Safety, immunogenicity, and lot stability of the whole cell/recombinant B subunit (WC/rCTB) cholera vaccine in Peruvian adults and children

To assess the safety, immunogenicity, and lot stability of the whole cell/r ecombinant B subunit cholera vaccine, 2 lots manufactured in June 1991 and February 1992 were tested in January 1995. Two oral doses of vaccine or pla cebo given 2 weeks apart were given with buffer to 216 Peruvian adults and children. Symptoms were elicited for 3 days after each dose. Serum and plas ma specimens obtained from each volunteer before vaccination and 10-14 days after the second dose were tested for vibriocidal and anti-cholera toxin a ntibodies. The vaccine was well-tolerated. Nearly half of the 100 vaccinees had pre-vaccination vibpiocidal titers greater than or equal to 1:40. Elev ated titers were observed in 22% of 37 children 2-5 years of age compared w ith 66% of 63 vaccinees 6-65 years (P < 0.001). A greater than or equal to 2-fold serum vibriocidal response was observed in 55% of 100 vaccinees and 6% of 32 placebo recipients. An elevated prevaccination titer (greater than or equal to 1:40) did not change the proportion of vaccinees who responded with a greater than or equal to 2-fold increase in vibriocidal titer (51% versus 59%, difference not significant), but did change the proportion resp onding with a greater than or equal to 4-fold increase (41% versus 22%; P < 0.05). The vibriocidal seroconversion rate was lowest in children 2-5 year s old despite low pre-vaccination titers. Two-fold or greater serum antitox ic responses in IgA and IgG were observed in >90% of the vaccinees; greater than or equal to 4-fold responses were seen in 65-70% of the vaccinees wit h a 6-8-fold increase over baseline. Plasma specimens were as good as sera for determining anti-toxic antibodies by ELISA, but were less satisfactory for determining vibriocidal antibody titers.