Probably the best example is the influenza vaccine, which for decades was made in hen's eggs. Now we have a mammalian-cell-based vaccine, which in many ways is an easier and more reliable way to make the vaccine. The challenge, however, was that this is an entirely new product. Therefore, both the product, the manufacturing protocol, and the building in which the product is made have to be licensed as a new product, which is an enormously expensive thing to do for what is not a big ticket item. Vaccine profits will always pale in comparison to drugs as vaccines are given just once or at most a few times during one's lifetime, whereas some drugs are given every day.