TOLERANCE AND IMMUNOGENICITY OF AN ORAL D OSE OF CVD 103-HGR, A LIVE ATTENUATED VIBRIO-CHOLERAE 01 STRAIN - A DOUBLE-BLIND-STUDY IN CHILEANADULTS

CVD 103-HgR is an attenuated, AB+, live, recombinant vaccine strain, d eveloped by deletion of the toxA gen in a virulent Vibrio cholerae 01, Inada classical strain (569B). In phase II studies conducted to date, CVD 103-HgR has been well tolerated and immunogenic in volunteers fro m both industrialized countries and cholera-endemic areas. In this stu dy of safety, immunogenicity and excretion, 81 Chilean adults were ran domly allocated to receive, in a double blind fashion, a single oral d ose of 5x10(9) FU of CVD 103-HgR or placebo, (5x10(9) heat-killed E. C oli K12 organisms), in 100 ml of buffered water Side effects were asse ssed by daily visits to the participants. Immunogenicity, (vibriocidal seroconversion), was investigated in blood drawn before and on days 8 and 28 after immunization, while stool cultures to assess excretion o f the vaccine strain were performed on specimens obtained on days 1 an d 7. None of the participants, (40 vaccinees and 41 placebo recipients ), experienced untoward effects during 30 minutes of close surveillanc e after ingestion of the preparation; upon follow up, neither adverse events were more frecuently reported by the vaccinees. 34/40 vaccinees , and 2/41 participants receiveing placebo had a significant raise, (> = fourfold), in their vibriocidal titers; (85 vs 2%, p < 0.001). The peak postimmunization geometric mean titer, (222), was ten fold higher than the baseline vibriocidal titer. The vaccine strain was recovered in stool cultures from 8 participants, one of them excreted the strai n in both specimens. We conclude that CVD-103-HgR is safe and immunoge nic in Chilean adults.