Caro J Jaime, Möller Jörgen, Getsios Denis, Coudeville L, El-Hadi Wissam, Chevat Catherine, Nguyen Van Hung, Caro Ingrid
Caro Research Institute, Concord, MA, USA.
BMC Public Health. 2007 Jun 29;7:130. doi: 10.1186/1471-2458-7-130.
Meningococcal disease can have devastating consequences. As new vaccines emerge, it is necessary to assess their impact on public health. In the absence of long-term real world data, modeling the effects of different vaccination strategies is required. Discrete event simulation provides a flexible platform with which to conduct such evaluations.
A discrete event simulation of the epidemiology of invasive meningococcal disease was developed to quantify the potential impact of implementing routine vaccination of adolescents in the United States with a quadrivalent conjugate vaccine protecting against serogroups A, C, Y, and W-135. The impact of vaccination is assessed including both the direct effects on individuals vaccinated and the indirect effects resulting from herd immunity. The simulation integrates a variety of epidemiologic and demographic data, with core information on the incidence of invasive meningococcal disease and outbreak frequency derived from data available through the Centers for Disease Control and Prevention. Simulation of the potential indirect benefits of vaccination resulting from herd immunity draw on data from the United Kingdom, where routine vaccination with a conjugate vaccine has been in place for a number of years. Cases of disease are modeled along with their health consequences, as are the occurrence of disease outbreaks.
When run without a strategy of routine immunization, the simulation accurately predicts the age-specific incidence of invasive meningococcal disease and the site-specific frequency of outbreaks in the Unite States. 2,807 cases are predicted annually, resulting in over 14,000 potential life years lost due to invasive disease. In base case analyses of routine vaccination, life years lost due to infection are reduced by over 45% (to 7,600) when routinely vaccinating adolescents 12 years of age at 70% coverage. Sensitivity analyses indicate that herd immunity plays an important role when this population is targeted for vaccination. While 1,100 cases are avoided annually when herd immunity effects are included, in the absence of any herd immunity, the number of cases avoided with routine vaccination falls to 380 annually. The duration of vaccine protection also strongly influences results.
In the absence of appropriate real world data on outcomes associated with large-scale vaccination programs, decisions on optimal immunization strategies can be aided by discrete events simulations such as the one described here. Given the importance of herd immunity on outcomes associated with routine vaccination, published estimates of the economic efficiency of routine vaccination with a quadrivalent conjugate vaccine in the United States may have considerably underestimated the benefits associated with a policy of routine immunization of adolescents.
脑膜炎球菌病可产生毁灭性后果。随着新疫苗的出现，有必要评估它们对公共卫生的影响。在缺乏长期真实世界数据的情况下，需要对不同疫苗接种策略的效果进行建模。离散事件模拟提供了一个灵活的平台来进行此类评估。
开发了一种侵袭性脑膜炎球菌病流行病学的离散事件模拟，以量化在美国对青少年实施常规接种四价结合疫苗（预防A、C、Y和W-135血清群）的潜在影响。评估疫苗接种的影响，包括对接种个体的直接影响和群体免疫产生的间接影响。该模拟整合了各种流行病学和人口统计学数据，侵袭性脑膜炎球菌病发病率和疫情频率的核心信息来自疾病控制和预防中心提供的数据。对群体免疫产生的疫苗接种潜在间接益处的模拟借鉴了英国的数据，在英国，结合疫苗的常规接种已经实施了数年。对疾病病例及其健康后果进行建模，对疾病爆发的发生情况也进行建模。
在没有常规免疫策略的情况下运行时，该模拟准确预测了美国侵袭性脑膜炎球菌病的年龄特异性发病率和特定地点的疫情频率。预计每年有2807例病例，因侵袭性疾病导致超过14000个潜在生命年损失。在常规疫苗接种的基础病例分析中，当对12岁青少年进行70%覆盖率的常规疫苗接种时，因感染导致的生命年损失减少超过45%（降至7600个）。敏感性分析表明，当针对该人群进行疫苗接种时，群体免疫起着重要作用。当纳入群体免疫效应时，每年可避免1100例病例，而在没有任何群体免疫的情况下，常规疫苗接种避免的病例数降至每年380例。疫苗保护的持续时间也对结果有很大影响。
在缺乏与大规模疫苗接种计划相关结果的适当真实世界数据的情况下，离散事件模拟（如此处所述的模拟）可有助于做出关于最佳免疫策略的决策。鉴于群体免疫对与常规疫苗接种相关结果的重要性，美国已发表的关于四价结合疫苗常规接种经济效率的估计可能大大低估了青少年常规免疫政策带来的益处。
