FIELD TRIAL OF KILLED ORAL CHOLERA VACCINES IN VIETNAM

霍乱在越南仍然是一个重大的公共卫生问题。20世纪80年代末，越南国家卫生和流行病学研究所研制了一种口服灭活霍乱疫苗，其模型是1980年代中期该研究所的调查人员在孟加拉国试验的瑞典疫苗。在顺化对该疫苗进行了实地试验，招募了10万名受试者，结果发现该疫苗对埃尔托尔霍乱的保护作用约为60%，对幼儿和老年人也有类似的效果。这种早期疫苗现已得到扩大，包括针对新确认的0139霍乱弧菌血清群的疫苗。在河内的成人和儿童中进行了该疫苗的安全性和免疫原性的随机、安慰剂对照预试验。每次预试验都发现疫苗是安全的，并能诱发可靠的血清杀弧菌反应。根据这些有利的数据，1997年3月在沿海城市庆化开始了疫苗有效性的大规模实地试验，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，并以居住村庄为基础，重新随机分组，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，以便在接种疫苗后两年内对疫苗的临床有效性进行估计。

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.