The study will be a multi-center, prospective, randomized, single-blinded, placebo-controlled Phase II trial of Herceptin + NeuVax(TM) vaccine (E75 peptide/granulocyte macrophage-colony stimulating factor) (GM-CSF) versus Herceptin + GM-CSF alone. The target study population is node-positive (NP) (or node-negative [NN] if negative for both ER and PR) breast cancer patients with HER2 1+ and 2+ expressing tumors who are disease-free after standard of care therapy. Disease-free subjects after standard of care multi-modality therapy will be screened and HLA-typed. E75 is a CD8-eliciting peptide vaccine that was restricted to HLA-A2+ or HLA-A3+ patients (approximately two-thirds of the US population), and has been extended to HLA-A24+ and HLA-A26+ as well.