In a vaccine development program, the probability of success at each transition decreases, even though the actual probability of moving from one phase to another can be 50–80% (Figure 1). Many compounds and vaccine candidates are screened out even before they get into preclinical studies. Developers can implement different approaches to reduce product failure risk before a program gets expensive, including Establishing a product development plan (PDP) Identifying and mitigating risk with gap analysis Learning from the mistakes of others…