, Aotearoa New Zealand recorded its first case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, causing coronavirus disease 2019 (COVID-19) in a traveller returned from the Middle East. A rapid and sustained public health response ensued, including contact tracing, countrywide lockdown and government-managed quarantine of international travellers.[[1,2]] New Zealand successfully eliminated community COVID-19 transmission by May 2020, diverging from most other OECD countries and resulting in both low case numbers and fatalities.[[1]] Further community outbreaks occurred August to September 2020 and in February 2021, again with successful elimination. However, in August 2021, the increased transmissibility of the COVID-19 Delta variant resulted in total case notifications rising across the Auckland region, despite high vaccination rates.[[3]] With relaxation of public health measures, including travel restrictions, it is likely SARS-CoV-2 will eventually become endemic across New Zealand. Understanding patient characteristics, outcomes and resourcing during the early waves may help plan for future outbreaks and this transition to endemic disease.

Whilst knowledge regarding patient risk factors, clinical progression and treatments for COVID-19 in hospitalised patients has progressed rapidly from international large-scale studies,[[4]] there is a paucity of local data. Healthcare in New Zealand is predominately public-funded and is currently delivered by twenty district health boards (DHBs). Sixteen percent of the population live rurally[[5]] and 10% are served by rural hospitals[[6]] which may have limited staffing and resourcing. New Zealand has a diverse ethnic make-up with its population identifying as NZ European (70.2%), Māori (Indigenous peoples) (16.5%), Asian (15.1%), Pasifika (8.1%) and Middle Eastern, Latin American and African (MELAA) (1.5%).[[5]] Global data have indicated disproportionate mortality amongst ethnic minority groups with COVID-19[[7, 8]] and it is recognised that Māori and Pasifika are more likely to contract, and be hospitalised, with infectious diseases[[9]] including COVID-19.[[10]]

To characterise local factors associated with adverse outcomes in hospitalised COVID-19 patients in New Zealand, the multi-centre COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION) study was established in April 2020. Additional study outcomes included an analysis of key hospital resources usage such as oxygen, length of stay (LOS) and requirement for intensive or high dependency care. The majority of data to date were collected from patients admitted to hospital during the early community waves, although further data collection and analyses are planned. Here, we present a descriptive review of patients hospitalised with COVID-19 in New Zealand from 26 February to 5 October 2020, encompassing from the first reported case in New Zealand until the end of the second wave of community transmission.

Methods

We conducted a multi-centre retrospective cohort study. Eleven DHBs across New Zealand were enrolled including Auckland, Bay of Plenty, Canterbury, Capital and Coast, Counties Manukau, Hutt Valley, Lakes, MidCentral, Southern, Waikato and Waitematā. Patients of any age admitted to participating DHBs with a primary clinical diagnosis of COVID-19, based on contemporaneous Ministry of Health definitions,[[11]] were identified by site investigators and included for analysis. We enrolled both confirmed COVID-19 cases, i.e., those with symptomatology and positive SARS-CoV-2 polymerase chain reaction (PCR) testing and probable cases. Probable cases were defined as a symptomatic close contact of a confirmed case (epi-link), or a case that met the clinical criteria, in whom other aetiologies explaining the clinical presentation had been excluded, and where laboratory testing was either suggestive of SARS-CoV-2 or inconclusive. Patients with COVID-19 hospitalised for less than six hours or admitted primarily for an unrelated diagnosis were excluded.

Data were extracted from individual patient records by investigators. Patients identifying as more than one ethnic group were analysed as a single ethnicity, prioritised in the order of Māori, Pasifika, Asian then NZ European/Other.[[3]] A returned traveller was defined as having travelled internationally within the 14 days preceding symptom onset. Presenting symptoms related to self-reported symptomatology during or prior to hospital admission. Blood and biochemical results were obtained from the first laboratory tests taken during admission. LOS was calculated from the date of admission to the date of hospital discharge or death and included time spent in inpatient rehabilitation facilities. Inpatient mortality was defined as death during hospital admission. The presence or absence of some patient characteristics were variably documented in the clinical notes. Therefore, data are reported as the number of patients with a characteristic, over the denominator of patients for whom this information was available.  

De-identified data were collected by investigators and uploaded to a secure online database. Descriptive analyses were performed using pooled data. We performed bivariate logistic regression of a composite “severe outcome”, defined as admission to intensive/high dependency care (ICU/HDU) or inpatient death, against patient age, ethnicity and selected co-morbidities. Statistical analysis was performed in Stata 16.0 (StataCorp, College Station, TX, United States). Ethical approval for this study was obtained from the New Zealand Health and Disability Ethics Committee (reference: 20/NTB/72/AM02) and local approvals were obtained at each participating site.

Results

Eighty-four patients were identified from the 26 February to 5 October 2020 with data submitted from eight of the eleven participating district health boards (DHBs). The majority were hospitalised in three Auckland DHBs, Auckland, Counties-Manukau and Waitemata (n=56, 67%) (Figure 1). Nine patients (11%) were healthcare workers and four (5%) were pregnant. Seventeen patients (20%) were returned travellers. A positive SARS-CoV-2 test was collected from 66/76 (87%) patients during admission. The remainder had either a positive community test prior to admission or fulfilled the ‘probable’ case criteria.

Figure 1: Proportion of patients admitted with COVID-19, by District Health Board, 2020.

Demographics and Co-morbidities

Forty-one patients (49%) were men, and the median age was 58 years [n=83, interquartile range [IQR] 41.7–70.3 years]. The most common age decile was 50–59 years (19/83, 23%) (Table 1). Sixteen patients (19%) were under 40 years. The only child in the cohort (≤18 years old) was a 2-month-old infant. By ethnicity, 38 (45%) patients identified as NZ European; 19 (23%) Pasifika; 13 (15%) as Māori; 12 (14%) as Asian and 2 (2%) as Other (Table 2). Māori were the youngest group admitted, with a median age of 45 years [IQR: 42–58 years]. NZ European/Other were the oldest, median age 63 years [IQR: 51–78 years]. Forty-eight (57%) patients had at least one reported pre-existing co-morbidity. Metabolic co-morbidities included chronic cardiac disease (12/82, 15%), hypertension (26/82, 32%), diabetes (18/81, 22%) and obesity (16/66, 24%) (Table 1). Twenty-five (32%) of 79 patients were ex-smokers and 2 (3%) were current smokers.

A record of a composite severe outcome was available in 83/84 patients, with 19/83 (23%) dying or admitted to ICU/HDU. When correlated against a severe outcome of death or ICU/HDU admission, none of age, ethnicity or co-morbidities were shown to confer a worse outcome (Table 1). Māori had the highest proportion admitted to ICU/HDU (38%) (Table 2). Those identified as NZ European/Other had the highest in-hospital mortality (21%) but were also the oldest (mean=64 years [IQR: 51–80 years]) with the lowest rate of ICU/HDU admission (8%). When adjusted for age, the adjusted odds ratio (aOR) of a composite severe outcome for Māori was 3.7 (95% Confidence Interval (CI): 0.93–14.7, p=0.06) when compared to Non-Māori/Non-Pasifika. For Pasifika the aOR was 0.58 (95% CI: 0.14–2.29, p=0.44).

View Tables 1 & 2.

Clinical features

Patients reported a median of seven days of symptoms [IQR: 4–10 days] prior to presentation. The most common were cough (66/83, 80%) and shortness of breath (58/84, 69%). Systemic symptoms including fever (56/84, 67%), myalgia (28/66, 42%) and fatigue (48/75, 64%) were frequently described. Gastrointestinal symptoms including abdominal pain (9/73, 12%), nausea or vomiting (12/72, 17%) and diarrhoea (12/71, 17%) were also reported. On admission, 23/71 (32%) had a temperature ≥38°C. The median heart rate (90 beats per minute [IQR: 78–101bpm]), respiratory rate (20 respirations per minute [IQR: 18–25resps/min]) and oxygen saturations (96% [IQR: 94–98%]) on arrival were generally within normal ranges (Table 3). Oxygen saturations ≤92% were recorded in 10/81 (12%) patients on admission. View Table 3.

