The world is closer than ever before to wiping out polio.

Last year, the world saw the fewest number of polio cases—just 21, according to the latest figures.

That’s incredible, especially when you consider that just 30 years ago, there were 350,000 cases of polio per year worldwide.

The heroes who have made this progress possible are the millions of vaccinators who have gone door to door to immunize more than 2.5 billion children. Thanks to their work 16 million people who would have been paralyzed are walking today.

But the job is not over. The few polio cases left can be found in three countries: Afghanistan, Pakistan, and Nigeria. Many of the vaccinators in these countries continue to work in difficult and dangerous conditions to protect children from this paralyzing disease.

They deserve our thanks and support as we work toward the day when no child is at risk of polio.