Upon completion of the vaccination series, booster inoculations (same dose and route) will be administered every six months x4 for total combination (Herceptin and vaccine) treatment duration of 30 months. The first booster inoculation will occur with the final Herceptin infusion, with subsequent boosters timed every six months from the first booster. Booster inoculations will occur for patients randomized to receive E75/GM-CSF as well as patients randomized to receive GM-CSF alone, and will consist of the same treatment drugs and dosing (i.e. E75/GM-CSF patients will be boosted with E75/GM-CSF while GM-CSF alone patients will be boosted with GM-CSF alone). Patient blinding will be maintained throughout the study.