Median measurements of blood count parameters at admission, including liver function tests and electrolytes, were predominately in normal ranges although median lactate dehydrogenase (LDH) (360U/L [IQR: 313–471U/L]), C-reactive protein (41mg/L [IQR: 8–96mg/L]), D-dimer (670ng/mL [IQR: 300–950ng/mL]) and ferritin (925ug/L [IQR: 304–1394ug/L]) were noted as being elevated (Table 3). Admission chest x-rays showed infiltrates in 46/76 (61%) patients.

More than half of patients (46/83, 55%) hospitalised with COVID-19 experienced a complication of their illness (Table 4). A cardiac arrhythmia was documented in 6/80 patients (8%); 6/82 patients (7%) developed bacteraemia, 3/83 patients (4%) had bleeding complications, and 1/83 (1%) had a pulmonary embolus. Regarding therapeutics, 18/82 (22%) patients received oral or intravenous (IV) corticosteroids during admission, 48/82 (59%) received an antibiotic and 2/83 (2%) an antiviral (1 entecavir, 1 unknown). During hospital admission, 42/82 patients (51%) required oxygen with 18/82 (22%) requiring high-flow (≥5L/min). The median duration of oxygen usage was five days [IQR: 2–9 days].

View Table 4.

Outcomes

The median length of hospital stay (LOS) was four days [IQR: 2–15 days]. The mean LOS was nine days [standard deviation=11 days]. Nineteen patients (19/82, 23%) were admitted for more than 14 days (Figure 2). Twelve patients (12/83, 14%) were admitted to ICU/HDU. Six (7%) required invasive ventilation for a median duration of 15 days [IQR: 13–15 days]. No patients required extracorporeal support. Two (2%) underwent haemodialysis. The median duration of ICU/HDU admission was 10 days [IQR: 2–15 days].

In-hospital death occurred in 10 patients (10/83, 12%). The median age at death was 82.9 years [IQR: 72.8–94.4 years] and the median admission length prior to death was 14 days [IQR: 7–21 days]. Seven (70%) of these deaths occurred in patients not admitted to ICU/HDU.

Figure 2: Length of stay of patients hospitalised with COVID-19 February to October, 2020

Discussion

Here we present early data from the COHESION study: a retrospective, multi-centre study reviewing the demographics and outcomes of patients hospitalised with COVID-19 in New Zealand from the early waves of the pandemic. Despite a comparatively low population prevalence of COVID-19, hospitalised patients still required significant healthcare resourcing with high rates of oxygen use, prolonged admissions and multiple inpatient complications. In-hospital mortality was considerable. Deceased patients were elderly and most died without admission to ICU/HDU; however, severe outcomes occurred across the age spectrum.

During the time period studied, 1866 COVID-19 cases (38 per 100,000 population) and around 120 hospitalisations were reported in New Zealand.[[10]] Therefore, our study captured 70% of those admitted with COVID-19 and can be considered a good representation of hospitalisations nationally. Similar to international findings, many hospitalised patients were elderly;[[4, 12]] however, the median age of our cohort was younger than comparable studies.[[12]] This may reflect many of New Zealand’s early COVID-19 cases occurring as imported infections in returned travellers who tended to be younger, predominately European and of high socioeconomic status.[[1, 13]] Co-morbidities were common among those hospitalised. Although we did not collect data on the effect of COVID-19 on control of co-morbidities such as diabetes, our study emphasises the complex healthcare needs of COVID-19 patients that extend beyond direct effects of the virus.

Patients hospitalised with COVID-19 in New Zealand experienced a high prevalence of complications, notably acute kidney injury, delirium and cardiac arrhythmia. There was a discrepancy between the prescription of antibacterial medication and the prevalence of bacteraemia. While bacteraemia is present in only a minority of bacterial infections that require treatment, current literature suggests that super-added bacterial infection with COVID-19 is probably less common than in other viral pandemics.[[14]] Due to the importance of antimicrobial stewardship in combatting bacterial antimicrobial resistance, ongoing work to identify which patients with COVID-19 also have bacterial superinfection is critical.

The proportion of patients who died in our study was approximately half that reported in the United Kingdom (26%),[[4]] but comparable to a large multi-centre study in the USA (14% with a further 3% discharged to hospice).[[15]] Of note, both these and our study were conducted prior to vaccination and the widespread usage of dexamethasone, remdesivir and tocilizumab, repurposed agents which have been shown to improve outcomes in hospitalised patients with COVID-19. Only small numbers in our cohort received anti-viral agents, immune modulators or corticosteroids, in keeping with international practice at the time. It is notable that only a minority of patients who died during hospital admission received ICU/HDU treatment suggesting either that they died rapidly, or would not have benefited from more invasive interventions offered by ICU/HDU such as ventilation, inotrope support or renal replacement therapy. The older age of this cohort, and duration of hospital stay prior to death appears to suggest the latter. An important implication of this finding is that planning and resources are needed to provide palliative care for patients dying of COVID-19.

Despite low case numbers in the early waves of the pandemic, COVID-19 hospitalisations absorbed substantial healthcare resources with healthcare workers being a high proportion of those hospitalised. There was significant variability between individual patient’s lengths of hospital stay, with prolonged admissions in a substantial minority. This is comparable to the international literature[[16]] and highlights the importance of structures to support holistic care for those with long hospital stays. The proportion of patients admitted to ICU/HDU (14%) was similar to that reported from the UK (17%),[[4]] with many requiring invasive ventilation and resource-intensive proning. The ICU bed capacity of New Zealand is 4.6/100,000 people, lower than comparable healthcare systems,[[17]] with further addition of bed capacity likely limited by the availability of trained nursing staff.[[18]] If a similar proportion of hospitalised cases require ICU admission in future waves of the pandemic, there is a risk the ICU capacity of New Zealand would be exceeded. Strategies to mitigate this could include increasing ICU staffing and bed capacity, and optimising community and ward-based care.

This analysis has not identified any risk factors for death or ICU/HDU admission among those admitted to hospital but are compatible with international studies identifying age as the most important risk factor.[[4]] The small sample size of our study means it is underpowered to detect all but the largest risk factors. Although we did not identify Māori or Pasifika ethnicity as being associated with an increased risk of death or ICU/HDU admission in our analysis, this remains an important association to monitor. We used a prioritised ethnic system, assigning a single ethnicity for the purpose of analysis. It is therefore possible that the impact on certain groups, particularly Pasifika, may have been underestimated. Previous work by Steyn et al over a time period similar to our study, identified Māori and Pasifika with COVID-19 were at 2.5–3 times the risk of hospitalisation when compared to NZ European/Other ethnic groups.[[10]] The authors also noted a younger age at admission and longer lengths of hospital stay in Māori and Pasifika, which is consistent with our findings.

Our study does have limitations that influence interpretation. As a retrospective study, complete data could not be obtained for all patients. Data collection was concentrated in tertiary urban centres and caution should be used when generalising to smaller or rural hospitals. The study was not adequately powered to assess risk factors for severe outcomes, however the absence of statistically significant risk associated with ethnicity, age or co-morbidities does not preclude an important relationship. Data collection is ongoing and we hope this will be addressed in future analyses. Finally, since the study end date, there has been considerable progression of knowledge regarding transmission, treatment and progression of COVID-19, as well as emergent viral strains and the development of effective vaccines. Whilst these factors will inevitably alter the demographics and outcomes of those affected, we have identified signals for ongoing research. Further data collection for COHESION will be able to utilise our findings to develop a comparison of the demographics and clinical progression of those affected in early and later outbreaks.

Conclusion

This observational study describes the demographics, clinical course and outcomes of patients hospitalised with COVID-19 in New Zealand during 2020. There was a high proportion of patients who died, particularly while receiving ward-based care, as well as substantial utilisation of ward beds, ICU/HDU beds and oxygen. Our study highlights the high prevalence of co-morbidities that increase complexity of care, and diversity of age and ethnicity. This emphasises not only the need for care which is person- and- whānau-centred and culturally safe during hospitalisation, but also in the community. Whilst further work is required to identify local patient risk factors for progression to severe COVID-19, our preliminary data identify areas of priority for healthcare resourcing to optimise resilience of the New Zealand healthcare system in preparation for endemic COVID-19.

Summary

Abstract

Aim

As New Zealand transitions towards endemic SARS-CoV-2, understanding patient factors predicting severity, as well as hospital resourcing requirements will be essential for future planning.

Method

We retrospectively enrolled patients hospitalised with COVID-19 from 26 February to 5 October 2020 as part of the COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION). Data on demographics, clinical course and outcomes were collected and analysed as a descriptive case series.

