Why certain vaccines have been delayed or not developed at all.

Vaccine development is a long process, with the time from early research to licensure steadily increasing. At one time the process took about ten years; now it takes closer to fifteen to twenty years. The process begins with investigators in universities or biotech firms who have an idea. However, to take things further, there must be a vaccine manufacturer, a regulatory authority ready to give permission for the use of the vaccine, and public health authorities that will recommend and foster vaccination.