[论文解读] SIR Simulation of COVID-19 Pandemic in Malaysia: Will the Vaccination Program be Effective?

W. K. Wong, Filbert H. Juwono+1 more|arXiv (Cornell University)|Jan 19, 2021

COVID-19 epidemiological studies被引用 15

一句话总结

本研究采用改进的SIR模型，模拟马来西亚新冠疫苗接种计划在吉隆坡、槟城、沙巴和沙捞越等高负担地区的影响。研究发现，即使每日接种率较低（0.138%），只要疫苗保护效力≥75%，即可显著降低感染峰值并使流行曲线趋于平缓，尤其在结合社交距离措施以降低R₀时效果更明显。

ABSTRACT

Since the end of 2019, COVID-19 has significantly affected the lives of people around the world. Towards the end of 2020, several COVID-19 vaccine candidates with relatively high efficacy have been reported in the final phase of clinical trials. Vaccines have been considered as critical tools for opening up social and economic activities, thereby lessening the impact of this disease on the society. This paper presents a simulation of COVID-19 spread using modified Susceptible-Infected-Removed (SIR) model under vaccine intervention in several localities of Malaysia, i.e. those cities or states with high relatively COVID-19 cases such as Kuala Lumpur, Penang, Sabah, and Sarawak. The results show that at different vaccine efficacy levels (0.75, 0.85, and 0.95), the curves of active infection vary slightly, indicating that vaccines with efficacy above 0.75 would produce the herd immunity required to level the curves. In addition, disparity is significant between implementing or not implementing a vaccination program. Simulation results also show that lowering the reproduction number, R0 is necessary to keep the infection curve flat despite vaccination. This is due to the assumption that vaccination is mostly carried out gradually at the assumed fixed rate. The statement is based on our simulation results with two values of R0: 1.1 and 1.2, indicative of reduction of R0 by social distancing. The lower R0 shows a smaller peak amplitude about half the value simulated with R0=1.2. In conclusion, the simulation model suggests a two-pronged strategy to combat the COVID-19 pandemic in Malaysia: vaccination and compliance with standard operating procedure issued by the World Health Organization (e.g. social distancing).

研究动机与目标

• 评估马来西亚国家疫苗接种计划在减少高发病率州属新冠传播方面的有效性。
• 评估不同疫苗保护效力水平（0.75、0.85、0.95）对局部地区流行病动态的影响。
• 研究疫苗接种与通过社交距离降低R₀的联合影响对感染峰值和日新增病例数的作用。
• 预测在实际约束条件（如接种速度缓慢和疫苗犹豫）下，疫苗接种带来的公共卫生效益。
• 为政策制定者提供一个用于评估疫苗接种与非药物干预双重策略的建模框架。

提出的方法

• 通过引入恒定的日接种率，将经典SIR模型进行改进，使易感者（S）直接转入康复者（R）群体。
• 将疫苗保护效力作为S到R转化速率的缩放因子，模拟部分免疫力。
• 采用两个基准R₀值（1.1和1.2），分别代表实施和未实施社交距离措施的情景。
• 将模型应用于马来西亚四个地区：吉隆坡、槟城、沙巴和沙捞越，使用各地区特定的人口规模。
• 模拟270天内接种与未接种情景，以比较感染峰值和累计病例数。
• 采用数值积分求解描述改进SIR动态的常微分方程组。

实验结果

研究问题

• RQ1 在疫苗保护效力为75%、85%和95%的情况下，马来西亚各州的活跃感染人数峰值如何变化？
• RQ2 每日接种率稳定但较低（0.138%人口/天）对流行曲线平缓化的影响是什么？
• RQ3 通过社交距离降低R₀与疫苗接种相结合，如何影响日新增病例峰值的降低？
• RQ4 与无疫苗接种相比，疫苗接种单独作用在多大程度上减轻了医疗系统的负担？
• RQ5 人口规模和传播动态的区域差异如何影响疫苗接种计划的有效性？

主要发现

• 在疫苗保护效力为0.75、0.85和0.95时，活跃感染曲线变化极小，表明保护效力超过75%即可实现群体免疫。
• 当R₀ = 1.2时，马来西亚的每日感染峰值约为20,000例（接种情景），而在无接种情景下为人口的1.7%（约540,000人）。
• 将R₀降至1.1可使每日感染峰值降至约6,000例，约为R₀ = 1.2时峰值的一半，凸显社交距离的重要性。
• 即使接种速度缓慢，疫苗接种计划仍将马来西亚的感染峰值降低约0.1%人口（3,200人）。
• 由于每日接种持续减少易感者（S）数量，感染人数（I）的梯度在接种情景中更早转为负值。
• 模型显示，随着更多个体被接种，累积免疫力随时间增加，即使存在持续的输入感染风险，传播率仍呈持续下降趋势。