Results

Eighty-four patients were identified across eight district health boards. Forty-one (49%) were male. The median age was 58 years [IQR: 41.7–70.3 years]. By ethnicity, hospitalisations included 38 NZ European (45%), 19 Pasifika (23%), 13 Māori (15%), 12 Asian (14%) and 2 Other (2%). Pre-existing co-morbidities included hypertension (26/82, 32%), obesity (16/66, 24%) and diabetes (18/81, 22%). The median length of stay was four days [IQR: 2–15 days]. Twelve patients (12/83, 14%) were admitted to an intensive care unit or high dependency unit (ICU/HDU). Ten (10/83, 12%) patients died in hospital of whom seven (70%) were not admitted to ICU/HDU; the median age at death was 83 years.

Conclusion

Despite initially low case numbers in New Zealand during 2020, hospitalisation with COVID-19 was associated with a high mortality and hospital resource requirements.

Author Information

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. Lydia Foley: Department of Medicine, University of Otago, Christchurch, New Zealand. Juliette Phillipson: Department of Medicine, University of Otago, Christchurch, New Zealand. Sandy Slow: Department of Medicine, University of Otago, Christchurch, New Zealand. Malina Storer: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Jonathan Williman: Department of Population Health, University of Otago, Christchurch, New Zealand. Richard Beasley: Medical Research Institute of New Zealand, Wellington, New Zealand. Hasan Bhally: Infectious Diseases Department, Waitematā District Health Board, Auckland, New Zealand. Cat L Chang: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Jack Dummer: Department of Medicine, University of Otago, Dunedin, New Zealand; Respiratory Medicine Department, Southern District Health Board, Dunedin, New Zealand. Michael Epton: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Mary Furniss: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Kathryn Gracie: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Robert J Hancox: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Thomas Hills: Medical Research Institute of New Zealand, Wellington, New Zealand; Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Stephen Hogg: Infectious Diseases Department, Hutt Valley District Health Board, Hutt Valley, New Zealand. Sandra Hotu: Respiratory Medicine Department, Auckland District Health Board, Auckland, New Zealand. Nethmi Kearns: Medical Research Institute of New Zealand, Wellington, New Zealand. Susan Morpeth: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. David Murdoch: Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand. Nigel Raymond: Infectious Diseases Department, Capital and Coast District Health Board, Wellington, New Zealand. Stephen Ritchie: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Conroy Wong: Respiratory Medicine Department, Counties Manukau-District Health Board, Auckland, New Zealand. Michael J Maze: Department of Medicine, University of Otago, Christchurch, New Zealand; Respiratory Medicine Department, Canterbury District Health Board, New Zealand.

Acknowledgements

Correspondence

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand.

Correspondence Email

aliya.bryce@doctors.org.uk

Competing Interests

Nil.

1) Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study. Lancet Public Health. 2020 Nov;5(11):e612-e623.

2) Baker MG, Wilson N, Anglemyer A. Successful elimination of Covid-19 transmission in New Zealand. N Engl J Med. 2020 Aug 20;383(8):e56.

3) New Zealand Ministry of Health [Website]. COVID-19: Case demographics. Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-case-demographics.

4) Docherty AB, Harrison EM, Green CA, et al; ISARIC4C investigators. Features of 20 133 UK patients in hospital with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol: prospective observational cohort study. BMJ. 2020 May 22;369:m1985.

5) Environmental Health Intelligence New Zealand [Website]. Population vulnerability. Available from: https://www.ehinz.ac.nz/indicators/population-vulnerability/

6) Janes R. Rural hospitals in New Zealand. N Z Med J. 1999 Aug 13;112(1093):297-9.

7) Mathur R, Rentsch CT, Morton CE, et al; OpenSAFELY Collaborative. Ethnic differences in SARS-CoV-2 infection and COVID-19-related hospitalisation, intensive care unit admission, and death in 17 million adults in England: an observational cohort study using the OpenSAFELY platform. Lancet. 2021 May 8;397(10286):1711-1724.

8) Tai DBG, Shah A, Doubeni CA, et al. The disproportionate impact of COVID-19 on racial and ethnic minorities in the United States. Clin Infect Dis. 2021 Feb 16;72(4):703-706.

9) Baker M, Barnard LT, Shang J, et al. Close-contact infectious diseases in New Zealand: trends and ethnic inequalities in hospitalisations, 1989 to 2008. A report prepared for the Māori Health Directorate, Ministry of Health. Wellington: University of Otago, 2010. Available from: www.healthyhousing.org.nz.

10) Steyn N, Binny RN, Hannah K, et al. Māori and Pacific people in New Zealand have a higher risk of hospitalisation for COVID-19. N Z Med J. 2021 Jul 9;134(1538):28-43.

11) New Zealand Ministry of Health [Website]. Case definition and clinical testing guidelines for COVID-19. Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-information-health-professionals/case-definition-and-clinical-testing-guidelines-covid-19.

12) Kim L, Garg S, O'Halloran A, et al. Risk Factors for intensive care unit admission and in-hospital mortality among hospitalized adults identified through the US Coronavirus Disease 2019 (COVID-19)-Associated Hospitalization Surveillance Network (COVID-NET). Clin Infect Dis. 2021 May 4;72(9): e206-e214.

13) Kearns N, Eathorne A, Luff T, et al. Clinical and epidemiological characteristics of COVID-19 in Wellington, New Zealand: a retrospective, observational study. N Z Med J. 2021 Sep 17;134(1542):38-49.

14) Garcia-Vidal C, Sanjuan G, Moreno-García E, et al. Incidence of co-infections and superinfections in hospitalized patients with COVID-19: a retrospective cohort study. Clin Microbiol Infect. 2021 Jan;27(1):83-88.

15) Nguyen NT, Chinn J, Nahmias J, et al. Outcomes and Mortality Among Adults Hospitalized With COVID-19 at US Medical Centers. JAMA Netw Open. 2021 Mar 1;4(3):e210417.

16) Rees EM, Nightingale ES, Jafari Y, et al. COVID-19 length of hospital stay: a systematic review and data synthesis. BMC Med. 2020 Sep 3;18(1):270.

17) Betteridge T, Henderson S. Intensive care in New Zealand: time for a national network. N Z Med J. 2020 Aug 21;133(1520):148-149.

18) Young PJ, Psirides A, Streat S. New Zealand's staffed ICU bed capacity and COVID-19 surge capacity. N Z Med J. 2021 Nov 12;134(1545):8-10.

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On 28 February 2020, Aotearoa New Zealand recorded its first case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, causing coronavirus disease 2019 (COVID-19) in a traveller returned from the Middle East. A rapid and sustained public health response ensued, including contact tracing, countrywide lockdown and government-managed quarantine of international travellers.[[1,2]] New Zealand successfully eliminated community COVID-19 transmission by May 2020, diverging from most other OECD countries and resulting in both low case numbers and fatalities.[[1]] Further community outbreaks occurred August to September 2020 and in February 2021, again with successful elimination. However, in August 2021, the increased transmissibility of the COVID-19 Delta variant resulted in total case notifications rising across the Auckland region, despite high vaccination rates.[[3]] With relaxation of public health measures, including travel restrictions, it is likely SARS-CoV-2 will eventually become endemic across New Zealand. Understanding patient characteristics, outcomes and resourcing during the early waves may help plan for future outbreaks and this transition to endemic disease.

Whilst knowledge regarding patient risk factors, clinical progression and treatments for COVID-19 in hospitalised patients has progressed rapidly from international large-scale studies,[[4]] there is a paucity of local data. Healthcare in New Zealand is predominately public-funded and is currently delivered by twenty district health boards (DHBs). Sixteen percent of the population live rurally[[5]] and 10% are served by rural hospitals[[6]] which may have limited staffing and resourcing. New Zealand has a diverse ethnic make-up with its population identifying as NZ European (70.2%), Māori (Indigenous peoples) (16.5%), Asian (15.1%), Pasifika (8.1%) and Middle Eastern, Latin American and African (MELAA) (1.5%).[[5]] Global data have indicated disproportionate mortality amongst ethnic minority groups with COVID-19[[7, 8]] and it is recognised that Māori and Pasifika are more likely to contract, and be hospitalised, with infectious diseases[[9]] including COVID-19.[[10]]

To characterise local factors associated with adverse outcomes in hospitalised COVID-19 patients in New Zealand, the multi-centre COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION) study was established in April 2020. Additional study outcomes included an analysis of key hospital resources usage such as oxygen, length of stay (LOS) and requirement for intensive or high dependency care. The majority of data to date were collected from patients admitted to hospital during the early community waves, although further data collection and analyses are planned. Here, we present a descriptive review of patients hospitalised with COVID-19 in New Zealand from 26 February to 5 October 2020, encompassing from the first reported case in New Zealand until the end of the second wave of community transmission.

