Background
Coronavirus (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) [
1]. It was first detected in Wuhan City, China, in December 2019 during a local outbreak of respiratory illnesses [
1] and by March 2020 the World Health Organisation had declared it a global pandemic [
2]. At the time of writing, Australia had already been exposed to eight different waves of COVID-19 [
3], however the delta-wave outbreak (June 16, 2021 to December 15, 2021) was one of the most fatal, especially for younger populations [
3]. Over eighty thousand COVID-19 cases were recorded in New South Wales (NSW) during this timeframe (mean = 453.4 cases/day), with a case fatality rate of 0.71% [
3]. Although extensive public health measures had already been implemented to reduce case numbers and fatalities at the time of the delta wave outbreak, (e.g. legislation enforcing mask wearing and isolation of cases, and campaigns promoting vaccination uptake) [
1,
2], the highly contagious and evolving nature of the virus meant that case fatality rates still inevitably remained high. Moreover, beyond case-fatalities, there is now a growing body of evidence that COVID-19 has long-term psychological (e.g. anxiety and depression) and physical (e.g. palpitations, sleep difficulty, hair-loss, myalgia, fatigue, anosmia and dizziness) impacts on the quality of life of many of its survivors [
4,
5]. It has also profoundly impacted the health of the general population, particularly health-care workers, due to increased work-related stressors [
6].
People with substance use disorders (SUDs) have higher rates of comorbidities, (such as mental health, diabetes, chronic obstructive pulmonary disease, chronic kidney disease and hepatitis C) [
7,
8], than the general population. Additionally, they often face significant social disadvantages, such as homelessness, poverty, and discrimination, which can be barriers to healthcare service access [
7,
9,
10]. Consequently, not only are they more vulnerable to a more severe COVID-19 illness but they are also less likely to have access to the support, information, and tools to facilitate and/or enable COVID-19 prevention, screening, and treatment [
7,
9]. Emerging data, largely from North America, has illustrated that people with SUDs are significantly more likely to develop [
8,
10‐
13], be hospitalised [
8,
10‐
13] or die [
8,
10‐
13] from COVID-19 than people without SUDs. Indeed, one large retrospective case control study (
n = 73,099,850) conducted in North America in 2020 [
8] found that, of all substance users, those with opioid use disorders (both recent and long-term diagnosis) were the most at risk of COVID-19 acquisition compared to non-substance users (OR = 10.2 (9.1–11.5) and 2.4 (2.2–2.6)) respectively) [
8]. Thus, urgent implementation of public health measures targeting this at-risk group was critical.
South Eastern Sydney Local Health District (SESLHD) Drug and Alcohol Services have provided a range of inpatient and community-based treatment and harm reduction services for people with SUDs for over 60 years [
14]. This includes provision of opioid dependence treatment (ODT) with either oral methadone, sublingual buprenorphine (SL-BPN) or long acting depot buprenorphine (LADB) to between 520 to 600 clients at any one time, as well as counselling and social support [
14]. Prior to COVID-19, ODT had conditions requiring daily attendance for dosing at either clinics or community pharmacies (for methadone and SL-BPN), with limited takeaway doses (TADs) available for clients assessed as ‘low risk’ for safety [
15]. COVID-19 raised significant concerns for ODT services in their ability to implement effective social distancing, personal protective equipment (PPE) and isolation of cases- necessary to protect clients, staff, and their families [
7,
15‐
17]. Additionally, according to some recent international studies, clients with SUDs had (and still have) significantly lower vaccination rates than the rest of their communities [
18‐
23].
In April 2020, in response to the public health emergency, SESLHD dramatically modified its delivery of ODT with the aims of reducing the spread of COVID-19 and maintaining continuity of care [
15,
16] by: increasing use of TADs; transferring clients to local community pharmacies for dosing; encouraging the use of LADB (enabling once a month dosing); increasing the use of telehealth services with clients; introducing perimeter screening of staff and clients entering clinic settings; enforcing the use of PPE for staff and mask wearing for clients in clinical settings; enforcing mandatory COVID-19 vaccination of staff; encouraging and providing COVID-19 vaccination to clients; and ensuring access to reverse transcriptase polymerase chain reaction (PCR) (and later rapid antigen [RAT]) testing for staff and clients [
15,
16]. Other societal changes occurred in Australia outside of the treatment setting, at various periods of the COVID-19 pandemic, including provision of emergency housing for people with unstable accommodation, greater economic assistance for people with reduced employment [
24,
25], restrictions to travel in the community [
26], and free COVID-19 vaccination rollouts via medical practices and pharmacies [
26].
