At the World Economic Forum, Melinda and I announced that our foundation was making a long-term commitment to invest $10 billion to help research, develop, and deliver vaccines for the world’s poorest countries.

In my foundation annual letter, I talked about some important new vaccine developments and what we need to do next to save millions of children. Melinda and I also recently gave a speech to government leaders in Washington D.C. where we highlighted people who are Living Proof that vaccines save lives.

I’ve always believed in the miracle of vaccines. My recent travels along with progress on things like a malaria vaccine have convinced me to shift more of the foundation’s global health resources to vaccine research and delivery.

As a big believer in innovation, I see vaccines as a fascinating example of a high-risk idea with a huge pay-off. In 1796, Edward Jenner, an English physician, noticed that dairymaids who suffered from a disease called cowpox were not getting smallpox. So he extracted fluid from a blister on a dairymaid and injected an 8-year old boy with it—the very first vaccination. Sure enough, that little boy, James Phipps, became immune to smallpox too.

As a businessman, vaccines are appealing because they have one of the best returns on investment in health. (Except for maybe breastfeeding, which is free and very beneficial to long-term health and cognitive development.)

The lives of at least 20 million children have been saved by vaccines in the last two decades.

The price of immunizing a child against diphtheria, tetanus, and pertussis (whooping cough) is now less than 50 cents.

Over 77 percent of children in the poorest countries of the world are now protected from these diseases. Immunizing children against these three diseases plus measles prevents more than 2.5 million deaths each year.

Although many vaccines have been used regularly in the rich world for years, they are just now becoming widely available for children in the developing world.

Scientists have invented new vaccines for diarrhea and pneumonia, two of the biggest killers of kids in developing countries. These life-saving vaccines won’t reach children in need without big commitments from donor governments.

I’ve given kids the polio vaccine myself—it’s just a couple drops in the mouth. It’s quite magical knowing you are helping prevent a terrible, disfiguring disease.

As a parent, I have a choice to provide my children with something that has the potential to prevent illness or even death. I want parents everywhere to have that same chance.