<qa>  What is the HER2 cytotoxic T lymphocyte peptide-based vaccine?I. To quantify and characterize human epidermal growth factor receptor 2 HER2-specific central memory T cell TCM and effector memory T cell TEM subsets in peripheral blood mononuclear cell PBMC of patients vaccinated with a HER2 cytotoxic T lymphocyte CTL peptide-based vaccine. 