FIELD TRIAL OF KILLED ORAL CHOLERA VACCINES IN VIETNAM

霍乱仍然是越南的一个重大公共卫生问题。在20世纪80年代后期，越南国家卫生和流行病学研究所以20世纪80年代中期孟加拉国分支研究人员测试的瑞典疫苗为模型开发了一种灭活口服霍乱疫苗。 在顺化对这种疫苗进行的一项实地试验招募了10万名受试者，发现这种疫苗对埃尔托霍乱的保护率约为60%，对幼儿和老年人的疗效相似。 这种早期的疫苗现已扩大到包括针对新确认的0139血清群霍乱弧菌的覆盖范围。 在河内的成人和儿童中进行了该疫苗安全性和免疫原性的随机、安慰剂对照预试验。每次预试验均发现疫苗是安全的，并诱导了可信的血清杀弧菌应答。根据这些有利的数据，1997年3月在沿海城市庆和开始了一项大规模的疫苗有效性实地试验，招募了30多万人。 1999年3月，根据1997年接受的研究药物对研究人群进行分层，并基于居住地的哈姆雷特，重新随机接受两剂疫苗或安慰剂方案。 目前正在对试验人群进行监测，以便能够估计疫苗接种后两年的临床有效性。

Cholera remains a significant public health problem in Vietnam. During the late 1980's, the National Institute of Hygiene and Epidemiology of Vietnam developed a killed oral cholera vaccine modeled on a Swedish vaccine tested by Branch investigators in Bangladesh during the mid-1980's. A field trial of this vaccine in Hue, which enrolled 100,000 subjects, found the vaccine to confer about 60% protection against El Tor cholera, with similar efficacy in young children and in older persons. This earlier vaccine has now been augmented to include coverage against the newly recognized 0139 serogroup of V. cholerae. Randomized, placebo-controlled pretests of the safety and immunogenicity of this vaccine were conducted in adults and in children in Hanoi. Each pretest found the vaccine to be safe and to induce credible serum vibriocidal responses. Based on these favorable data, a large-scale field trial of vaccine effectiveness,enrolling over 300,000 persons was initiated in the coastal city of Khanh Hoa in March 1997. In March 1999 the study population was stratified according to study agents received in 1997, and based on hamlet of residence, re-ramdomized to receive a two dose regimen of vaccine or placebo. Surveillance of the trial population is now in progress, enabling estimation of the clinical effectiveness of the vaccine over two years following vaccination.