Fig. 4.

Impact of a more-transmissible variant on post-second-wave dynamics. Following the second wave, we assumed the emergence of a novel virus with basic reproduction number, R₀⁽³⁾>2.5. Again to control for other factors, we assume that those previously exposed remain immune to this novel virus, and further that prior immunity wanes on a timescale longer than modelled here. (A) Potential third-wave dynamics arising from the example of a novel virus with R₀⁽³⁾=5.4. (B) How the size of the third wave would vary with R₀⁽³⁾. For the (purely illustrative) background parameters assumed here, a novel, more-transmissible virus would need to have R₀⁽³⁾ at least 4.5, in order to cause a substantial third wave.