The malaria vaccine in humanist terms is the biggest need. But it gets virtually no funding. But if you are working on male baldness or other things you get an order of magnitude more research funding because of the voice in the marketplace than something like malaria.

"For helping out the poorest we still need very simple things -- keeping vaccines refrigerated. But where there's no electricity, delivering diesel or propane is hard, we have tens of thousands of children who die because the vaccine supply chain doesn't have these tools," Gates said. "We still have a lot of deaths that really shouldn't take place."

He hopes to see the mortality of children under the age of five to reduce from seven million per year to below three million by 2030.

When asked by an audience member whether it was possible to build a social company that is also profitable, Gates said: "There are a number of areas where you can build a product that has value in the rich world, for middle income countries and the poorest. Ideally you create a business model that lets you get your margin from the rich countries and the middle income countries, or through tiering customers in developing countries."

He cited eye clinics in India that offer free lens replacement and other treatments to the poor but charges those who can afford it as a good example of a tiered system.

He added that in the last few years in the US, computer science has seen enrolment go back to 1999 levels, but that the sciences broadly had big deficits as well as a lack of racial diversity and gender diversity.

"We are failing to get women in. There must be something about how we teach the sciences that makes them not seem that attractive."