Paradox of vaccination in the context of avian influenza strain mutation

Vaccination is a widely employed strategy for controlling avian influenza; however, a significant challenge is the potential mutation of vaccine-sensitive strains into vaccine-resistant variants. In this study, we introduce an innovative model that incorporates mutation dynamics to assess the effectiveness of vaccination programs. We derive the basic reproduction number and examine the existence and stability of equilibria. Conditions for evaluating vaccine effectiveness are established. Our theoretical and simulation results reveal novel insights compared to previous investigations. Specifically, we observe that mutations lead to complex and counterintuitive outcomes regarding vaccination effectiveness. As vaccination coverage increases, the total number of infections initially decreases before subsequently increasing. In scenarios characterized by high mutation rates and low vaccine efficacy, vaccination initiatives can promote disease transmission. Sensitivity analyses indicate that enhancing vaccine effectiveness and reducing strain transmission rates can help mitigate disease propagation. Furthermore, non-pharmaceutical interventions, such as selective culling, prove effective in controlling outbreaks. Our findings contribute valuable insights into the evaluation of vaccination program effectiveness.