Quantifying the impact of bacterial vaccines against antibiotic resistance: accounting for transmission and selection dynamics

Vaccines, by reducing bacterial infection, transmission and/or colonisation, are promising investments against the global rise of antibiotic resistance (ABR). From a public health perspective, while efforts are put in developing bacterial vaccines, anticipating their potential impact on ABR is essential. We developed a compartmental model formalising inter-individual transmission and selection pressure through both bystander and targeted antibiotic exposure. Following a mathematical analysis of the model's equilibrium points, we explored the impact of different vaccines through simulations for two bacterial types. In simulations, vaccines consistently reduced infection incidence, although to varying extents. For S. aureus, a vaccine reducing acquisition rate, infection rate and colonisation duration by 60% at 70% coverage reduced total infections by 80%, while this reduction was only of 48% for E. coli. The impact on the resistance proportion among colonised differed markedly: this same vaccine increased it by 11% for S. aureus, while decreasing it by 8% for E. coli. Overall, our results highlight that population level impact on ABR strongly depends on the vaccine mechanism of action. The proposed model, which gathers the main drivers involved, provides a general framework that can be adapted to a wide range of bacterial pathogens and vaccines.