Herd immunity, COVID-19 and vaccination: some propositions

Author: Srijit Mishra

Title: Herd immunity, COVID-19 and vaccination: some propositions

Abstract: In the herd immunity path to COVID-19, the scientific world has two broad positions. The Great Barrington declaration called for allowing low-risk population to start activities so that other overriding public health concerns beyond COVID-19 and livelihood aspects of the underprivileged are addressed. As against this, the John Snow memorandum suggested continuing with stricter restrictions to save life and open up only when safe or even emergency use vaccination or therapeutic medication is available. The race for vaccines has been in sync with the memorandum with substantive differences in its distribution within and between countries. A critical look into the maths of herd immunity suggests that the goal should be to reach a threshold level and that too through multiple interventions (including alternative care systems), that a substantive independent intervention like vaccine should show efficacy beyond the aggregate threshold level for relative as also absolute risks and that too beyond trials, that recognizing proximate impact can reduce the need for intervention through direct impact to below threshold level, that the proportion of population one needs to reach out for direct intervention will be lower if it is done through public provisioning, and that identifying and prioritizing for groups with greater exposure (or reproduction number) will reduce the overall weighted threshold level and the proportion of people needing direct intervention. Besides, the advantages of natural immunity for those already infected ought to be recognized. Further, an ethical public health posturing also requires to not having an excessive focus on a single disease, to not limiting interventions for a disease to specific types of care, and to not mandating any specific care.

Keywords: COVID-19, Ethical imperative, Great Barrington declaration, Herd immunity, John Snow memorandum, Public health, Public policy, Threshold level, Vaccination.

JEL Code: C69, D63, H49, I18, I31, I38

Weblink: http://www.igidr.ac.in/pdf/publication/WP-2021-024.pdf