Summary Infectious diseases, including Hepatitis C (HCV) and HIV, remain important health problems among Veterans. Development of vaccines for infectious diseases is therefore a key priority. Immunologic memory is a cardinal feature of adaptive immunity and an important goal of vaccination strategies. Traditional vaccination strategies are very effective at generating neutralizing antibodies, but not effective T cell memory. A key reason for the current lack of effective vaccines against many infectious diseases is that we do not yet know how to make vaccines that generate robust T cell memory. Thus, a fundamental understanding of how memory cells are formed is a crucial first step in rational vaccine design for infectious diseases.