Methods

We conducted a multi-centre retrospective cohort study. Eleven DHBs across New Zealand were enrolled including Auckland, Bay of Plenty, Canterbury, Capital and Coast, Counties Manukau, Hutt Valley, Lakes, MidCentral, Southern, Waikato and Waitematā. Patients of any age admitted to participating DHBs with a primary clinical diagnosis of COVID-19, based on contemporaneous Ministry of Health definitions,[[11]] were identified by site investigators and included for analysis. We enrolled both confirmed COVID-19 cases, i.e., those with symptomatology and positive SARS-CoV-2 polymerase chain reaction (PCR) testing and probable cases. Probable cases were defined as a symptomatic close contact of a confirmed case (epi-link), or a case that met the clinical criteria, in whom other aetiologies explaining the clinical presentation had been excluded, and where laboratory testing was either suggestive of SARS-CoV-2 or inconclusive. Patients with COVID-19 hospitalised for less than six hours or admitted primarily for an unrelated diagnosis were excluded.

Data were extracted from individual patient records by investigators. Patients identifying as more than one ethnic group were analysed as a single ethnicity, prioritised in the order of Māori, Pasifika, Asian then NZ European/Other.[[3]] A returned traveller was defined as having travelled internationally within the 14 days preceding symptom onset. Presenting symptoms related to self-reported symptomatology during or prior to hospital admission. Blood and biochemical results were obtained from the first laboratory tests taken during admission. LOS was calculated from the date of admission to the date of hospital discharge or death and included time spent in inpatient rehabilitation facilities. Inpatient mortality was defined as death during hospital admission. The presence or absence of some patient characteristics were variably documented in the clinical notes. Therefore, data are reported as the number of patients with a characteristic, over the denominator of patients for whom this information was available.  

De-identified data were collected by investigators and uploaded to a secure online database. Descriptive analyses were performed using pooled data. We performed bivariate logistic regression of a composite “severe outcome”, defined as admission to intensive/high dependency care (ICU/HDU) or inpatient death, against patient age, ethnicity and selected co-morbidities. Statistical analysis was performed in Stata 16.0 (StataCorp, College Station, TX, United States). Ethical approval for this study was obtained from the New Zealand Health and Disability Ethics Committee (reference: 20/NTB/72/AM02) and local approvals were obtained at each participating site.

Results

Eighty-four patients were identified from the 26 February to 5 October 2020 with data submitted from eight of the eleven participating district health boards (DHBs). The majority were hospitalised in three Auckland DHBs, Auckland, Counties-Manukau and Waitemata (n=56, 67%) (Figure 1). Nine patients (11%) were healthcare workers and four (5%) were pregnant. Seventeen patients (20%) were returned travellers. A positive SARS-CoV-2 test was collected from 66/76 (87%) patients during admission. The remainder had either a positive community test prior to admission or fulfilled the ‘probable’ case criteria.

Figure 1: Proportion of patients admitted with COVID-19, by District Health Board, 2020.

Demographics and Co-morbidities

Forty-one patients (49%) were men, and the median age was 58 years [n=83, interquartile range [IQR] 41.7–70.3 years]. The most common age decile was 50–59 years (19/83, 23%) (Table 1). Sixteen patients (19%) were under 40 years. The only child in the cohort (≤18 years old) was a 2-month-old infant. By ethnicity, 38 (45%) patients identified as NZ European; 19 (23%) Pasifika; 13 (15%) as Māori; 12 (14%) as Asian and 2 (2%) as Other (Table 2). Māori were the youngest group admitted, with a median age of 45 years [IQR: 42–58 years]. NZ European/Other were the oldest, median age 63 years [IQR: 51–78 years]. Forty-eight (57%) patients had at least one reported pre-existing co-morbidity. Metabolic co-morbidities included chronic cardiac disease (12/82, 15%), hypertension (26/82, 32%), diabetes (18/81, 22%) and obesity (16/66, 24%) (Table 1). Twenty-five (32%) of 79 patients were ex-smokers and 2 (3%) were current smokers.

A record of a composite severe outcome was available in 83/84 patients, with 19/83 (23%) dying or admitted to ICU/HDU. When correlated against a severe outcome of death or ICU/HDU admission, none of age, ethnicity or co-morbidities were shown to confer a worse outcome (Table 1). Māori had the highest proportion admitted to ICU/HDU (38%) (Table 2). Those identified as NZ European/Other had the highest in-hospital mortality (21%) but were also the oldest (mean=64 years [IQR: 51–80 years]) with the lowest rate of ICU/HDU admission (8%). When adjusted for age, the adjusted odds ratio (aOR) of a composite severe outcome for Māori was 3.7 (95% Confidence Interval (CI): 0.93–14.7, p=0.06) when compared to Non-Māori/Non-Pasifika. For Pasifika the aOR was 0.58 (95% CI: 0.14–2.29, p=0.44).

View Tables 1 & 2.

Clinical features

Patients reported a median of seven days of symptoms [IQR: 4–10 days] prior to presentation. The most common were cough (66/83, 80%) and shortness of breath (58/84, 69%). Systemic symptoms including fever (56/84, 67%), myalgia (28/66, 42%) and fatigue (48/75, 64%) were frequently described. Gastrointestinal symptoms including abdominal pain (9/73, 12%), nausea or vomiting (12/72, 17%) and diarrhoea (12/71, 17%) were also reported. On admission, 23/71 (32%) had a temperature ≥38°C. The median heart rate (90 beats per minute [IQR: 78–101bpm]), respiratory rate (20 respirations per minute [IQR: 18–25resps/min]) and oxygen saturations (96% [IQR: 94–98%]) on arrival were generally within normal ranges (Table 3). Oxygen saturations ≤92% were recorded in 10/81 (12%) patients on admission. View Table 3.

Median measurements of blood count parameters at admission, including liver function tests and electrolytes, were predominately in normal ranges although median lactate dehydrogenase (LDH) (360U/L [IQR: 313–471U/L]), C-reactive protein (41mg/L [IQR: 8–96mg/L]), D-dimer (670ng/mL [IQR: 300–950ng/mL]) and ferritin (925ug/L [IQR: 304–1394ug/L]) were noted as being elevated (Table 3). Admission chest x-rays showed infiltrates in 46/76 (61%) patients.

More than half of patients (46/83, 55%) hospitalised with COVID-19 experienced a complication of their illness (Table 4). A cardiac arrhythmia was documented in 6/80 patients (8%); 6/82 patients (7%) developed bacteraemia, 3/83 patients (4%) had bleeding complications, and 1/83 (1%) had a pulmonary embolus. Regarding therapeutics, 18/82 (22%) patients received oral or intravenous (IV) corticosteroids during admission, 48/82 (59%) received an antibiotic and 2/83 (2%) an antiviral (1 entecavir, 1 unknown). During hospital admission, 42/82 patients (51%) required oxygen with 18/82 (22%) requiring high-flow (≥5L/min). The median duration of oxygen usage was five days [IQR: 2–9 days].

View Table 4.

Outcomes

The median length of hospital stay (LOS) was four days [IQR: 2–15 days]. The mean LOS was nine days [standard deviation=11 days]. Nineteen patients (19/82, 23%) were admitted for more than 14 days (Figure 2). Twelve patients (12/83, 14%) were admitted to ICU/HDU. Six (7%) required invasive ventilation for a median duration of 15 days [IQR: 13–15 days]. No patients required extracorporeal support. Two (2%) underwent haemodialysis. The median duration of ICU/HDU admission was 10 days [IQR: 2–15 days].

In-hospital death occurred in 10 patients (10/83, 12%). The median age at death was 82.9 years [IQR: 72.8–94.4 years] and the median admission length prior to death was 14 days [IQR: 7–21 days]. Seven (70%) of these deaths occurred in patients not admitted to ICU/HDU.

