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Epidemiological and immunological evidence suggests that some vaccines can reduce all-cause mortality through nonspecific changes made to innate immune cells. Here, we present the first data to describe the nonspecific immunological impact of oral vaccination with live-attenuated Salmonella Typhi strain Ty21a. We vaccinated healthy adults with Ty21a and assessed aspects of innate and adaptive immunity over the course of 6 months. Changes to monocyte phenotype/function were observed for at least 3 months. Changes to innate and adaptive immune cell cytokine production in response to stimulation with vaccine and unrelated nonvaccine antigens were observed over the 6-month study period. The changes that we have observed could influence susceptibility to infection through altered immune responses mounted to subsequently encountered pathogens. These changes could influence all-cause mortality.

Original publication




Journal article


Sci Adv

Publication Date





Administration, Oral, Adult, CD4-Positive T-Lymphocytes, Cytokines, Female, Healthy Volunteers, Humans, Male, Middle Aged, Monocytes, Polysaccharides, Bacterial, Salmonella typhi, Typhoid Fever, Typhoid-Paratyphoid Vaccines, Vaccination, Vaccines, Attenuated, Young Adult