Shielding, or self-isolating, those at highest risk from COVID-19 during the first wave of the pandemic may not have been as effective at protecting them from infection and death as hoped, found large UK.
Research led by the University of Glasgow and published in Scientific Reports found that, between March and May 2020, patients advised to shield in NHS Greater Glasgow and Clyde (NHSGGC) experienced higher rates of infection and death than those not advised to shield.
Many western countries, including Scotland, used shielding (extended self-isolation) of people presumed to be at high-risk from COVID-19 to protect them and reduce healthcare demand.
The study looked at data from more than 1.3 million patients registered with GP practices in NHSGGC. Of this group, 27,747 individuals had been advised to shield (self-isolate for extended periods of time), and a further 353,085 individuals had not been advised to shield but were categorised by the researchers as at medium risk of COVID-19 due to health conditions such as diabetes.
The authors found that, compared with low-risk individuals (the remaining 934,239 people in the study), people who had been advised to shield were eight times more likely to have confirmed infections.
Those advised to self-isolate were also five times more likely to die after confirmed infection, while moderate-risk individuals were four times more likely to have confirmed infections than the low-risk group, and five times more likely to die following confirmed infection.
In the shielded group, there were 299 (1.1%) confirmed infections and 140 (0.51%) deaths from COVID-19. In the moderate risk group, there were 1,859 (0.53 %) confirmed infections and 803 (0.23%) deaths; and in the low-risk group, there were 1,190 (0.13% confirmed infections) and 84 (0.01%) deaths from COVID-19.
The study also showed that an age of 70 and over accounted for 49.55% of deaths.
Professor Jill Pell, director of the University of Glasgow's Institute of Health and Wellbeing, said: "Our study highlights that to effectively protect high-risk individuals, shielding should be used alongside other population-wide measures such as physical distancing, face coverings and hand hygiene.
"Our study also showed that shielding may be of limited value in reducing burden on health services because, in spite of the shielding strategy, high risk individuals were at increased risk of death. We believe that, to be effective as a population strategy, shielding criteria would have needed to be widely expanded to include other criteria, such as the elderly."
The study linked GP, prescribing, laboratory, hospital and death records and compared COVID-19 outcomes among shielded and non-shielded individuals in the West of Scotland.
Comparison of COVID-19 outcomes among shielded and non-shielded populations
Bhautesh D. Jani, Frederick K. Ho, David J. Lowe, Jamie P. Traynor, Sean P. MacBride-Stewart, Patrick B. Mark, Frances S. Mair, Jill P. Pel
Published in Nature, 27 July 2021 (Open access)
Many western countries used shielding (extended self-isolation) of people presumed to be at high-risk from COVID-19 to protect them and reduce healthcare demand. To investigate the effectiveness of this strategy, we linked family practitioner, prescribing, laboratory, hospital and death records and compared COVID-19 outcomes among shielded and non-shielded individuals in the West of Scotland. Of the 1.3 million population, 27,747 (2.03%) were advised to shield, and 353,085 (26.85%) were classified a priori as moderate risk.
COVID-19 testing was more common in the shielded (7.01%) and moderate risk (2.03%) groups, than low risk (0.73%). Referent to low-risk, the shielded group had higher confirmed infections (RR 8.45, 95% 7.44–9.59), case-fatality (RR 5.62, 95% CI 4.47–7.07) and population mortality (RR 57.56, 95% 44.06–75.19). The moderate-risk had intermediate confirmed infections (RR 4.11, 95% CI 3.82–4.42) and population mortality (RR 25.41, 95% CI 20.36–31.71) but, due to their higher prevalence, made the largest contribution to deaths (PAF 75.30%).
Age ≥ 70 years accounted for 49.55% of deaths. In conclusion, in spite of the shielding strategy, high risk individuals were at increased risk of death. Furthermore, to be effective as a population strategy, shielding criteria would have needed to be widely expanded to include other criteria, such as the elderly.
