David Vetter was born without a functioning immune system and spent his life in a bubble that protected him from germs. He died at age 12 in 1984. Scientists are using gene therapy to treat the disorder so that children can live normally.
Syrian boys line up to get the polio vaccine at a refugee camp in Sidon, Lebanon, on Nov. 7. The Lebanese government plans to vaccinate all kids under age 5 for the virus, including Syrian refugees.