We have known for years that vaccinations, including routine childhood vaccinations for diseases like measles, mumps and rubella prevent children from dying on a fairly massive scale. We also know that as a health intervention, most vaccines and vaccination programs are relatively inexpensive.  What was not well known, at least until recently, was the relationship between vaccine preventable illness and poverty.    Dr. Angela Chang lead a ground breaking study that shows how vaccines can be an effective tool to prevent individuals in the developing world from slipping down the income latter and into extreme poverty.   Dr. Angela Chang is a post doctoral fellow at the Institute of Health Metrics and Evaluation at the University of Washington. The study was published in the journal Health Affairs while she was a doctoral candidate at Harvard School of Public Health. It examines the relationship between what is known as "medical impoverishment" and vaccinations.   We kick off the conversation discussing what we mean by medical impoverishment before having a longer conversation about her findings.