This phase II trial studies how well TPIV100 and sargramostim work in treating patients with HER2 positive, stage II-III breast cancer that has residual disease after chemotherapy prior to surgery. It also studies why some HER2 positive breast cancer patients respond better to chemotherapy in combination with trastuzumab and pertuzumab. TPIV100 is a type of vaccine made from HER2 peptide that may help the body build an effective immune response to kill tumor cells that express HER2. Sargramostim increases the number of white blood cells in the body following chemotherapy for certain types of cancer and is used to alert the immune system. It is not yet known if TPIV100 and sargramostim will work better in treating patients with HER2 positive, stage II-III breast cancer.