What is the relationship between viral prospecting in animals and medical countermeasure development?

In recent decades, surveillance in non-human animals has aimed to detect novel viruses before they "spill over" to humans. However, the extent to which these viral prospecting efforts have enhanced outbreak preparedness remains poorly characterized, especially in terms of whether they are necessary, sufficient, or feasible to spur vaccine development. We find that several viruses which pose known threats to people lack approved vaccines, and known viruses discovered in human patients before 2000 have caused most major 21st-century outbreaks. With Filoviridae as a case study, we show there is little evidence that viral prospecting has accelerated vaccine or drug development or that systematically discovering novel zoonotic viruses in animal hosts before they cause human outbreaks has been feasible. These results suggest that surveillance for novel viral zoonoses does not accelerate vaccine development and underscore questions about its importance for outbreak preparedness. We consider limitations to these conclusions and alternative approaches to preparedness and response.IMPORTANCESampling in animal populations to detect novel viruses before they infect humans has been a major activity justified by several considerations, notably by the idea that finding such viruses will stimulate the development of medical countermeasures such as vaccines. This article examines the evidence that such research leads to earlier vaccine development and finds the evidence lacking. This is important because, in an era of scarce resources and biosafety considerations for researchers, efforts should be directed to those activities most likely to yield the desired outcomes.