She was the lead for HIV/AIDS vaccines at OAR and advanced the NIH AIDS vaccine program through supporting vaccine trials and developing a vaccine scholars program designed to train young scientists.[2] Mathieson was an advocate for young people, women, and early-career investigators.[3][5] Her colleagues knew her as an international leader in the HIV vaccine field and a supporter of research to prevent HIV and improve the health and outcomes of people living with HIV. Mathieson retired from the National Institutes of Health on December 29, 2017.