Three decades ago, men stood on the surface of the moon and gazed back in solemn wonder at the earth. In that astonishing moment, we saw our small planet as it really is: one world, floating in the darkness of space, improbably lush with life.

Unfortunately, amid the complexities and contradictions of human society, it’s still easy to forget that we are one world. Vast disparities of wealth and opportunity divide us. The lives of an impoverished family in Bangladesh or Bogotá couldn’t seem more distant from those of a wealthy family in Tokyo or San Francisco.

Matters of Life and Death

Nowhere are the disparities more shocking than when it comes to health. Infectious diseases that have been banished from the most fortunate nations continue to kill millions among the poorest people on the planet--illnesses that can easily be prevented with a vaccine or a safe drug. Infant mortality is a rare and tragic event in the developed world; in the developing world it remains an everyday occurrence. In some places, one in five children dies before the age of five. As life expectancy continues to rise among the richest countries, it has actually fallen among some of the poorest.

Enormous Challenges and Opportunities

Today there is a growing sense that this inequity cannot be allowed to continue. The wonders and promise of modern medicine must reach everyone, not just a privileged few.

The quest to give everyone on the planet a fair chance at a healthy life is enormously complex. It involves science, economics, politics, ethics, environmentalism, psychology, culture, education, activism, and much more. The work requires the cooperation of an astonishingly diverse group of people--from microbiologists and pharmaceutical scientists to statisticians and community activists, from epidemiologists tracking the footprints of a new disease to barefoot volunteers bringing vaccines into remote rainforests. Public health is conducted at the highest levels of government and in the most remote rural villages, by some of the world’s wealthiest philanthropists and some of the poorest people on the planet.

Unifying all of these efforts is the simple belief that every single human life matters. All people should have access to the basic essentials of good health, whoever they are, wherever they were born. Those of us with the ability to provide life-saving vaccines and medications to the world’s least fortunate—and to conduct research and develop new medicines—can and should do much more.