To add to NoKnees, vaccines are notoriously unprofitable endeavors. Take Ebola. Lots of development costs, and a very small, uncertain, POOR, market. Maybe there will be an outbreak, probably not. Not many people in the market, and the majority are in no position to pay for a fairly priced vaccine. So a company would have to make, store (and destroy and remake continuously to keep vaccine available just in case). Who would do that?
