A partially effective malaria vaccination that reduces incidence in children by over half.

This is a game changer for Africa.  No, it will not give them stable governments, good roads, or accessible ports.  But it's hard to overstate the impact of disease burden on sub-Saharan Africa.  This sort of vaccination also has big external benefits--by reducing the pool of infected carriers mosquitoes attack, it will significantly cut down on the overall incidence even among those who aren't vaccinated.  It's still got a ways to go through trials, but if it works, this will do more for Africa than all the development money of the last decade.