By now you probably know that vaccines are one of the best investments in global health. Today we have highly cost-effective vaccines for pneumonia, diarrhea, and meningitis, which account for over 2.5 million child deaths each year.

But cost-effectiveness isn’t enough. We need to have enough money to purchase and deliver these vaccines. In other words, it’s important that they be both cost-effective (good value for money) and affordable (within a country’s financial means).

That’s where the GAVI Alliance comes in. GAVI is helping to finance new vaccines for poor countries around the world. Donors give money to GAVI, and GAVI then works with UNICEF to purchase vaccines on behalf of these countries. Recipient countries only have to pay what they can afford, but this amount increases over time as their economic situation improves. The goal is for every country to “graduate” from GAVI support at some point in the future.

Unfortunately, GAVI is facing a financial shortfall that is preventing it from purchasing these vaccines. The global community is going to tackle this challenge at a “pledging meeting” in London in June, by asking donors to commit more resources to GAVI, recipient countries to allocate more of their own resources to immunization, and vaccine manufacturers to make their vaccines available to GAVI countries at the lowest sustainable price.

We’re counting on a successful pledging meeting in June, as it will set the stage for other vaccines, such as a new vaccine against HPV (a cause of cervical cancer in girls), an injectable vaccine against polio, and vaccines in development against malaria and tuberculosis.

Now is the time for the world to ensure that every child has a shot at a long and healthy life. Here’s more from Bill, who devoted much of his annual letter to the power of vaccines.