Many evaluations of ODT service changes in response to COVID-19 have demonstrated that neither increasing the number of TADs of methadone or SL-BPN, nor switching clients to LADB treatment was associated with negative treatment outcomes or poorer treatment adherence [
15,
27‐
31]. Additionally, there is evidence that clients who received more TADs or who were on LADB had better continuity of care when in isolation, higher treatment retention, no significant increase in substance use, and a higher satisfaction with treatment and care in general [
15,
31].
However, we believe that this is the first study to evaluate whether these service changes were effective in reducing the spread of COVID-19 amongst ODT clients. This study will focus on the delta COVID-19 wave which commenced in NSW mid-2021 [
32] and specifically the 4-month period August 1st, 2021 to November 30th, 2021. The reason behind the above timeframe is the relatively low total number of COVID-19 cases that had occurred across SESLHD (a population catchment of 1 million people) and the whole of NSW (population of 8.2 million) [
33] prior to August 2021 (
n = 928 and
n = 8,725 respectively) [
34‐
36] compared to the significantly larger number that occurred between August 1st, and November 30th, 2021 (
n = 2,366 and
n = 73,002 respectively) [
34‐
36]. In fact, SESLHD ODT services had record of only one COVID-19 positive case occurring prior to June 2021. Additionally, during the selected timeframe, only PCR tests were considered diagnostic [
37], and all positive PCR tests were automatically recorded centrally in a large database, the NSW Notifiable Conditions Information Management System (NCIMS) [
38]. However, in November 2021, due to the increasing number of positive cases, the Therapeutic Goods Administration began authorising the sale of select self-test rapid antigen test (RAT) kits [
39]. RAT tests were required to have a clinical sensitivity of at least 80% and a clinical specificity of at least 98% [
40,
41] and by January 2022 were considered sufficient for a positive COVID-19 diagnosis in NSW [
37,
42]. This meant accurate capture of all positive cases became increasingly difficult as positive results were not automatically reported to NSW Health.
The primary aim of this study was to determine whether treatment characteristics (dosing site, frequency required to attend clinic/pharmacy for dosing and medication type [methadone, SL-BPN, LADB]) or client characteristics (demographics, housing, employment, and vaccination status) significantly impacted on COVID-19 infection rates in ODT populations. The secondary aim was to identify whether infection rates of SESLHD ODT clients were comparable with the infection rates of NSW at large.
Discussion
SESLHD covers nine local governments areas, expanding from Sydney Central Business District to the Royal National Park, and manages eight public hospitals, twelve community health centres, nine oral health clinics, as well as mental health, youth health, sexual health and imaging and pathology services [
50]. It also offers three major public drug and alcohol clinics located in Surry Hills, Kogarah, and Sutherland [
50].
Although preventative strategies such as reducing the frequency that clients are required to attend clinic/pharmacy for dosing by increasing TADs, transferring clients’ dosing points to pharmacy and encouraging clients to switch to LADB from methadone or SL-BPN have taken place nationally and globally since the outbreak of the pandemic [
15,
27‐
31], this appears to be the first study to determine whether these strategies protected this already vulnerable population against COVID-19 infection.
Our findings demonstrate strong evidence linking employment status, vaccination status, dosing location, and frequency of clinic or pharmacy attendance, to the likelihood of attaining COVID-19 infection amongst a cohort of clients receiving ODT between August 1st, and November 30th, 2021. Clients who were required to attend clinic once a week or less for oral ODT and clients receiving LADB were both significantly less likely to acquire COVID-19 than clients required to attend for dosing six or more times a week. However, we were unable to further stratify clients into those receiving weekly versus monthly LADB due to the low sample size of the former group (n = 3).
Clients who identified as Aboriginal also had a higher risk of COVID-19 infection, (although not statistically significant in the multivariate logistic regression model after adjusting for other covariates). This inequity undoubtedly stems from the history of colonial oppression and the ongoing structural violence, racism, stigma, and intergenerational trauma faced by the Aboriginal community, the resultant mistrust in Australian health-care systems [
51], and the consequential lower vaccination rates, poorer treatment adherence, higher rates of missed doses and higher dosing-site attendance requirements than non-Aboriginal clients. In fact, the subgroups of clients known, from prior research, to be at an inherently greater risk of COVID-19 infection (i.e. unemployed, unvaccinated and Aboriginal people) [
7‐
10] were required, on average, to attend for dosing more frequently than their counterparts, based on risk assessments conducted by their prescribing doctors.