Figure 2: Length of stay of patients hospitalised with COVID-19 February to October, 2020

Discussion

Here we present early data from the COHESION study: a retrospective, multi-centre study reviewing the demographics and outcomes of patients hospitalised with COVID-19 in New Zealand from the early waves of the pandemic. Despite a comparatively low population prevalence of COVID-19, hospitalised patients still required significant healthcare resourcing with high rates of oxygen use, prolonged admissions and multiple inpatient complications. In-hospital mortality was considerable. Deceased patients were elderly and most died without admission to ICU/HDU; however, severe outcomes occurred across the age spectrum.

During the time period studied, 1866 COVID-19 cases (38 per 100,000 population) and around 120 hospitalisations were reported in New Zealand.[[10]] Therefore, our study captured 70% of those admitted with COVID-19 and can be considered a good representation of hospitalisations nationally. Similar to international findings, many hospitalised patients were elderly;[[4, 12]] however, the median age of our cohort was younger than comparable studies.[[12]] This may reflect many of New Zealand’s early COVID-19 cases occurring as imported infections in returned travellers who tended to be younger, predominately European and of high socioeconomic status.[[1, 13]] Co-morbidities were common among those hospitalised. Although we did not collect data on the effect of COVID-19 on control of co-morbidities such as diabetes, our study emphasises the complex healthcare needs of COVID-19 patients that extend beyond direct effects of the virus.

Patients hospitalised with COVID-19 in New Zealand experienced a high prevalence of complications, notably acute kidney injury, delirium and cardiac arrhythmia. There was a discrepancy between the prescription of antibacterial medication and the prevalence of bacteraemia. While bacteraemia is present in only a minority of bacterial infections that require treatment, current literature suggests that super-added bacterial infection with COVID-19 is probably less common than in other viral pandemics.[[14]] Due to the importance of antimicrobial stewardship in combatting bacterial antimicrobial resistance, ongoing work to identify which patients with COVID-19 also have bacterial superinfection is critical.

The proportion of patients who died in our study was approximately half that reported in the United Kingdom (26%),[[4]] but comparable to a large multi-centre study in the USA (14% with a further 3% discharged to hospice).[[15]] Of note, both these and our study were conducted prior to vaccination and the widespread usage of dexamethasone, remdesivir and tocilizumab, repurposed agents which have been shown to improve outcomes in hospitalised patients with COVID-19. Only small numbers in our cohort received anti-viral agents, immune modulators or corticosteroids, in keeping with international practice at the time. It is notable that only a minority of patients who died during hospital admission received ICU/HDU treatment suggesting either that they died rapidly, or would not have benefited from more invasive interventions offered by ICU/HDU such as ventilation, inotrope support or renal replacement therapy. The older age of this cohort, and duration of hospital stay prior to death appears to suggest the latter. An important implication of this finding is that planning and resources are needed to provide palliative care for patients dying of COVID-19.

Despite low case numbers in the early waves of the pandemic, COVID-19 hospitalisations absorbed substantial healthcare resources with healthcare workers being a high proportion of those hospitalised. There was significant variability between individual patient’s lengths of hospital stay, with prolonged admissions in a substantial minority. This is comparable to the international literature[[16]] and highlights the importance of structures to support holistic care for those with long hospital stays. The proportion of patients admitted to ICU/HDU (14%) was similar to that reported from the UK (17%),[[4]] with many requiring invasive ventilation and resource-intensive proning. The ICU bed capacity of New Zealand is 4.6/100,000 people, lower than comparable healthcare systems,[[17]] with further addition of bed capacity likely limited by the availability of trained nursing staff.[[18]] If a similar proportion of hospitalised cases require ICU admission in future waves of the pandemic, there is a risk the ICU capacity of New Zealand would be exceeded. Strategies to mitigate this could include increasing ICU staffing and bed capacity, and optimising community and ward-based care.

This analysis has not identified any risk factors for death or ICU/HDU admission among those admitted to hospital but are compatible with international studies identifying age as the most important risk factor.[[4]] The small sample size of our study means it is underpowered to detect all but the largest risk factors. Although we did not identify Māori or Pasifika ethnicity as being associated with an increased risk of death or ICU/HDU admission in our analysis, this remains an important association to monitor. We used a prioritised ethnic system, assigning a single ethnicity for the purpose of analysis. It is therefore possible that the impact on certain groups, particularly Pasifika, may have been underestimated. Previous work by Steyn et al over a time period similar to our study, identified Māori and Pasifika with COVID-19 were at 2.5–3 times the risk of hospitalisation when compared to NZ European/Other ethnic groups.[[10]] The authors also noted a younger age at admission and longer lengths of hospital stay in Māori and Pasifika, which is consistent with our findings.

Our study does have limitations that influence interpretation. As a retrospective study, complete data could not be obtained for all patients. Data collection was concentrated in tertiary urban centres and caution should be used when generalising to smaller or rural hospitals. The study was not adequately powered to assess risk factors for severe outcomes, however the absence of statistically significant risk associated with ethnicity, age or co-morbidities does not preclude an important relationship. Data collection is ongoing and we hope this will be addressed in future analyses. Finally, since the study end date, there has been considerable progression of knowledge regarding transmission, treatment and progression of COVID-19, as well as emergent viral strains and the development of effective vaccines. Whilst these factors will inevitably alter the demographics and outcomes of those affected, we have identified signals for ongoing research. Further data collection for COHESION will be able to utilise our findings to develop a comparison of the demographics and clinical progression of those affected in early and later outbreaks.

Conclusion

This observational study describes the demographics, clinical course and outcomes of patients hospitalised with COVID-19 in New Zealand during 2020. There was a high proportion of patients who died, particularly while receiving ward-based care, as well as substantial utilisation of ward beds, ICU/HDU beds and oxygen. Our study highlights the high prevalence of co-morbidities that increase complexity of care, and diversity of age and ethnicity. This emphasises not only the need for care which is person- and- whānau-centred and culturally safe during hospitalisation, but also in the community. Whilst further work is required to identify local patient risk factors for progression to severe COVID-19, our preliminary data identify areas of priority for healthcare resourcing to optimise resilience of the New Zealand healthcare system in preparation for endemic COVID-19.

Summary

Abstract

Aim

As New Zealand transitions towards endemic SARS-CoV-2, understanding patient factors predicting severity, as well as hospital resourcing requirements will be essential for future planning.

Method

We retrospectively enrolled patients hospitalised with COVID-19 from 26 February to 5 October 2020 as part of the COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION). Data on demographics, clinical course and outcomes were collected and analysed as a descriptive case series.

Results

Eighty-four patients were identified across eight district health boards. Forty-one (49%) were male. The median age was 58 years [IQR: 41.7–70.3 years]. By ethnicity, hospitalisations included 38 NZ European (45%), 19 Pasifika (23%), 13 Māori (15%), 12 Asian (14%) and 2 Other (2%). Pre-existing co-morbidities included hypertension (26/82, 32%), obesity (16/66, 24%) and diabetes (18/81, 22%). The median length of stay was four days [IQR: 2–15 days]. Twelve patients (12/83, 14%) were admitted to an intensive care unit or high dependency unit (ICU/HDU). Ten (10/83, 12%) patients died in hospital of whom seven (70%) were not admitted to ICU/HDU; the median age at death was 83 years.

Conclusion

Despite initially low case numbers in New Zealand during 2020, hospitalisation with COVID-19 was associated with a high mortality and hospital resource requirements.

