Lung cancer is the leading cause of death from cancer worldwide. First-line therapy is based on stage at diagnosis and can include chemotherapy, radiation, and surgery. Despite advances, the prognosis for advanced-stage lung cancer is very poor. Vaccines with the capability to activate the host immune system may have a role in second-line therapy. Advances in the understanding of cellular and molecular immunology are forming the basis for improving vaccine therapy. Most trials to date have demonstrated safety but inconsistent efficacy. Further research is needed to enhance this potential.