Carl Krawitt has watched his son, Rhett, now 6, fight leukemia for the past 4 1/2 years. For more than three of those years, Rhett has undergone round after round of chemotherapy. Last year he finished chemotherapy, and doctors say he is in remission. Now, there's a new threat, one that the family should not have to worry about: measles. Rhett cannot be vaccinated, because his immune system is still rebuilding. It may be months more before his body is healthy enough to get all his immunizations. Until then, he depends on everyone around him for protection — what's known...
