Halloran M E, Haber M, Longini I M
Division of Biostatistics, Emory University School of Public Health, Atlanta, GA 30329.
Am J Epidemiol. 1992 Aug 1;136(3):328-43. doi: 10.1093/oxfordjournals.aje.a116498.
Interpretation and estimation of vaccine efficacy is complicated when the vaccine effect is heterogeneous across vaccinated strata. If a person has a certain susceptibility, or probability of becoming infected conditional on a specified exposure to infection, then one effect of a vaccine would be to reduce that susceptibility, possibly to zero. Vaccine efficacy is a function of the relative susceptibilities in the vaccinated and unvaccinated persons. Under heterogeneity of vaccine effect, a general expression for a summary vaccine efficacy parameter is a function of the vaccine efficacy in the different vaccinated strata weighted by the fraction of the vaccinated subpopulations in each stratum. Interpretation and estimability of the summary vaccine efficacy parameter depends on whether the strata are identifiable, and whether the heterogeneity is host- or vaccine-related. Bounds are derived for the summary vaccine efficacy when the strata are not identifiable for the case of an outbreak of an acute infectious disease. The upper bound assumes that everyone is equally affected by the vaccine, and the lower bound assumes that some are completely protected while others have no protection. The biologic interpretation of the two bounds is different.
当疫苗效果在不同接种层中存在异质性时，疫苗效力的解释和评估会变得复杂。如果一个人具有一定的易感性，即给定特定感染暴露条件下被感染的概率，那么疫苗的一个作用就是降低这种易感性，甚至可能降至零。疫苗效力是接种者和未接种者相对易感性的函数。在疫苗效果异质性的情况下，汇总疫苗效力参数的一般表达式是不同接种层中疫苗效力的函数，权重为各层接种亚人群的比例。汇总疫苗效力参数的解释和可估计性取决于各层是否可识别，以及异质性是与宿主相关还是与疫苗相关。对于急性传染病暴发且各层不可识别的情况，推导出了汇总疫苗效力的界限。上限假设每个人受疫苗的影响相同，下限假设一些人得到完全保护而另一些人没有保护。这两个界限的生物学解释是不同的。
