Shielding individuals at high risk of COVID-19: a micro-simulation study
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Abstract
Background
One of the proposed interventions for mitigating COVID-19 epidemics, particularly in low-income and crisis-affected settings, is to physically isolate individuals known to be at high risk of severe disease and death due to age or co-morbidities. This intervention, known as ‘shielding’, could be implemented in various ways. If shielded people are grouped together in residences and isolation is imperfect, any introduction of infections within the shielding group could cause substantial mortality and thus negate the intervention’s benefits. We explored the effectiveness of shielding under various modalities of implementation and considered mitigation measures to reduce its possible harms.
Methods
We used an individual-based mathematical model to simulate the evolution of a COVID-19 epidemic in a population of which a fraction above a given age cut-off are relocated to shielding residences, in which they have variable levels of contacts with their original household, the outside world and fellow shielding residents. We set our simulation with the context of an internally displaced persons’ camp in Somaliland, for which we had recently collected data on household demographics and social mixing patterns. We compared an unmitigated epidemic with a shielding intervention accompanied by various measures to reduce the risk of virus introduction and spread within the shielding residences. We did sensitivity analyses to explore parameters such as residence size, reduction in contacts, basic reproduction number, and prior immunity in the population.
Results
Shielded residences are likely to be breached with infection during the outbreak. Nonetheless, shielding can be effective in preventing COVID-19 infections in the shielded population. The effectiveness of shielding is mostly affected by the size of the shielded residence, and by the degree by which contacts between shielded and unshielded individuals are reduced. Reductions in contacts between shielded individuals could further increase the effectiveness of shielding, but is only effective in larger shielded residences. Large shielded residences increase the risk of infection, unless very large reductions in contacts can be achieved. In epidemics with a lower reproduction number, the effectiveness of shielding could be negative effectiveness.
Discussion
Shielding could be an effective method to protect the most at-risk individuals. It should be considered where other measures cannot easily be implemented, but with attention to the epidemiological situation. Shielding should only be implemented through small to medium-sized shielding residences, with appropriate mitigation measures such as reduced contact intensity between shielded individuals and self-isolation of cases to prevent subsequent spread.
Article activity feed
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SciScore for 10.1101/2022.01.03.22268675: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Limitations: There are several limitations to this study. Although we were able to use baseline empirical contact-data, these contact patterns could be further altered if shielding would be implemented and contact dynamics change. We only considered Digaale IDP camp, as to our knowledge it is the only humanitarian setting for which detailed contact and demographic data is available. Social contacts are context specific24, and Digaale is a …
SciScore for 10.1101/2022.01.03.22268675: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
NIH rigor criteria are not applicable to paper type.Table 2: Resources
No key resources detected.
Results from OddPub: Thank you for sharing your code.
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:Limitations: There are several limitations to this study. Although we were able to use baseline empirical contact-data, these contact patterns could be further altered if shielding would be implemented and contact dynamics change. We only considered Digaale IDP camp, as to our knowledge it is the only humanitarian setting for which detailed contact and demographic data is available. Social contacts are context specific24, and Digaale is a relatively small-scale peri-urban settlement, which may not be representative of other low-resource or crisis-affected settings. Our model did not include an additional force of infection from outside the camp, beyond the first seeding event. Fewer than 2% of all contacts were reported to be made outside of the camp in the contact data, so the relative impact of additional transmission from outside the camp in the unshielded population is expected to be small once transmission has already been established. We did not estimate the number of cases and deaths that would be expected after infection, though these are proportional to the number of infections. We focussed our analysis on the impact of shielding high-risk individuals, but only assumed individuals aged 60+ years old to be at high-risk. Although the age-risk profile may well be different in low-resource settings compared to stable settings25, empirical estimates are missing, and similar levels of effectiveness could be expected with broader definitions of high-risk groups. We did not ...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
- Thank you for including a funding statement. Authors are encouraged to include this statement when submitting to a journal.
- No protocol registration statement was detected.
Results from scite Reference Check: We found no unreliable references.
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