Haber M, Longini I M, Halloran M E
Division of Biostatistics, Emory University School of Public Health, Atlanta, Georgia 30322.
Stat Med. 1991 Oct;10(10):1573-84. doi: 10.1002/sim.4780101009.
In a previous paper we defined the efficacy of a vaccine as 1-beta 1/beta 0, where beta 0 is the instantaneous probability of transmission of infection to an unvaccinated person exposed to a single infectious person, and beta 1 is similarly defined for a vaccinated person. We showed that under the conditions of an outbreak of an acute, directly transmitted infectious disease in a homogeneous and randomly mixing population, an estimate of this measure of vaccine efficacy is 1-[1n(1-A1)/1n(1-A0)], where A0 and A1 are the observed final attack rates among unvaccinated and vaccinated persons, respectively. In the present work we present an approximation for the standard error of this estimator, accounting for both the sampling and process variation. We extend the results of our previous paper to a stratified population, where the strata correspond to different levels of susceptibility and may have different vaccination coverage. We also consider populations that consist of small units (for example, households) where individuals mix primarily in these units. In this case, definition of vaccine efficacy is in terms of the within-unit transmission probabilities and is estimable by using transmission models for infectious diseases. We apply the estimation methods described above to data from influenza and measles outbreaks. We also examine, via a stochastic simulation study, the robustness of the vaccine efficacy estimators under various population structures and mixing patterns.
在之前的一篇论文中，我们将疫苗效力定义为1 - β1/β0，其中β0是未接种疫苗的人接触单个传染源时被感染的瞬时概率，β1对接种疫苗的人也作类似定义。我们表明，在同质且随机混合的人群中爆发急性直接传播传染病的情况下，这种疫苗效力衡量指标的一个估计值为1 - [ln(1 - A1)/ln(1 - A0)]，其中A0和A1分别是未接种疫苗者和接种疫苗者中观察到的最终发病率。在本研究中，我们给出了这个估计量标准误差的一个近似值，同时考虑了抽样误差和过程变异。我们将之前论文的结果扩展到分层人群，其中各层对应不同的易感性水平且可能有不同的疫苗接种覆盖率。我们还考虑由小单位（例如家庭）组成的人群，其中个体主要在这些单位内混合。在这种情况下，疫苗效力的定义依据单位内的传播概率，并且可以通过使用传染病传播模型来估计。我们将上述估计方法应用于流感和麻疹爆发的数据。我们还通过一项随机模拟研究，考察了在各种人群结构和混合模式下疫苗效力估计量（值）的稳健性。
