Fig. 9.

Comparison of outbreak levels caused by the future variant and the previous variant of SARS-CoV-2. (a) shows the size, peak, and duration of the outbreak caused by the future variant compared to the Omicron variant. We considered different values of the cross-immune protection against the new strain ${\eta }_2$ acquired after infection by previous strains and different values of the relative transmission ability ${\beta }_1$ of the new strain, as well as different time points for the emergence of the new strain. late invasion indicates that the new strain will emerge late in the transmission of the Omicron strains, with a delay of 150 days from other transmission conditions. (b) shows the ratio of the final size of the outbreak caused by the Omicron strain and the new strain. The immunity scale indicates the proportion of the population with a history of infection and cross-protection against the new strain. ${\eta }_2$ is the cross-immunization intensity. (c) shows the effect of the invasion time of the new strain, the strength of cross-immunity, and the relative transmission ability on the time of strain replacement, where Early invasion, Midterm invasion, and Late invasion represent the invasion of a new strain at 20, 90, and 170 days after the start of transmission of the previous strain, respectively, meanwhile they also represent the invasion of the new strain at the beginning of transmission, around the peak, and at the end of the last outbreak. (d) shows the effect of the timing of the emergence of a new competing variant and its relative transmission ability on the transmission dynamics of the previous strain.