A variety of immunologically based vaccines, such as those derived from cell proteins or peptides, DNA and virus, and dendritic cells, demonstrate the ability to prevent mammary carcinoma in HER2 transgenic mice, suggesting that their potential usefulness in adjuvant therapy of HER2-positive tumors to prevent the development of invasive breast cancer from HER2-positive DCIS as well as of metastases. The gene discussed is ERBB2; the disease is breast carcinoma.