Ronan at 2 years old. "I know Ronan's purpose in life was to shed light on this disease," says his mother, Maya Thompson. "This is why I will continue to fight for childhood cancer for the rest of my life."
Courtesy of Maya Thompson
A boy in Lima, Peru, receives a hepatitis B vaccine during an immunization drive in 2008. The United Nations is considering a ban on the preservative thimerosal, which is often used in hepatitis B and other vaccines in developing countries.