Modeling the impact of anthrax vaccination on buffalo outbreak dynamics in northern Vietnam.

A widespread and underreported zoonosis, anthrax is a severe infectious disease of significant public health concern for humans, livestock, and wildlife. In this study, we used historical data from 1991 to 2020 from northern Vietnam and a simulation model to investigate the effects of different vaccination strategies on livestock outbreaks. We developed a novel approach combining semi-synthetic data generation and a sliding windows model fitting routine to estimate disease transmission parameters from surveillance data and address the temporal mismatch between pathogen transmission dynamics and disease reporting. Results showed that vaccination leads to a significant reduction in buffalo mortality, with reactive and increasing vaccination campaigns having the largest impact in reducing outbreak size. Reactive and decreasing vaccination campaigns initially controlled outbreaks, but mortality increased as soon as vaccination ceased, highlighting the need for sustained, long-term vaccination. In scenarios where populations had high natural immunity, the impact of vaccination was less pronounced, though still evident, suggesting that prioritizing vaccination efforts for more susceptible populations may provide a greater return on investment in outbreak prevention and control. Simulation models can offer valuable insights into vaccination and control strategies, providing tools to compare and evaluate potential outbreak scenarios. Our findings underscore the value of mathematical and simulation approaches to overcome data challenges and underreporting in global disease management for anthrax and other neglected diseases. We highlight the importance of continued investment in surveillance and modeling efforts, while providing a practical approach to optimize the use of existing data in Vietnam and similar settings.