The increased gene delivery within the tumor and strong reduction in liver off-targeting led to an improved tumor-to-liver ratio of 1.1 million for the HER2-retargeted, shielded virus compared to a ratio of 1300 for the unmodified HAdV5HVR7 upon intratumoral injection (Fig. 9b), and thus about a 1000-fold improvement. The gene discussed is ERBB2; the disease is neoplasm.