Author Information

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. Lydia Foley: Department of Medicine, University of Otago, Christchurch, New Zealand. Juliette Phillipson: Department of Medicine, University of Otago, Christchurch, New Zealand. Sandy Slow: Department of Medicine, University of Otago, Christchurch, New Zealand. Malina Storer: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Jonathan Williman: Department of Population Health, University of Otago, Christchurch, New Zealand. Richard Beasley: Medical Research Institute of New Zealand, Wellington, New Zealand. Hasan Bhally: Infectious Diseases Department, Waitematā District Health Board, Auckland, New Zealand. Cat L Chang: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Jack Dummer: Department of Medicine, University of Otago, Dunedin, New Zealand; Respiratory Medicine Department, Southern District Health Board, Dunedin, New Zealand. Michael Epton: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Mary Furniss: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Kathryn Gracie: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Robert J Hancox: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Thomas Hills: Medical Research Institute of New Zealand, Wellington, New Zealand; Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Stephen Hogg: Infectious Diseases Department, Hutt Valley District Health Board, Hutt Valley, New Zealand. Sandra Hotu: Respiratory Medicine Department, Auckland District Health Board, Auckland, New Zealand. Nethmi Kearns: Medical Research Institute of New Zealand, Wellington, New Zealand. Susan Morpeth: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. David Murdoch: Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand. Nigel Raymond: Infectious Diseases Department, Capital and Coast District Health Board, Wellington, New Zealand. Stephen Ritchie: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Conroy Wong: Respiratory Medicine Department, Counties Manukau-District Health Board, Auckland, New Zealand. Michael J Maze: Department of Medicine, University of Otago, Christchurch, New Zealand; Respiratory Medicine Department, Canterbury District Health Board, New Zealand.

Acknowledgements

Correspondence

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand.

Correspondence Email

aliya.bryce@doctors.org.uk

Competing Interests

Nil.

1) Jefferies S, French N, Gilkison C, et al. COVID-19 in New Zealand and the impact of the national response: a descriptive epidemiological study. Lancet Public Health. 2020 Nov;5(11):e612-e623.

2) Baker MG, Wilson N, Anglemyer A. Successful elimination of Covid-19 transmission in New Zealand. N Engl J Med. 2020 Aug 20;383(8):e56.

3) New Zealand Ministry of Health [Website]. COVID-19: Case demographics. Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-data-and-statistics/covid-19-case-demographics.

4) Docherty AB, Harrison EM, Green CA, et al; ISARIC4C investigators. Features of 20 133 UK patients in hospital with COVID-19 using the ISARIC WHO Clinical Characterisation Protocol: prospective observational cohort study. BMJ. 2020 May 22;369:m1985.

5) Environmental Health Intelligence New Zealand [Website]. Population vulnerability. Available from: https://www.ehinz.ac.nz/indicators/population-vulnerability/

6) Janes R. Rural hospitals in New Zealand. N Z Med J. 1999 Aug 13;112(1093):297-9.

7) Mathur R, Rentsch CT, Morton CE, et al; OpenSAFELY Collaborative. Ethnic differences in SARS-CoV-2 infection and COVID-19-related hospitalisation, intensive care unit admission, and death in 17 million adults in England: an observational cohort study using the OpenSAFELY platform. Lancet. 2021 May 8;397(10286):1711-1724.

8) Tai DBG, Shah A, Doubeni CA, et al. The disproportionate impact of COVID-19 on racial and ethnic minorities in the United States. Clin Infect Dis. 2021 Feb 16;72(4):703-706.

9) Baker M, Barnard LT, Shang J, et al. Close-contact infectious diseases in New Zealand: trends and ethnic inequalities in hospitalisations, 1989 to 2008. A report prepared for the Māori Health Directorate, Ministry of Health. Wellington: University of Otago, 2010. Available from: www.healthyhousing.org.nz.

10) Steyn N, Binny RN, Hannah K, et al. Māori and Pacific people in New Zealand have a higher risk of hospitalisation for COVID-19. N Z Med J. 2021 Jul 9;134(1538):28-43.

11) New Zealand Ministry of Health [Website]. Case definition and clinical testing guidelines for COVID-19. Available from: https://www.health.govt.nz/our-work/diseases-and-conditions/covid-19-novel-coronavirus/covid-19-information-health-professionals/case-definition-and-clinical-testing-guidelines-covid-19.

12) Kim L, Garg S, O'Halloran A, et al. Risk Factors for intensive care unit admission and in-hospital mortality among hospitalized adults identified through the US Coronavirus Disease 2019 (COVID-19)-Associated Hospitalization Surveillance Network (COVID-NET). Clin Infect Dis. 2021 May 4;72(9): e206-e214.

13) Kearns N, Eathorne A, Luff T, et al. Clinical and epidemiological characteristics of COVID-19 in Wellington, New Zealand: a retrospective, observational study. N Z Med J. 2021 Sep 17;134(1542):38-49.

14) Garcia-Vidal C, Sanjuan G, Moreno-García E, et al. Incidence of co-infections and superinfections in hospitalized patients with COVID-19: a retrospective cohort study. Clin Microbiol Infect. 2021 Jan;27(1):83-88.

15) Nguyen NT, Chinn J, Nahmias J, et al. Outcomes and Mortality Among Adults Hospitalized With COVID-19 at US Medical Centers. JAMA Netw Open. 2021 Mar 1;4(3):e210417.

16) Rees EM, Nightingale ES, Jafari Y, et al. COVID-19 length of hospital stay: a systematic review and data synthesis. BMC Med. 2020 Sep 3;18(1):270.

17) Betteridge T, Henderson S. Intensive care in New Zealand: time for a national network. N Z Med J. 2020 Aug 21;133(1520):148-149.

18) Young PJ, Psirides A, Streat S. New Zealand's staffed ICU bed capacity and COVID-19 surge capacity. N Z Med J. 2021 Nov 12;134(1545):8-10.

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On 28 February 2020, Aotearoa New Zealand recorded its first case of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, causing coronavirus disease 2019 (COVID-19) in a traveller returned from the Middle East. A rapid and sustained public health response ensued, including contact tracing, countrywide lockdown and government-managed quarantine of international travellers.[[1,2]] New Zealand successfully eliminated community COVID-19 transmission by May 2020, diverging from most other OECD countries and resulting in both low case numbers and fatalities.[[1]] Further community outbreaks occurred August to September 2020 and in February 2021, again with successful elimination. However, in August 2021, the increased transmissibility of the COVID-19 Delta variant resulted in total case notifications rising across the Auckland region, despite high vaccination rates.[[3]] With relaxation of public health measures, including travel restrictions, it is likely SARS-CoV-2 will eventually become endemic across New Zealand. Understanding patient characteristics, outcomes and resourcing during the early waves may help plan for future outbreaks and this transition to endemic disease.

Whilst knowledge regarding patient risk factors, clinical progression and treatments for COVID-19 in hospitalised patients has progressed rapidly from international large-scale studies,[[4]] there is a paucity of local data. Healthcare in New Zealand is predominately public-funded and is currently delivered by twenty district health boards (DHBs). Sixteen percent of the population live rurally[[5]] and 10% are served by rural hospitals[[6]] which may have limited staffing and resourcing. New Zealand has a diverse ethnic make-up with its population identifying as NZ European (70.2%), Māori (Indigenous peoples) (16.5%), Asian (15.1%), Pasifika (8.1%) and Middle Eastern, Latin American and African (MELAA) (1.5%).[[5]] Global data have indicated disproportionate mortality amongst ethnic minority groups with COVID-19[[7, 8]] and it is recognised that Māori and Pasifika are more likely to contract, and be hospitalised, with infectious diseases[[9]] including COVID-19.[[10]]

To characterise local factors associated with adverse outcomes in hospitalised COVID-19 patients in New Zealand, the multi-centre COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION) study was established in April 2020. Additional study outcomes included an analysis of key hospital resources usage such as oxygen, length of stay (LOS) and requirement for intensive or high dependency care. The majority of data to date were collected from patients admitted to hospital during the early community waves, although further data collection and analyses are planned. Here, we present a descriptive review of patients hospitalised with COVID-19 in New Zealand from 26 February to 5 October 2020, encompassing from the first reported case in New Zealand until the end of the second wave of community transmission.

Methods

We conducted a multi-centre retrospective cohort study. Eleven DHBs across New Zealand were enrolled including Auckland, Bay of Plenty, Canterbury, Capital and Coast, Counties Manukau, Hutt Valley, Lakes, MidCentral, Southern, Waikato and Waitematā. Patients of any age admitted to participating DHBs with a primary clinical diagnosis of COVID-19, based on contemporaneous Ministry of Health definitions,[[11]] were identified by site investigators and included for analysis. We enrolled both confirmed COVID-19 cases, i.e., those with symptomatology and positive SARS-CoV-2 polymerase chain reaction (PCR) testing and probable cases. Probable cases were defined as a symptomatic close contact of a confirmed case (epi-link), or a case that met the clinical criteria, in whom other aetiologies explaining the clinical presentation had been excluded, and where laboratory testing was either suggestive of SARS-CoV-2 or inconclusive. Patients with COVID-19 hospitalised for less than six hours or admitted primarily for an unrelated diagnosis were excluded.

