SETH BERKLEY

You'd see little shallow graves, lined up, one after the other - babies. That's what happens when measles goes through a nutritionally deficient community. It's a horrible disease, and it spreads incredibly efficiently.

New vaccines are being developed all the time, which could save many more lives and dramatically improve people's health. And this goes beyond the traditional burden of childhood infectious diseases.

History will not judge HIV/AIDS kindly... the harshest words will be reserved for how the world responded, or rather failed to respond, to the epidemic.

Measles is probably the best argument for why there needs to be global health, and why we have to think about it as a global public good. Because in a sense, measles is the canary in the coal mine for immunization. It is, you know, highly transmissible. The vaccine costs 15 cents, so it's not - you know, shouldn't be an issue in terms of cost.

Healthy children are more likely to attend school and are better able to learn. Healthy workers are more productive. More productive economies mean greater stability in developing countries and improved security in the West.

When AIDS first appeared, people didn't know what it was. You'll remember that it affected mostly young gay men - it was actually called GRID for a short period of time: Gay-Related Immunodeficiency Syndrome - and people thought it actually might be recreational drugs or other types of toxins.

I was a serial monogamist.

The return on investment in global health is tremendous, and the biggest bang for the buck comes from vaccines. Vaccines are among the most successful and cost-effective health investments in history.

Investments in immunization yield a rate of return on a par with educating our children - and higher than nearly any other development intervention.

Now, when you get a viral infection, what normally happens is it takes days or weeks for your body to fight back at full strength, and that might be too late. When you're pre-immunized, what happens is you have forces in your body pre-trained to recognize and defeat specific foes. So that's really how vaccines work.

Leadership is about vision and responsibility, not power.

You can't stop wars to build tertiary teaching hospitals, but you can say, 'Let's stop for a couple of days to immunise the kids.' It has been done.

I wish we could have state-of-the-art hospitals in every corner of the earth... but realistically, it's going to be a while before that can happen. But we can immunise every kid on earth, and we can prevent these diseases. It's only a matter of political will, a little bit of money and some systems to do it.

The virus that causes AIDS is the trickiest pathogen scientists have ever confronted. It mutates furiously, it has decoys to evade the immune system, it attacks the very cells that are trying to fight it, and it quickly hides itself in your genome.

Now, you might think of flu as just a really bad cold, but it can be a death sentence. Every year, 36,000 people in the United States die of seasonal flu. In the developing world, the data is much sketchier, but the death toll is almost certainly higher.

I love science, and I believe in it. I have a faith that science can solve problems and make the world a better place.

When it comes to providing aid, developing innovations, and making bold steps that change the course of history, the United States is usually on the front lines.

For just a few dollars a dose, vaccines save lives and help reduce poverty. Unlike medical treatment, they provide a lifetime of protection from deadly and debilitating disease. They are safe and effective. They cut healthcare and treatment costs, reduce the number of hospital visits, and ensure healthier children, families and communities.

In large part, thanks to widespread immunization, the number of young children dying each year has declined significantly, from approximately 14 million in 1979 to slightly less than eight million in 2010.

Science is one of the comparative advantages of our knowledge-based economy, and focusing on our prowess in providing better tools to address diseases of poverty is one of the best forms of foreign aid.

We've actually eliminated Type II polio in the world, at least as far as we can tell.

Children who are healthy - and have adequate nutrition - are much more likely to attend school. People who finish school and do well have higher earning potential in their adult lives.

If you want to know the value of vaccines, just spend some time in a clinic in Africa. The faces of the mothers and fathers say it all: vaccines prevent illness and save lives.

As cities get bigger, our best defence will be to prevent outbreaks in the first place by building better public health systems, improving childhood immunisation through better routine immunisation and pre-emptive vaccination campaigns.

Land degradation, rising sea levels, famine, and conflict will continue to drive people from their homes and towards cities, with megacities like Mexico City and Lagos becoming increasingly common in some of the poorest parts of the world.