SEATTLE, Jan. 31 (UPI) -- Bill Gates says vaccines he calls the most effective and cost-effective health tools ever invented are the best investment to improve the human condition.
In his annual letter on philanthropic campaigns, the head of Microsoft said the world is on the verge of eradicating polio, approaching the second time in history a human disease has successfully been eradicated, The Seattle Times reported Sunday. Smallpox was ruled officially eliminated in 1979.