Data were extracted from individual patient records by investigators. Patients identifying as more than one ethnic group were analysed as a single ethnicity, prioritised in the order of Māori, Pasifika, Asian then NZ European/Other.[[3]] A returned traveller was defined as having travelled internationally within the 14 days preceding symptom onset. Presenting symptoms related to self-reported symptomatology during or prior to hospital admission. Blood and biochemical results were obtained from the first laboratory tests taken during admission. LOS was calculated from the date of admission to the date of hospital discharge or death and included time spent in inpatient rehabilitation facilities. Inpatient mortality was defined as death during hospital admission. The presence or absence of some patient characteristics were variably documented in the clinical notes. Therefore, data are reported as the number of patients with a characteristic, over the denominator of patients for whom this information was available.  

De-identified data were collected by investigators and uploaded to a secure online database. Descriptive analyses were performed using pooled data. We performed bivariate logistic regression of a composite “severe outcome”, defined as admission to intensive/high dependency care (ICU/HDU) or inpatient death, against patient age, ethnicity and selected co-morbidities. Statistical analysis was performed in Stata 16.0 (StataCorp, College Station, TX, United States). Ethical approval for this study was obtained from the New Zealand Health and Disability Ethics Committee (reference: 20/NTB/72/AM02) and local approvals were obtained at each participating site.

Results

Eighty-four patients were identified from the 26 February to 5 October 2020 with data submitted from eight of the eleven participating district health boards (DHBs). The majority were hospitalised in three Auckland DHBs, Auckland, Counties-Manukau and Waitemata (n=56, 67%) (Figure 1). Nine patients (11%) were healthcare workers and four (5%) were pregnant. Seventeen patients (20%) were returned travellers. A positive SARS-CoV-2 test was collected from 66/76 (87%) patients during admission. The remainder had either a positive community test prior to admission or fulfilled the ‘probable’ case criteria.

Figure 1: Proportion of patients admitted with COVID-19, by District Health Board, 2020.

Demographics and Co-morbidities

Forty-one patients (49%) were men, and the median age was 58 years [n=83, interquartile range [IQR] 41.7–70.3 years]. The most common age decile was 50–59 years (19/83, 23%) (Table 1). Sixteen patients (19%) were under 40 years. The only child in the cohort (≤18 years old) was a 2-month-old infant. By ethnicity, 38 (45%) patients identified as NZ European; 19 (23%) Pasifika; 13 (15%) as Māori; 12 (14%) as Asian and 2 (2%) as Other (Table 2). Māori were the youngest group admitted, with a median age of 45 years [IQR: 42–58 years]. NZ European/Other were the oldest, median age 63 years [IQR: 51–78 years]. Forty-eight (57%) patients had at least one reported pre-existing co-morbidity. Metabolic co-morbidities included chronic cardiac disease (12/82, 15%), hypertension (26/82, 32%), diabetes (18/81, 22%) and obesity (16/66, 24%) (Table 1). Twenty-five (32%) of 79 patients were ex-smokers and 2 (3%) were current smokers.

A record of a composite severe outcome was available in 83/84 patients, with 19/83 (23%) dying or admitted to ICU/HDU. When correlated against a severe outcome of death or ICU/HDU admission, none of age, ethnicity or co-morbidities were shown to confer a worse outcome (Table 1). Māori had the highest proportion admitted to ICU/HDU (38%) (Table 2). Those identified as NZ European/Other had the highest in-hospital mortality (21%) but were also the oldest (mean=64 years [IQR: 51–80 years]) with the lowest rate of ICU/HDU admission (8%). When adjusted for age, the adjusted odds ratio (aOR) of a composite severe outcome for Māori was 3.7 (95% Confidence Interval (CI): 0.93–14.7, p=0.06) when compared to Non-Māori/Non-Pasifika. For Pasifika the aOR was 0.58 (95% CI: 0.14–2.29, p=0.44).

View Tables 1 & 2.

Clinical features

Patients reported a median of seven days of symptoms [IQR: 4–10 days] prior to presentation. The most common were cough (66/83, 80%) and shortness of breath (58/84, 69%). Systemic symptoms including fever (56/84, 67%), myalgia (28/66, 42%) and fatigue (48/75, 64%) were frequently described. Gastrointestinal symptoms including abdominal pain (9/73, 12%), nausea or vomiting (12/72, 17%) and diarrhoea (12/71, 17%) were also reported. On admission, 23/71 (32%) had a temperature ≥38°C. The median heart rate (90 beats per minute [IQR: 78–101bpm]), respiratory rate (20 respirations per minute [IQR: 18–25resps/min]) and oxygen saturations (96% [IQR: 94–98%]) on arrival were generally within normal ranges (Table 3). Oxygen saturations ≤92% were recorded in 10/81 (12%) patients on admission. View Table 3.

Median measurements of blood count parameters at admission, including liver function tests and electrolytes, were predominately in normal ranges although median lactate dehydrogenase (LDH) (360U/L [IQR: 313–471U/L]), C-reactive protein (41mg/L [IQR: 8–96mg/L]), D-dimer (670ng/mL [IQR: 300–950ng/mL]) and ferritin (925ug/L [IQR: 304–1394ug/L]) were noted as being elevated (Table 3). Admission chest x-rays showed infiltrates in 46/76 (61%) patients.

More than half of patients (46/83, 55%) hospitalised with COVID-19 experienced a complication of their illness (Table 4). A cardiac arrhythmia was documented in 6/80 patients (8%); 6/82 patients (7%) developed bacteraemia, 3/83 patients (4%) had bleeding complications, and 1/83 (1%) had a pulmonary embolus. Regarding therapeutics, 18/82 (22%) patients received oral or intravenous (IV) corticosteroids during admission, 48/82 (59%) received an antibiotic and 2/83 (2%) an antiviral (1 entecavir, 1 unknown). During hospital admission, 42/82 patients (51%) required oxygen with 18/82 (22%) requiring high-flow (≥5L/min). The median duration of oxygen usage was five days [IQR: 2–9 days].

View Table 4.

Outcomes

The median length of hospital stay (LOS) was four days [IQR: 2–15 days]. The mean LOS was nine days [standard deviation=11 days]. Nineteen patients (19/82, 23%) were admitted for more than 14 days (Figure 2). Twelve patients (12/83, 14%) were admitted to ICU/HDU. Six (7%) required invasive ventilation for a median duration of 15 days [IQR: 13–15 days]. No patients required extracorporeal support. Two (2%) underwent haemodialysis. The median duration of ICU/HDU admission was 10 days [IQR: 2–15 days].

In-hospital death occurred in 10 patients (10/83, 12%). The median age at death was 82.9 years [IQR: 72.8–94.4 years] and the median admission length prior to death was 14 days [IQR: 7–21 days]. Seven (70%) of these deaths occurred in patients not admitted to ICU/HDU.

Figure 2: Length of stay of patients hospitalised with COVID-19 February to October, 2020

Discussion

Here we present early data from the COHESION study: a retrospective, multi-centre study reviewing the demographics and outcomes of patients hospitalised with COVID-19 in New Zealand from the early waves of the pandemic. Despite a comparatively low population prevalence of COVID-19, hospitalised patients still required significant healthcare resourcing with high rates of oxygen use, prolonged admissions and multiple inpatient complications. In-hospital mortality was considerable. Deceased patients were elderly and most died without admission to ICU/HDU; however, severe outcomes occurred across the age spectrum.

During the time period studied, 1866 COVID-19 cases (38 per 100,000 population) and around 120 hospitalisations were reported in New Zealand.[[10]] Therefore, our study captured 70% of those admitted with COVID-19 and can be considered a good representation of hospitalisations nationally. Similar to international findings, many hospitalised patients were elderly;[[4, 12]] however, the median age of our cohort was younger than comparable studies.[[12]] This may reflect many of New Zealand’s early COVID-19 cases occurring as imported infections in returned travellers who tended to be younger, predominately European and of high socioeconomic status.[[1, 13]] Co-morbidities were common among those hospitalised. Although we did not collect data on the effect of COVID-19 on control of co-morbidities such as diabetes, our study emphasises the complex healthcare needs of COVID-19 patients that extend beyond direct effects of the virus.

