Sick people receive vaccines for free or very cheap
Sick people gets hope of survival to disease, hope which wasn’t previously available.
Sick people ask their governments to continue receiving vaccines.
People providing vacciones now are charging a lot more to said governments.
Profit (which was the whole point, and not any “humanitarian” notions.)
And the market wasn’t there, because unless there’s some way to create high demand and guaranteed payment in poor countries, there’s no profit in said vaccines (or any medication, for that matter; do you see any multinational farmaceutical companies giving much thought to the creation of medicine to cure Chagas disease? And it’s endemic in many areas of South America. But those are poor areas, so the is no profit there).