Field trial of oral cholera vaccines in Bangladesh: results from three-year follow-up.
The protective efficacy (PE) of B subunit killed whole-cell (BS-WC) and killed whole-cell-only (WC) oral cholera vaccines was assessed in a randomised double-blind field trial among children aged 2-15 years and women over 15 years in rural Bangladesh. Among the 62 285 subjects who received three doses of BS-WC, WC, or Escherichia coli K12 strain placebo, cumulative PE at 3 years of follow-up was 50% for BS-WC and 52% for WC. PE was similar against severe and non-severe cholera, but was significantly lower in children who were vaccinated at 2-5 years (26% for BS-WC; 23% for WC) than in older persons (63% for BS-WC; 68% for WC). Among persons vaccinated at 2-5 years, protection at 4-6 months of follow-up was similar to that for older persons, but rapidly waned thereafter and was not evident during the third year of follow-up. In contrast, persons vaccinated at older ages were protected even in the third year of follow-up (PE 40% for BS-WC; 62% for WC). PE was substantially higher against classical cholera (58% for BS-WC; 60% for WC) than against El Tor cholera (39% and 40%).
Clemens
J D
JD
International Centre for Diarrhoeal Disease Research, Dhaka, Bangladesh.
Sack
D A
DA
Harris
J R
JR
Van Loon
F
F
Chakraborty
J
J
Ahmed
F
F
Rao
M R
MR
Khan
M R
MR
Yunus
M
M
Huda
N
N
D000284:Administration, Oral; D000293:Adolescent; D000367:Age Factors; D001459:Bangladesh / Q000453:epidemiology; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D002771:Cholera / Q000145:classification / Q000453:epidemiology / Q000276:immunology / Q000517:prevention & control*; D022121:Cholera Vaccines / Q000008:administration & dosage / Q000009:adverse effects / Q000145:classification / Q000276:immunology*; D004311:Double-Blind Method; D004341:Drug Evaluation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D016032:Randomized Controlled Trials as Topic; D013997:Time Factors; D015164:Vaccines, Inactivated / Q000008:administration & dosage / Q000009:adverse effects / Q000145:classification / Q000276:immunology*
D022121:Cholera Vaccines; D015164:Vaccines, Inactivated