The significantly lower COVID-19 vaccination rates amongst our cohort (68%) vs NSW vaccination rates (83%) at the end of October 2021 [
49] could be partially explained by both the younger age of our cohort (vaccinations targeted the elderly first and the AstraZeneca and Pfizer vaccines had only been implemented in NSW six months prior) [
26] and that almost 20% of SESLHD ODT clients identified as Aboriginal (compared to about 3.4% of the population of NSW) [
52]. This hypothesis is supported by the fact that after stratifying by age and excluding those who identified as Aboriginal, the difference in vaccination rates between the SESLHD Drug and Alcohol ODT community and those of NSW at large [
49] reduced, particularly in the younger age group. As of October 21.
st, 2021, 69% of SESLHD ODT Non-Aboriginal clients aged 16–49 were fully vaccinated compared to 70% of the NSW population aged 16–49; whilst 75% of SESLHD ODT Non-Aboriginal Clients aged 50–69 were fully vaccinated compared to 88% of the NSW population aged 50–69 [
49]
Data on the proportion of Aboriginal people in NSW fully vaccinated by the end of October 2021, stratified by demographics such as age, employment status and gender, is very limited. However, it was reported that by the end of October 2021, 110,371 NSW Aboriginal people had been fully vaccinated [
53], representing about 56% of the NSW Aboriginal population eligible for vaccinations at the time
3 [
52‐
54]. This was slightly less than the proportion of Aboriginal people attending SESLHD for ODT at the time who had been fully vaccinated -approximately 58%. This could perhaps be explained by the fact that Aboriginal people not on ODT may not regularly attend healthcare centres, and thus were less likely to be offered COVID-19 vaccinations on a regular basis.
Whilst international literature had consistently voiced that COVID-19 vaccination rates were lower amongst clients with SUDs, (e.g. in countries such as Italy [
20], America [
21], Canada [
22] and Spain [
23]), our data indicated that vaccination uptake in ODT clients was comparable to the general population after adjusting for age and whether a client identified as Aboriginal. This involved considerable effort and targeted strategies by ODT staff to increase vaccination uptake amongst clients, including providing vaccinations in ODT services, consumer worker activities and financial incentives ($20 supermarket vouchers) for clients to complete vaccination.
Finally, approximately 10% (
n = 41) of SESLHD ODT clients contracted COVID-19 during the timeframe of the study which was over ten times the COVID acquisition rate of NSW adults at large across the same time span (0.8%,
n = 48,558) [
34,
35]. In addition to their requirements to regularly attend clinics/pharmacies for dosing, this also could be explained by their higher rates of unemployment (73% vs 4%) [
55], homelessness (5% vs 0.5%) [
56] and Aboriginality (18% vs 3.4%) [
52], as well as their lower vaccination rates (68% vs 83% as of October 21st, 2021) [
49] and substance use.
This study is relevant as it is the first to quantify the effectiveness, in terms of COVID-19 acquisition, of relaxing requirements for ODT clients to dose at pharmacy and of reducing the frequency of attendance required for supervised dosing. Had these measures not been implemented, our findings suggest that SESLHD ODT clients would likely have suffered significantly higher rates of COVID-19 acquisition with potentially serious complications. However, this study also revealed that clients whose demographics had already placed them at a higher risk of COVID-19 infection (e.g. unemployed, homeless, Aboriginal people) were less likely to have received these treatment adjustments. Much of this inequity can be explained by the structural violence, stigma and/or discrimination faced by these groups resulting in a reluctance to access and trust healthcare services and providers [
51], Although much progress has been made in terms of the prevention (e.g. ongoing vaccine developments and roll-outs) and pharmacological management of COVID-19, it is generally agreed that the COVID-19 pandemic is still far from over [
57]. Thus, further research into how to safely and effectively reduce the frequency of clinic or pharmacy attendance required by this subgroup of clients should remain a priority.
The results of this study are limited as these measures were established across SESLHD ODT clinics at the beginning of the first wave of COVID-19 in NSW (April 2020), prior to any recorded cases occurring amongst SESLHD ODT clients, meaning whilst we were able to conclude that clients who received these interventions were less likely to acquire COVID-19 than those who did not, we could not definitively establish that these interventions themselves caused a reduction in COVID-19 infection rates amongst clients.
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