Optimizing the delivery of self-disseminating vaccines in fluctuating wildlife populations

Author summary Pathogens such as Ebola, rabies, and Lassa virus that usually infect wildlife can jump to the human population. In the worst case, this can lead to outbreaks or pandemics such as happened in 2014 with Ebola and 2019 with SARS-CoV-2. One approach to mitigate the threat of pathogens spilling into the human population is to proactively vaccinate wildlife harboring these pathogens before the pathogens infect humans. With traditional vaccines, administering enough vaccines to the wildlife population to limit pathogen spread is challenging. To address this challenge, recent technological advances have allowed the development of vaccines that allow some degree of spread of the vaccine from animal to animal. However, for a vaccination campaign using these self-disseminating vaccines to be implemented successfully, we need to know when vaccines should be administered. We used mathematical models to explore how the reservoir host’s population ecology and properties of the vaccine affect the success of a vaccination campaign. Our results demonstrate that the timing of vaccine delivery relative to seasonal reproduction can make or break the success of vaccination programs. The effectiveness of self-disseminating vaccines is optimized by introducing vaccine after the peak of seasonal reproduction when the number of animals available for vaccination is highest.