Stated more simply: It is good that children in poor countries are dying because if they had lived then they would have created more poverty.
How is this getting any upvotes? marciovm, Gates isn't spending this money to play up his image to the American public and to tug at America's heart strings. He's doing this because it's right. Giving people vaccines to live is right. Letting them die because it might create less poverty isn't - it's missing the point that all lives are important.
I completely agree that empowering the economies of developing nations is a very high priority. Higher GDP's lead to longer life, lower infant mortality, more education, less children per mother (because the opportunity cost of having a child is higher once the mother gets a high salary), etc. However, researching vaccines is just as important and necessary for developing countries that are crippled by HIV/AIDS, malaria and tuberculosis.