Ouch, Yeddi! I haven't seen anyone eating dirtcakes in third world countries personally
Haiti: Mud cakes become staple diet as cost of food soars beyond a family's reach | World news | The Guardian

What would you do?
Based on the idea that there wouldn't be any warlords or other similar factions coming in to destroy it all...

We do live in the 21st century. We have access to new and improving technology, it's time to invest in those instead of falling back into options that are archaic and don't serve the current circumstances (i.e. the manual digging of wells). Wells serve as a good stop gap measure to provide water while other infrastructure is built, but they shouldn't be the goal.

These are goals that would actually make a difference:
Third World water solutions sought
Desert Agriculture and Agroforestry | Mission 2014: Feeding the World
Growfish News Article - Israelis helping to perfect fish farming in the desert - Israel - Aug 27, 2002

That's just to start with. Even if vaccines were 100% effective on 100% of people given them (which we know they're not, even you can't say they work all of the time) that still only protects the immediate population. Infrastructure provides for the immediate as well as future populations - a much better way of spending.