Chao D L, Park J K, Marks F, Ochiai R L, Longini I M, Halloran M E
Vaccine and Infectious Disease Division,Fred Hutchinson Cancer Research Center,Seattle,Washington,USA.
The International Vaccine Institute,Seoul,South Korea.
Epidemiol Infect. 2015 Dec;143(16):3520-7. doi: 10.1017/S0950268815000692. Epub 2015 May 4.
An individual's risk of infection from an infectious agent can depend on both the individual's own risk and protective factors and those of individuals in the same community. We hypothesize that an individual's exposure to an infectious agent is associated with the risks of infection of those living nearby, whether their risks are modified by pharmaceutical interventions or by other factors, because of the potential for transmission from them. For example, unvaccinated individuals living in a highly vaccinated community can benefit from indirect protection, or living near more children in a typhoid-endemic region (where children are at highest risk) might result in more exposure to typhoid. We tested this hypothesis using data from a cluster-randomized typhoid vaccine trial. We first estimated each individual's relative risk of confirmed typhoid outcome using their vaccination status and age. We defined a new covariate, potential exposure, to be the sum of the relative risks of all who live within 100 m of each person. We found that potential exposure was significantly associated with an individual's typhoid outcome, and adjusting for potential exposure affected estimates of vaccine efficacy. We suggest that it is useful and feasible to adjust for spatially heterogeneous distributions of individual-level risk factors, but further work is required to develop and test such approaches.
个体感染传染病病原体的风险既取决于个体自身的风险和保护因素，也取决于同一社区中其他人的风险和保护因素。我们假设，个体接触传染病病原体与居住在附近人群的感染风险相关，无论他们的风险是通过药物干预还是其他因素改变的，因为存在从他们那里传播的可能性。例如，生活在高疫苗接种率社区的未接种疫苗个体可从间接保护中受益，或者生活在伤寒流行地区（儿童风险最高）附近有更多儿童可能会导致更多接触伤寒。我们使用一项整群随机伤寒疫苗试验的数据对这一假设进行了检验。我们首先根据每个人的疫苗接种状况和年龄估计其确诊伤寒结果的相对风险。我们定义了一个新的协变量“潜在暴露”，即居住在每个人100米范围内所有人的相对风险之和。我们发现潜在暴露与个体的伤寒结果显著相关，并且对潜在暴露进行调整会影响疫苗效力的估计。我们认为，对个体层面风险因素的空间异质性分布进行调整是有用且可行的，但需要进一步开展工作来开发和检验此类方法。
