Furthermore, vaccination of mice with HER2 peptide alone or in combination with GM‐CSF, a common adjuvant for breast cancer peptide vaccines in the clinic, failed to induce strong HER2‐specific responses (Figure 4e) or the increases in serum cytokines that are seen in response to the α‐GalCer‐HER2 vaccine (Supplementary figure 5b). Here, ERBB2 is linked to breast cancer.