考虑间接效应估计的疫苗现场试验设计

Design of field studies on vaccines which involves capturing indirect effect

多数疫苗在人群中使用后会产生直接效应和间接效应,除接种者得到保护外,项目实施人群中的未种者也能因此受益.而传统的疫苗临床试验设计,采用个体随机化分组方式,由于不能对间接效应进行定量估计,干预措施的成本效益往往被低估.文中介绍Halloran等构建的包含间接效应估计的干预试验设计框架,提供包括直接效应、间接效应、总效应和整体效应等指标的计算方法,并阐述各类效应的意义及其相互关系,结合在孟加拉国开展的口服霍乱疫苗和在印度开展的伤寒vi疫苗两个现场试验实例,对间接效应的识别及其实际应用价值等内容作进一步探讨,为研究人员设计疫苗现场试验方案提供参考.

For most variety of vaccines, two types of effects-direct and indirect, can result from immunization programs. Unimmunized individuals in the population that receive immunization program can benefit from the vaccines in addition to the protection from immunization.The classical vaccine trails allocate individuals into study and control arms with individual randomization, so the programs＇ cost-benefit is underestimated due to the impossible measurement on indirect effect. The objectives of the present work are to introduce the conceptual framework,developed by Halloran et al, for four types of study designs that differentiate and account for direct,indirect, total and overall effects of intervention programs, and to explain the relationships of these effects as well. With the examples of field trails of oral cholera vaccines in Bangladesh and Vi typhoid vaccine in India, further issues refer to the identification of indirect effect. The application in practice is also discussed.