Why lockdown? Simplified arithmetic tools for decision-makers, health professionals, journalists and the general public to explore containment options for the novel coronavirus

Gerry Killeen; Samson Kiware

The best-case scenario we could identify for "flattening the curve", as advocated by many national and international authorities, required removing all importation controls to ensure steady reseeding of the epidemic with a small number of cases and relaxing lock down assumptions to exactly 69% effective reduction of exposure behaviours among 69% of the population ( Figure 3C and D) . Under such precisely assumed conditions, the epidemic proceeds steadily with between 7 and 9 ICU cases per week over a decade, at the end of which national ICU capacity has never been exceeded and only 1085 deaths will have occurred. However, at the end of such a 10-year campaign, with no end in sight for at least several decades, only 0.5% of the population would have acquired hard-won immunity through prior infection, so the remainder of the population would remain just as vulnerable to a resurgent epidemic. 1 , intended to flatten the curve enough for national health system capacity to cope while herd immunity is acquired over the long term. All these simulations have identical input parameters to figure 1 except that no importation containment is assumed and the coverage and protective effectiveness of exposure behaviour reduction is assumed to be lower, at 68% (Panels A and B), 69% (Panels C and D) or 70% (Panels E and F). is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.