As Tachi Yamada, president of global health at the Bill & Melinda Gates Foundation, prepares to leave the foundation this month, Nature News interviewed him about his work at the Gates Foundation and his predictions for global health.

“Most people in the developing world, particularly in South Asia, but also in sub-Saharan Africa, access care through the private sector and pay out of pocket. It’s a challenge to know how to impact that sector because most of our programmes in global health are meant to be run through the public sector and the government,” Yamada said in response to a question about the biggest challenge in the field of global health (Hayden, 6/21).