96 from registration to launch) [11]. Decision to develop a vaccine is based on an analysis of the competitive landscape, and of push and pull forces. A vaccine is developed either because of a clear demand, a “pull”, for the vaccine by the market, or because it becomes technically and operationally feasible,

a “push”. “Push” forces involve scientific and technological advances, management and coordination support, and the availability of research and find more development funding. “Pull” forces reflect the potential value and profitability of a future product. In practice, the development of vaccines is dependent on the concerted action of both push and pull forces [12]. Only those vaccines that are the most promising in terms of technical feasibility, strong patent protection, and potential market size will be taken forward into development. Industry operates on a “go/no go” decision framework that is revisited many times along the R&D pathway. Multiple strategic go/no-go decisions are to be made about whether to continue to invest time, money, and human resources on a particular vaccine at key points in the vaccine development process: decision to initiate the vaccine development; decision to move from preclinical research to clinical development; decision to commit to phase III clinical trials. Except maybe for the decision Fludarabine to go to registration and launch that is based

essentially on the results of phase III clinical studies, these decisions derive from a series of ‘best bets’, based on a review of push and pull forces and on an evaluation of both development costs and risks and of the vaccine portfolio. Additional risky decisions also have to be made such as building a production facility for a new vaccine. With few exceptions, each vaccine requires a different plant because of unique manufacturing and regulatory requirements. Since it takes about 5 years to build and validate a new vaccine production facility, this bet on the future must be made when the new vaccine is still in clinical development and its efficacy and safety have not yet been fully demonstrated. Methisazone Reticence to take a chance on the future may generate a gap between licensure and product launch [2] and [9].

During the past two decades, mechanisms have been established to accelerate product development (‘push’ mechanisms), or to create more attractive markets (‘pull’ mechanisms) [13]. Government organizations such as the NIAID [14], [15] and [16], USAID [17] in the USA, European Programs [18], [19] and [20], GAVI Alliance [21], the Bill and Melinda Gates Foundation [22] are playing an increasing role in the development and implementation of vaccines. Product Development Partnerships (PDPs) bring together specialized knowledge and resources as well as early capital investment to reduce the scientific technical and financial risks. Market incentives include the development of innovative financing mechanisms, essentially for vaccines intended for developing countries.