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Precision shielding for COVID-19: metrics of assessment and feasibility of deployment
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  • Published on:
    In reply to Pimenta

    Many thanks to Dominic Pimenta for the interesting comment. I respect Pimenta’s well-intentioned activism during the COVID-19 crisis, but here he polarizes the discussion between two schools of thought by using a strawman argument, i.e. that one of the two schools wants to promote high community transmission. Such strawman arguments are prevalent in social media and the blogosphere, but they do not serve scientific discourse for resolution of major questions. I have signed neither the Great Barrington Declaration nor the John Snow Memorandum, so I cannot become an insider apologist for either (1). However, my reading of both documents suggests that neither of them advocates to promote high community transmission. If they do, this is certainly not what I would personally advocate.

    Pimenta draws a correlation from 10 observations on the data that I present on nursing home shielding factors (my Table 3) reaching the conclusion that precision shielding is impossible under high community transmission. This is a precarious exercise with rushed conclusions. These are ecological, whole-country data including only 4 observations with high community transmission. Drawing firm causal inferences from an ecological regression with effective sample size of n=4 is impossible. Sadly, over-confident, stretched causal inferences are common during the COVID-19 crisis. A similar look at the age-stratified data on Table 2 shows that shielding of the elderly was achieved in countries w...

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    Conflict of Interest:
    None declared.
  • Published on:
    A successful demonstration of why 'precision shielding' is impossible with high community transmission
    • Dominic R Pimenta, Research Physician, Chairman Healthcare Workers' Foundation (Reg Charity 1189737)

    The article is predicated on the notion that “The ability to preferentially protect high-risk groups in COVID-19 is hotly debated.” This is a mischaracterisation of the debate. The ability to protect high-risk groups has never been questioned.
    The debate would be better characterised as the ability to focus non-pharmaceutical interventions solely on those most at risk of severe disease due to COVID-19, and removing restrictions and allowing widespread infection amongst the low risk groups. The debate has only ever been between those who advocated only applying NPIs to the highest risk cohorts ("focussed protection") and those that advocate that community wide measures are the only effective means to protect those at highest risk.
    The stated aim of this paper is to demonstrate whether ‘precision shielding’ was achieved in the first wave, and invents a metric to compare incidence and death in the high risk long-term care population vs the low risk younger population. The author uses seroprevalence data from the elderly and the young to estimate infection prevalence, but takes no account of the differing antibody response that would largely confound this approach.
    Using these metrics the author then goes on to ascribe a value judgement as “substantial shielding” or “substantial inverse protection.” Care homes and institutions are already known to be at risk environments for the spread of infectious disease, due to the close contact care work, the m...

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    Conflict of Interest:
    None declared.