Dr. Althaf I. Hussain, a Principal Scientist and Team Leader with Medimmune in Santa Clara, California in the Bio-Pharmaceutical Development Department will visit the Department of Health Sciences, College of Arts and Sciences to give a lecture on Endogenous Retroviruses in Vaccines: Safety Issues and Cell Culture derived Influenza Vaccine. Currently licensed vaccines propagated in chicken eggs, cells and embryos including measles and mumps vaccines and Yellow Fever (YF) vaccines show evidence of two types of retrovirus particles, the endogenous avian retrovirus (EAV) and the endogenous avian leukosis virus (ALV-E). This presentation summarizes the investigations on substrate -derived avian retrovirus contamination in MMR & YF vaccines. The absence of evidence of infection with endogenous avian retroviruses in MMR and YF vaccine recipients suggests low risks for transmission of these viruses, supporting the safety of these vaccines.