Comparison of the efficacy of Salmonella- andListeria-based vaccines in preventing the growth of murine fibrosarcoma F1.A11. After immunization with Salmonella SL7207 (pCMVβ; ▪), Listeria ▵mpl2pGK20 (⧫), and saline only (•) mice received a subcutaneous challenge with F1A11 tumor cells. Tumor growth was inspected every other day by palpation. Each group included 15 mice.