A cancer vaccine comprised of a recombinant, attenuated, replication-defective simian adenovirus vector (ChAdOx1) encoding the human 5T4 fetal oncoprotein (ChAdOx1.5T4), with potential immuno-activating and antineoplastic activities. Upon administration of the recombinant attenuated chimpanzee adenovirus 5T4 vaccine, the viral vector expresses 5T4 and stimulates the host immune system to mount a cytotoxic T-lymphocyte (CTL) response against tumor cells expressing 5T4, which results in tumor cell lysis. 5T4, a transmembrane glycoprotein, is overexpressed by a variety of cancer cell types; its expression is correlated with increased invasiveness.