It's a question of maximizing short term vs. long term good.  If you took combine 10 billion with a little leverage you could build ~(20 GW) worth of electric power in a self sustaining fashion that would pay for its replacement when the time came.  If you setup the right foundation that focused on growth you could probably replace all of the worlds coal power plants in ~150 years.  Or you can spending that money now, and vaccinate a large number of people for a low cost per person and dramatically reduce a specific type of suffering for a reasonable amount of time.