Patients hospitalised with COVID-19 in New Zealand experienced a high prevalence of complications, notably acute kidney injury, delirium and cardiac arrhythmia. There was a discrepancy between the prescription of antibacterial medication and the prevalence of bacteraemia. While bacteraemia is present in only a minority of bacterial infections that require treatment, current literature suggests that super-added bacterial infection with COVID-19 is probably less common than in other viral pandemics.[[14]] Due to the importance of antimicrobial stewardship in combatting bacterial antimicrobial resistance, ongoing work to identify which patients with COVID-19 also have bacterial superinfection is critical.

The proportion of patients who died in our study was approximately half that reported in the United Kingdom (26%),[[4]] but comparable to a large multi-centre study in the USA (14% with a further 3% discharged to hospice).[[15]] Of note, both these and our study were conducted prior to vaccination and the widespread usage of dexamethasone, remdesivir and tocilizumab, repurposed agents which have been shown to improve outcomes in hospitalised patients with COVID-19. Only small numbers in our cohort received anti-viral agents, immune modulators or corticosteroids, in keeping with international practice at the time. It is notable that only a minority of patients who died during hospital admission received ICU/HDU treatment suggesting either that they died rapidly, or would not have benefited from more invasive interventions offered by ICU/HDU such as ventilation, inotrope support or renal replacement therapy. The older age of this cohort, and duration of hospital stay prior to death appears to suggest the latter. An important implication of this finding is that planning and resources are needed to provide palliative care for patients dying of COVID-19.

Despite low case numbers in the early waves of the pandemic, COVID-19 hospitalisations absorbed substantial healthcare resources with healthcare workers being a high proportion of those hospitalised. There was significant variability between individual patient’s lengths of hospital stay, with prolonged admissions in a substantial minority. This is comparable to the international literature[[16]] and highlights the importance of structures to support holistic care for those with long hospital stays. The proportion of patients admitted to ICU/HDU (14%) was similar to that reported from the UK (17%),[[4]] with many requiring invasive ventilation and resource-intensive proning. The ICU bed capacity of New Zealand is 4.6/100,000 people, lower than comparable healthcare systems,[[17]] with further addition of bed capacity likely limited by the availability of trained nursing staff.[[18]] If a similar proportion of hospitalised cases require ICU admission in future waves of the pandemic, there is a risk the ICU capacity of New Zealand would be exceeded. Strategies to mitigate this could include increasing ICU staffing and bed capacity, and optimising community and ward-based care.

This analysis has not identified any risk factors for death or ICU/HDU admission among those admitted to hospital but are compatible with international studies identifying age as the most important risk factor.[[4]] The small sample size of our study means it is underpowered to detect all but the largest risk factors. Although we did not identify Māori or Pasifika ethnicity as being associated with an increased risk of death or ICU/HDU admission in our analysis, this remains an important association to monitor. We used a prioritised ethnic system, assigning a single ethnicity for the purpose of analysis. It is therefore possible that the impact on certain groups, particularly Pasifika, may have been underestimated. Previous work by Steyn et al over a time period similar to our study, identified Māori and Pasifika with COVID-19 were at 2.5–3 times the risk of hospitalisation when compared to NZ European/Other ethnic groups.[[10]] The authors also noted a younger age at admission and longer lengths of hospital stay in Māori and Pasifika, which is consistent with our findings.

Our study does have limitations that influence interpretation. As a retrospective study, complete data could not be obtained for all patients. Data collection was concentrated in tertiary urban centres and caution should be used when generalising to smaller or rural hospitals. The study was not adequately powered to assess risk factors for severe outcomes, however the absence of statistically significant risk associated with ethnicity, age or co-morbidities does not preclude an important relationship. Data collection is ongoing and we hope this will be addressed in future analyses. Finally, since the study end date, there has been considerable progression of knowledge regarding transmission, treatment and progression of COVID-19, as well as emergent viral strains and the development of effective vaccines. Whilst these factors will inevitably alter the demographics and outcomes of those affected, we have identified signals for ongoing research. Further data collection for COHESION will be able to utilise our findings to develop a comparison of the demographics and clinical progression of those affected in early and later outbreaks.

Conclusion

This observational study describes the demographics, clinical course and outcomes of patients hospitalised with COVID-19 in New Zealand during 2020. There was a high proportion of patients who died, particularly while receiving ward-based care, as well as substantial utilisation of ward beds, ICU/HDU beds and oxygen. Our study highlights the high prevalence of co-morbidities that increase complexity of care, and diversity of age and ethnicity. This emphasises not only the need for care which is person- and- whānau-centred and culturally safe during hospitalisation, but also in the community. Whilst further work is required to identify local patient risk factors for progression to severe COVID-19, our preliminary data identify areas of priority for healthcare resourcing to optimise resilience of the New Zealand healthcare system in preparation for endemic COVID-19.

Summary

Abstract

Aim

As New Zealand transitions towards endemic SARS-CoV-2, understanding patient factors predicting severity, as well as hospital resourcing requirements will be essential for future planning.

Method

We retrospectively enrolled patients hospitalised with COVID-19 from 26 February to 5 October 2020 as part of the COVID-19 HospitalisEd Patient SeverIty Observational Study NZ (COHESION). Data on demographics, clinical course and outcomes were collected and analysed as a descriptive case series.

Results

Eighty-four patients were identified across eight district health boards. Forty-one (49%) were male. The median age was 58 years [IQR: 41.7–70.3 years]. By ethnicity, hospitalisations included 38 NZ European (45%), 19 Pasifika (23%), 13 Māori (15%), 12 Asian (14%) and 2 Other (2%). Pre-existing co-morbidities included hypertension (26/82, 32%), obesity (16/66, 24%) and diabetes (18/81, 22%). The median length of stay was four days [IQR: 2–15 days]. Twelve patients (12/83, 14%) were admitted to an intensive care unit or high dependency unit (ICU/HDU). Ten (10/83, 12%) patients died in hospital of whom seven (70%) were not admitted to ICU/HDU; the median age at death was 83 years.

Conclusion

Despite initially low case numbers in New Zealand during 2020, hospitalisation with COVID-19 was associated with a high mortality and hospital resource requirements.

Author Information

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. Lydia Foley: Department of Medicine, University of Otago, Christchurch, New Zealand. Juliette Phillipson: Department of Medicine, University of Otago, Christchurch, New Zealand. Sandy Slow: Department of Medicine, University of Otago, Christchurch, New Zealand. Malina Storer: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Jonathan Williman: Department of Population Health, University of Otago, Christchurch, New Zealand. Richard Beasley: Medical Research Institute of New Zealand, Wellington, New Zealand. Hasan Bhally: Infectious Diseases Department, Waitematā District Health Board, Auckland, New Zealand. Cat L Chang: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Jack Dummer: Department of Medicine, University of Otago, Dunedin, New Zealand; Respiratory Medicine Department, Southern District Health Board, Dunedin, New Zealand. Michael Epton: Respiratory Medicine Department, Canterbury District Health Board, New Zealand. Mary Furniss: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Kathryn Gracie: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Robert J Hancox: Respiratory Medicine Department, Waikato District Health Board, Hamilton, New Zealand. Thomas Hills: Medical Research Institute of New Zealand, Wellington, New Zealand; Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Stephen Hogg: Infectious Diseases Department, Hutt Valley District Health Board, Hutt Valley, New Zealand. Sandra Hotu: Respiratory Medicine Department, Auckland District Health Board, Auckland, New Zealand. Nethmi Kearns: Medical Research Institute of New Zealand, Wellington, New Zealand. Susan Morpeth: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand. David Murdoch: Department of Pathology and Biomedical Science, University of Otago, Christchurch, New Zealand. Nigel Raymond: Infectious Diseases Department, Capital and Coast District Health Board, Wellington, New Zealand. Stephen Ritchie: Infectious Diseases Department, Auckland District Health Board, Auckland, New Zealand. Conroy Wong: Respiratory Medicine Department, Counties Manukau-District Health Board, Auckland, New Zealand. Michael J Maze: Department of Medicine, University of Otago, Christchurch, New Zealand; Respiratory Medicine Department, Canterbury District Health Board, New Zealand.

Acknowledgements

Correspondence

Aliya Bryce: Microbiology Department, Counties-Manukau District Health Board, Auckland, New Zealand.

Correspondence Email

aliya.bryce@doctors.org.uk

Competing Interests

Nil.

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