RecruitingPhase 1Biological interventionA Vaccine (H2NVAC) Before Surgery for the Treatment of HER2-Expressing Ductal Carcinoma In SituThis phase Ib trial studies the side effects and best dose of a vaccine called H2NVAC before surgery in treating patients with HER2 expressing ductal carcinoma in situ. H2NVAC is a vaccine designed to stimulate specialized white blood cells in hopes of increasing immune response and protecting against breast cancer.