Precision shielding for COVID-19: metrics of assessment and feasibility of deployment

Abstract

Background. The ability to preferentially protect high-groups in COVID-19 is hotly debated. Here, the aim is to present simple metrics of such precision shielding of people at high-risk of death after infection by SARS-CoV-2; demonstrate how they can estimated; and examine whether precision shielding was successfully achieved in the first COVID-19 wave. Methods. The shielding ratio, S, is defined as the ratio of prevalence of infection among people at a high-risk group versus among people in a low-risk group. The contrasted risk groups examined here are according to age (>=70 versus <70 years), and institutionalized (nursing home) setting. For age-related precision shielding, data were used from large seroprevalence studies with separate prevalence data for elderly versus non-elderly and with at least 1000 assessed people >=70 years old. For setting-related precision shielding, data were analyzed from 10 countries where information was available on numbers of nursing home residents, proportion of nursing home residents among COVID-19 deaths, and overall population infection fatality rate. Findings. Across 17 seroprevalence studies, the shielding ratio S for elderly versus non-elderly varied between 0.4 (substantial shielding) and 1.6 (substantial inverse protection, i.e. low-risk people being protected more than high-risk people). Five studies in USA all yielded S=0.4-0.8, consistent with some shielding being achieved, while two studies in China yielded S=1.5-1.6, consistent with inverse protection. Assuming 25% infection fatality rate among nursing home residents, S values for nursing home residents ranged from 0.07 to 3.1. The best shielding was seen in South Korea (S=0.07) and modest shielding was achieved in Israel, Slovenia, Germany, and Denmark. No shielding was achieved in Hungary and Sweden. In Belgium (S=1.9), UK (S=2.2) and Spain (S=3.1), nursing home residents were far more frequently infected that the rest of the population. Interpretation. The experience from the first wave of COVID-19 suggests that different locations and settings varied markedly in the extent to which they protected high-risk groups. Both effective precision shielding and detrimental inverse protection can happen in real-life circumstances. COVID-19 interventions should seek to achieve maximal precision shielding.

Clinical course and outcomes of critically ill COVID-19 patients in two successive pandemic waves

“…Our findings are in contrast to studies from other countries reporting a lower disease severity and/or mortality in the second wave (13), but the degree of hypoxemia in our patients was among the most severe of those reported worldwide (1,4,7,8,13). Our results confirm that the risk of severe adverse outcomes and death in SARS-CoV-2 infected individuals shows extreme stratification according to age, which may improve understanding of the disease and patient management (14).…”

Assessing mandatory stay‐at‐home and business closure effects on the spread of COVID‐19

“…This further suggests that restrictive measures do not clearly achieve protection of vulnerable populations. Some evidence also suggests 40 that sometimes under more restrictive measures, infections may be more frequent in settings where vulnerable populations reside relative to the general population 40 …”

Reconciling estimates of global spread and infection fatality rates of COVID‐19: An overview of systematic evaluations

“…Differences exist also within a country; for example within the USA, IFR differs markedly in disadvantaged New Orleans districts versus affluent Silicon Valley areas. Differences are driven by population age structure, nursing home populations, effective sheltering of vulnerable people, 74 medical care, use of effective (eg dexamethasone) 75 or detrimental (eg hydroxychloroquine) 76 treatments, host genetics, 77 viral genetics and other factors.…”