Purified Poli Vi antigen has been used in the formulation of a parenteral vaccine against typhoid fever [11] but has never been used by a mucosal route as a with vaccine purposes. Mucosal immunization has been approached by administration by the oral route of the attenuated S. Typhi strain CVD 909 (HolaVax-Typhoid®) expressing the Vi polysaccharide [7]. The gene discussed is POLI; the disease is typhoid fever.