The immune response to different dosage schedules of oral live Salmonella typhi Ty21a
vaccines was studied by enumeration of specific antibody-secreting cells (ASC) in the
peripheral blood believed to have been stimulated by the vaccine antigen on mucosal
surfaces and to be on their way back to those sites for local antibody secretion. Four groups
of subjects were vaccinated with either three (3× S), two (2× S) or one (1× S) dose of a
suspension-formulated vaccine, or with three doses of vaccine in enteric-coated capsules …