Since they launched their foundation in 2000, Bill and Melinda Gates have become America’s philanthropic golden couple — giving away more than $30 billion of their wealth and saving millions of lives in the process.

But their influence goes far beyond the work of their own foundation. The pair is credited with reinventing how philanthropy is done with their focus on concrete measurable goals and consensus-building between foundations, businesses, development groups and governments.

In 2010, Bill Gates teamed up with his friend Warren Buffet to launch a campaign — called The Giving Pledge — to convince other super wealthy people around the world to give away at least 50 percent of their money to charity. There are now nearly 130 billionaires with a net worth of more than $700 billion who have signed the pledge.

This year, the Gateses are rallying other global citizens — ordinary people — to get involved in charity work.

“Having individuals stand up and say I care about the rest of the world, I care about these inequalities and I’m going to hold my government accountable for what they do — that’s what we’re hoping will happen,” Melinda Gates said in a joint interview with her husband earlier this year.

Excerpts:

Q: This year is your foundation’s 15th anniversary. When you reflect on all the work you’ve done, what are you most proud of?

Melinda: The work in vaccines and immunizations has really been transformative in bringing down childhood deaths. The two biggest killers of children are diarrhea and pneumonia. We now have new vaccines in those two areas that we’ve been involved in getting created, bringing the prices down and trying to get the lag time down. When we got into this work, the lag time in getting a vaccine from the United States to somewhere like Kenya was 20 to 25 years. That’s down now to one to three years. That’s something we’re incredibly proud of.

Q: When do you think the developing world will be caught up to the developed world in terms of child health and infectious diseases like malaria and polio? Will it be in the next 15 years? At that point will you turn your attention to heart disease and cancer and other health problems that are seen right now as issues for older people in wealthier countries?

Bill Gates: In 15 years, we won’t be far enough along to make that switch. There will still be a lot of infectious disease. I’d say at the 30-year mark if things went well there’s a chance that this agenda will be largely done… [At that point] we hope the rich world would have very, very effective tools for all sorts of disease and we see it as part of our mission to see that they get out to everybody in the world faster than the natural market mechanism would make them available.

Q: You’ve donated a lot of money recently to the effort to fight Ebola. What do you think about what’s going on in West Africa and are you optimistic or pessimistic we will be able to get the situation under control?

Bill Gates: I don’t think Ebola will be a huge problem in the future. The biggest thing to worry about is some pathogen we’re not ready for and that is more infectious than Ebola. Ebola is a big tragedy and we’ve got to rebuild the primary health care system there, but you can imagine epidemics that would affect way more than 20,000 people. They could literally affect 20 million people.

Melinda Gates: Especially if it is airborne. I think the thing that Ebola highlights is how important it is to invest in the primary health system. The countries that are seeing the outbreak — these four countries — have very weak primary health systems and now they are crumbling. Whereas in Nigeria there was a functioning primary health system. When Ebola came into Lagos they immediately knew how to turn to an emergency response clinic. We got very lucky as a world that in a city with 22 million people we didn’t have a huge outbreak of Ebola.

Bill Gates: It was actually polio resources that were able to come in and do the contact tracing.

Q: At the World Economic Forum in Davos this year, Oxfam came out with a report that predicted that one percent of the world’s population would control more than 50 percent of the world’s wealth by 2016. How do you reconcile this rising inequality with the optimistic view you have about where things are headed?

Bill Gates: Inequality is a very important topic, and every country has to think about what kind of tax policies they have. Within a country there is a tendency, unless tax policies offset it, toward more inequality. And in a democracy that debate does go on. We do think philanthropy — although not by itself a total solution to the problem — we do think more philanthropy from the middle class, the upper class, to the people who have been super super lucky like ourselves is an element that works against this inequality. Making sure vaccines are there for every child, making sure reproductive health tools are there for every woman who wants them, solving the basic human needs for everybody. . . Philanthropy is not the big bulk of the dollars but the high risk, a lot of the innovation, a lot of the push comes from that element.

Melinda: I think it’s great to have it highlighted for people so that they are having this conversation, about how do you make the world more equal… If you look back at history, Carnegie highlighted the need for libraries to be a place where everyone could go to read if you didn’t have access to books. Philanthropy can be a place that’ll take a risk or point to areas to make sure they are the right government investments to reduce those inequalities.

Q: Since you started the Gates Foundation 15 years ago, a large number of other tech entrepreneurs have pledged to give away the majority of their wealth. Are there any specific people you are mentoring or working closely with? Approaches you admire in this new generation of philanthropists?

Gates: We have a group — the Giving Pledge group — where we get to learn from other people and they get to hear what we’re up to and it’s got quite an age range. I think Dustin [Moskovitz] is still 29. I think Mark [Zuckerberg] is about to turn 30. David Rockefeller is about to turn 100. So that’s our span.

We have yearly get-togethers and special sessions where people who are interested in medical research or K-12 education will get together. I think if you look at it as an industry, tech has a pretty good participation in terms of the people who have been very successful having philanthropic plans.

We work of course with Paul Allen on Ebola. Larry Ellison was super generous on polio. Mark Zuckerberg has gotten involved in education and he did some polio grants.

Melinda: I think the neat thing about this group is no matter what your age is everyone’s learning from each other. They are hearing about what one another’s failures have been, what one another’s successes have been, how people are looking at issues. One of the great topics we talked about this fall [at a Giving Pledge meeting] was on measurement and evaluation. How do you really measure that you’re getting the outcomes you want — which is really a very difficult thing to do? How do you set up a data system if the measurement systems aren’t there? How do you begin to do that in a developing country? Learning from one another is the whole goal of this group no matter what background people are coming from or what age they are.