Fig. 1: Infection burden for illustrative variant of concern (VOC) scenarios, produced using the parsimonious SARS-CoV-2 transmission model.
We considered three putative VOCs with differing transmissibility and immune-escape characteristics: more transmissible (VOC MT, blue line with square markers), equal transmissibility with immune escape (VOC E, orange line with plus sign markers), less transmissible with immune escape (VOC LT+E, yellow line with circle markers). We also present temporal dynamics for resident variants in the absence of any VOC being introduced (black line with no markers). Additionally, in panels a and c, we represent the vaccine uptake in the population through time via background shading, the transition time into Step 4 of the relaxation roadmap by the vertical solid line, and we state the assumed R excluding immunity values for resident variants (Rexcl) throughout Steps 3 and 4, respectively. a VOC infectious prevalence over time. In each scenario, alongside resident variants, we introduced one of the VOCs on 17th May 2021 with 2000 initial infecteds. c Instantaneous R of a VOC accounting for population-level immunity (y axis) calculated at the time of its introduction (x axis). For the “Resident variants with no VOCs” scenario, the displayed profile corresponds to the instantaneous R with immunity of resident variants. In panels b and d, we explore the sensitivity of two epidemiological outcomes to the relative transmissibility of the VOC compared with resident variants and the proportional efficacy (vaccine and natural immunity) against the VOC: b outbreak final size; d peak in VOC-infection cases.
