Evaluation of different immunization schedules for oral cholera B subunit-whole cell vaccine in Swedish volunteers

Different immunization schedules for oral B subunit-whole cell (B-WC) cholera vaccine were evaluated in Swedish volunteers to obtain information for recommendations of vaccine use in non-endemic areas. Two peroral doses of B-WC vaccine were as effective as three doses in inducing IgA and IgG antitoxin as well as vibriocidal antibody responses in serum. Administration of two vaccine doses either at 7, 14 or 28-42 day intervals resulted in comparable antitoxin responses in serum, whereas a 3-day immunization interval resulted in significantly lower titre increases. Vibriocidal antibody responses were comparable after the different time intervals tested (3-42 days). The B-WC vaccine can be effectively administered together with a cheap, commercially available sodium bicarbonate powder dissolved in water to protect the vaccine from gastric acid.