The research I have conducted has been focused on epidemiologic aspects of viral vaccine development and prevention of perinatal HIV transmission. A major project has been to identify the molecular epidemiology of factors affecting the immunogenicity of oral polio vaccine (OPV) among children living in developing areas of the world, where OPV immunogenicity is poor. We have identified several factors which affect the poor immunogenicity of OPV and will conduct clinical studies to attempt to improve immunogenicity. We are now working on ways to understand the transmission and circulation of polio vaccine derived viruses, which may cause polio, and how to use this information in global eradication of polio. I also work on perinatal HIV infection, including strategies to prevent breastfeeding transmission in developing settings as well as understanding how to maximize prevention strategies among pregnant women in developed countries.