FIELD TRIAL OF KILLED ORAL CHOLERA VACCINES IN VIETNAM

在越南，霍乱仍然是一个严重的公共卫生问题。在20世纪80年代末，越南国家卫生与流行病学研究所研发了一种口服霍乱灭活疫苗，仿照80年代中期S在孟加拉国的分支机构调查人员测试的一种瑞典疫苗。这种疫苗在顺化进行的现场试验有100,000名受试者，发现该疫苗对埃尔托霍乱有大约60%的保护作用，对幼儿和老年人也有类似的效果。这一早期的疫苗现在已经扩大到包括针对新发现的0139霍乱弧菌血清群的覆盖范围。在河内对成人和儿童进行了这种疫苗的安全性和免疫原性的随机、安慰剂对照的预测试。每一次预试都发现疫苗是安全的，并能诱导可靠的血清杀弧菌反应。基于这些有利的数据，1997年3月在沿海城市清华启动了一项大规模的疫苗有效性现场试验，招募了30多万人。1999年3月，研究人群根据1997年收到的研究试剂进行分层，并根据居住的村庄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，以便在接种疫苗后两年内评估疫苗的临床效果。

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.