Socio-demographic heterogeneity in the prevalence of COVID-19 during lockdown is associated with ethnicity and household size: Results from an observational cohort study

Abstract

Background: Accumulating evidence indicates that COVID-19 causes adverse outcomes in ethnic minority groups. However, little is known about the impact of ethnicity and household size on acquiring infection with SARS-CoV-2. Methods: We undertook a retrospective cohort study, in Leicester (UK), of all individuals assessed for COVID- 19 with polymerase chain reaction (PCR) testing at University Hospitals of Leicester NHS Trust between 1st March and 28th April 2020. We used logistic regression to identify sociodemographic, clinical and temporal factors associated with SARS-CoV-2 PCR positivity before/after lockdown. Findings: 971/4051 (24.0%) patients with suspected COVID-19 were found to be PCR positive for SARS-CoV-2. PCR positivity was more common amongst individuals from ethnic minortiy backgrounds than their White counterparts (White 20.0%, South Asian 37.5%, Black 36.1%, Other 32.2%; p<0.001 for all ethnic minority groups vs White). After adjustment, compared to White ethnicity, South Asian (aOR 2.44 95%CI 2.01, 2.97), Black (aOR 2.56 95%CI 1.71, 3.84) and Other (aOR 2.53 95%CI 1.74, 3.70) ethnicities were more likely to test positive, as were those with a larger estimated household size (aOR 1.06 95%CI 1.02, 1.11). We saw increasing proportions of positive tests in the three weeks post-lockdown amongst the ethnic minority , but not the White, cohort. Estimated household size was associated with PCR positivity after, but not before, lockdown (aOR 1.10 95%CI 1.03, 1.16). Interpretation: In individuals presenting with suspected COVID-19, those from ethnic minority communities and larger households had an increased likelihood of SARS-CoV-2 PCR positivity. Pandemic control measures may have more rapid impact on slowing viral transmission amongst those of White ethnicity compared to ethnic minority groups, Research is urgently required to understand the mechanisms underlying these dis-uncertain but are likely to be multifactorial and driven by a combination of social, cultural, economic and comorbidity factors and are currently subject to a UK governmental inquiry[7]. To date the focus has been on the clinical outcomes of COVID-19 in different ethnic groups. However, emerging evidence seems to suggest that demographic factors including ethnicity may impact upon risk of acquiring infection with SARS-CoV-2 (defined by a positive polymerase chain reaction (PCR) assay for SARS-CoV-2 on nasopharyngeal sampling). A recent UK study has demonstrated male gender, Black ethnicity, urban living and deprivation to be associated with PCR positivity in a primary care setting. However, those from ethnic minority backgrounds comprised less than 10% of the total cohort [8]. A UK Biobank study, which included data on hospital attenders, found that risk of infection was higher in those of Black and South Asian ethnicity and also demonstrated that socioeconomic deprivation and lower educational level may also increase risk [9]. Previous work in China from specialised clinics found conflicting results for age and sex predicting PCR positivity [10] and a recent meta-analysis suggested 56% of PCR positive patients were male [11] but did not present data on ethnicity. These emerging data underpin an urgent need to confirm an association between ethnicity and the probability of SARS-CoV-2 PCR in individuals presenting to hospital for clinical assessment for suspected COVID-19 and to discuss the underlying mechanisms driving such an association. Additionally, little is known about whether the social distancing and lockdown measures, implemented by most governments across the world in response to increases in COVID-19 case numbers, vary in efficacy in different ethnic and socioeconomic groups. Understanding any such association is highly relevant to the design of effective health policies worldwide, as it would have a significant impact on the clinical assessment and management of suspected COVID-19 and allow for targeted public health interventions aimed at specific ethnic minority groups in advance of future pandemic waves. We therefore undertook an observational cohort study of patients admitted to the University Hospitals of Leicester NHS Trust, which provides secondary healthcare to a catchment population of over 1 million people in one of the most ethnically diverse regions of the UK. Our objectives were firstly to investigate the factors associated with prevalent COVID-19 among hospital attenders, and secondly to establish whether temporal changes in the proportion of positive test results before and after institution of lockdown measures differ by ethnicity.