Figure 4.

Effect of vaccine humoral response on optimal epsilon. Sexual behaviour groups: superspreaders (yellow), casual (purple) and short (red). (a) The oncogene expression needed for persistent circulation, , with respect to the strength of the antibody response, δ_vac. Generally, increases with a stronger humoral response. Note that above each line are ɛ values that can also circulate (with R₀ values more than 1). (b) The derivative at for various δ_vac. The strength of selection for higher epsilon is stronger in immunodeficient hosts (dashed lines) in both casual and superspreader groups. Higher δ_vac implies slower selection towards . (c) The effect of vaccine-induced clearance time on optimal epsilon. Each line represents the oncogene expression needed for persistent circulation, , in a particular sex group, thus the shaded region above represents ɛ values that have R₀ values higher than 1. The oncogene expression needed for in the vaccinated host depends on how quickly vaccine-induced clearance happens. At Z₀ = 10⁻⁴, the vaccinated host sheds virus for about 150 days, and at Z₀ = 1 the vaccinated host shed the virus for 50 days. For all three sexual behaviour groups, if the challenge infection is cleared quickly (high Z₀) then a higher is favoured, but if the infection is cleared in under 50 days then even high oncogene expression cannot help the virus from escaping the vaccine.