个体随机模型驱动的疫苗直接和间接效果评估  

Evaluation of direct and indirect effects of vaccines driven by an individual-based stochastic model

作　　者：郭怡超 郭晓豪 赵泽宇 陈田木 GUO Yichao;GUO Xiaohao;ZHAO Zeyu;CHEN Tianmu(State Key Laboratory of Vaccines for Infectious Diseases,School of Public Health,Xiamen University,Xiamen 361102,China)

机构地区：[1]传染病疫苗研发全国重点实验室,厦门大学公共卫生学院,福建厦门361102

出　　处：《厦门大学学报（自然科学版）》2024年第3期410-420,共11页Journal of Xiamen University：Natural Science

基　　金：国家重点研发计划(2021YFC2301604);中央高校基本科研业务费专项(20720230001)。

摘　　要：[目的]丰富国内疫苗效果评估策略,为制定免疫计划或筛选/候选疫苗提供科学依据.[方法]采用基于人群均匀混合假设的个体随机模型,以新型冠状病毒Omicron变异株为例,考虑疾病自然史、人群接触度、疫苗覆盖率和效果等因素,将个体层面疫苗的防感染和防传播效果推及群体层面的直接和间接效果.[结果]模拟结果分4个场景讨论仅提升疫苗覆盖率(vaccine coverage,VC)或仅提升疫苗效果(vaccine effectiveness,VE)的结局指标.当VE分别为0.5和0.9时,将VC从50%提升至90%,受间接效果保护人群的日新增感染率峰值的降幅分别为31.1%和72.1%,大于仅提升VE的场景;但仅提升VE的场景的直接效果不论在累积感染率还是日新增感染率指标上,均优于仅提升VC的场景.疫苗混合效果受直接效果影响较大;要实现10%以上的间接效果,至少需要接种覆盖90%以上的易感者,且疫苗防传播和防感染效果均超过85%,或其中一者接近90%,另一者接近80%.[结论]上述结果表明提升VE相比于提升VC在群体层面上更具有公共卫生学意义.但当前的新型冠状病毒疫苗防感染和防传播效果均不理想,因此加强个体接种来提升VC仍具有重要意义.间接效果随着VC的增加而增加,这将为群体中无法接种的个体提供一定保护作用.[Objective]Vaccination elicits a specific immune response in vaccinated individuals,resulting in direct effects such as preventing infection,reducing the severity of the disease after infection,and shortening the duration of transmission.In addition,mass vaccination can have indirect effects on unvaccinated people.In the evaluation of vaccines,randomized clinical trials can only assess the efficacy of vaccines under specific conditions and at the individual immunological level.Meanwhile,field trials can measure the effectiveness of vaccines in the real world but do not fully account for the indirect effects of vaccines on the possible impact of vaccination strategy.This study aims to enhance domestic vaccine effectiveness assessment strategies and provide a scientific basis for formulating immunization plans or selecting candidate vaccines.[Methods]This study employs an individual-based stochastic model based on the assumption of uniformly mixed populations,using the example of the Omicron variant of the SARS-CoV-2.It considers factors such as the natural history of the disease,contact patterns,vaccine coverage,and vaccine effectiveness.In each iteration,the close contacts of individual x are randomly generated,and the natural history status of the disease of all individuals is updated.The number of people in each natural history status and the number of new infections in the vaccinated and non-vaccinated groups at that time step are also calculated.The study extends the individual-level vaccine effects in preventing infection and transmission to direct and indirect effects at the population level.[Results]Simulation results discuss indexes in four scenarios,considering only the improvement of vaccine coverage(VC)or only the enhancement of vaccine effectiveness(VE).When VE is set at 0.5 and 0.9,respectively,increasing VC from 50%to 90%results in reductions of 31.1%and 72.1%in the peak daily infection rate of the population protected by indirect effects.These reductions are greater than those in scenarios focusing

关 键 词：个体随机模型 疫苗效果 群体免疫 新冠病毒 疫苗覆盖率 免疫计划 

分 类 号：R181.25[医药卫生—流行病学]