HLA-A2+/A3+/A24+/or A26+ patients who meet all other eligibility criteria will be randomized to receive Herceptin + NeuVax vaccine or Herceptin + GM-CSF alone. For both groups, Herceptin will be given every three weeks as monotherapy for one year, to be given upon completion of standard of care chemotherapy/radiotherapy. The first Herceptin infusion must be given no sooner than three weeks and no later than 12 weeks after completion of chemotherapy/radiotherapy. Herceptin will be dosed at the recommended initial loading dose of 8 mg/kg and at recommended maintenance doses of 6 mg/kg q3wk. Herceptin will be administered as described in Section 4.3. Patients randomized to the NeuVax vaccine arm will receive vaccinations of E75 peptide (1000 mcg) and GM-CSF (250 mcg) administered intradermally every three weeks for six total vaccinations, 30-120 minutes after completion of Herceptin infusion. The NeuVax vaccine series will begin immediately after completion of the third Herceptin infusion. In extenuating circumstances, the first vaccination may be delayed to the fourth or fifth Herceptin infusion with prior approval from the Principal Investigator. Those patients randomized to the GM-CSF alone arm will receive vaccinations of GM-CSF (250 mcg) administered in an identical manner to those receiving NeuVax vaccine. Patients will be blinded as to whether they are receiving NeuVax vaccine or GM-CSF alone.