SIRV model: voluntary vaccination driven by perceived risk
2.55.00.30
In the SIRV model with behavioral feedback, susceptibles vaccinate at rate α·σ(κ·I) where σ is a sigmoid and κ is risk sensitivity. High R₀ drives more voluntary vaccination, creating a "free-riding" equilibrium: rational non-vaccinators benefit from herd immunity without cost — until the epidemic overshoots.