As I traveled in Angola this week, I’m struck by the two faces I saw. While Angola enjoys the fastest-growing economy in Africa, it also suffers from the highest infant mortality rate in the world. Nearly one in five babies won’t live to be a year. What saddens me is that we have the vaccines to protect these children from terrible diseases, but the vaccines aren’t reaching them.

These two faces of Angola became very real during my visit to the Kikolo Communa in Cacuaco, an urban slum in Luanda. Twin girls of about 18 months greeted me at the entrance to their humble home. Helena was walking. Georgina, affectionately called Nzuzi by her parents, could only scoot on the dirt ground. Her leg was paralyzed from polio, and she will never be able to walk.

Polio has re-emerged as a threat to Angola’s health and prosperity. Areas considered polio-free as recently as 2005 experienced a significant outbreak in 2010. While the country started an aggressive vaccination campaign to stop the disease from spreading, more remains to be done.

Helena was lucky enough to escape the polio virus. Maybe she will become a school teacher like her father. But twin sister Georgina faces an uncertain life—one that will forever be shaped by a disease preventable with only a few doses of vaccine.

The elimination of polio in Angola is a huge responsibility—one that is now being taken seriously by the Angolan president, minister of health, governors, and partners. We are all accountable for success or failure. The lives of young children throughout the world are at stake.