Early in the COVID-19 pandemic, a major concern was that the demand on health services would exceed capacity in terms of hospitalisations, intensive care unit (ICU) admissions, and ventilation; hence, policy-makers sought interventions that could flatten the curve in severe cases to avoid hospitals becoming overwhelmed. It was assumed that sub-groups of the population would have worse prognosis and, therefore, contribute disproportionately to adverse outcomes and healthcare demands.
Asian countries could implement case and contact finding. Early, widespread ‘test, trace, isolate’ strategies were made possible by their higher testing capacity and greater willingness to monitor and enforce compliance.
In contrast, Europe and the USA were obliged to rely more heavily on non-pharmaceutical interventions in the first wave of the pandemic; general measures, such as physical distancing, face coverings, hand hygiene and lock-downs, designed to reduce transmission in the population as a whole, supplemented by shielding of those assumed to be at higher risk. Notably, Sweden, an outlier in not applying lock-down, nonetheless mandated shielding.
In the UK, a Vulnerable Patient List was produced comprising two categories labelled high risk, highest risk or clinically extremely vulnerable and moderate risk, at risk or clinically vulnerable by various UK organisations. In this manuscript, they are referred to as shielded and moderate risk respectively, with the remaining population labelled low-risk. The shielded group received individual letters strongly recommending they self-isolate over a protracted period; not leaving their homes and avoiding non-essential contact with household members.
In Scotland, the shielded group was offered support through a number of interventions; for example, 53% signed up to have food support, including home delivery of free food boxes and priority food delivery6. Additional local schemes were set up to provide home delivery of medicines6. Individuals in the shielded group were also eligible to apply for Statutory Sick Pay. In contrast, the moderate risk category was simply advised to be vigilant in adhering to general advice, for example, using hand sanitisers, wearing a face covering, and maintaining 2-m distance when entering indoor public spaces.
The category definitions were based largely on expert opinion informed by our understanding of previous viruses and the need for better definitions has been highlighted and discussed. Studies are emerging of the risk factors associated with COVID-19 outcomes.
Among two million UK community-based app users self-reported heart disease, kidney disease, lung disease, diabetes and obesity were associated with self-reported hospital admission and respiratory support for COVID-199. Similarly, linkage of family practitioner records of 17 million people in England reported a wide range of long-term conditions associated with in-hospital death from COVID-19 including: respiratory, heart, liver and kidney disease, diabetes, cancers, stroke and organ transplantation10. Unfortunately, the investigators did not have access to deaths in the community. COVID-19 risk scores are being developed in an attempt to improve identification of high risk individuals who could be advised to shield11 but attempts to investigate the potential contribution of a shielding strategy to population-level outcomes and healthcare demands have so far been largely limited to mathematical modelling12,13,14,15,16,17,18,19,20.
The aims of this study were to compare those classified, a priori, as high risk (and therefore advised to shield) and those classified as moderate and low-risk, in terms of their actual risk of COVID-19 infection and outcomes and the extent to which they accounted for COVID-19 related outcomes at a population level.
Of the 1,315,071 people registered with family practitioners in NHS Greater Glasgow and Clyde in the West of Scotland, 26,747 (2.03%) were on the shielding list and 353,085 (26.85%) were classified, a priori, as moderate-risk. Of the 26,747 shielded group, 18,147 (55.78%) had severe respiratory disease, 5349 (16.44%) were on immunosuppressive therapies, 2491 (7.66%) had specific cancers, 1245 (3.83%) had received organ transplants, 475 (1.78%) were on renal dialysis, and less than five were pregnant and had severe heart disease.
Of the 353,085 classified as moderate-risk, 160,215 (45.38%) had hypertension, 151,865 (43.01%) had chronic lung disease, 139,568 (39.53%) were ≥ 70 years of age, 64,358 (18.23%) had diabetes, 48,571 (13.81%) had heart disease, and 1195 (0.34%) had a weakened immune system.
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