Menkir Tigist Ferede, Jbaily Abdulrahman, Verguet Stéphane
Center for Communicable Disease Dynamics, Department of Epidemiology, Harvard T.H. Chan School of Public Health, Harvard University, Boston, MA, USA.
Department of Global Health and Population, Harvard T.H. Chan School of Public Health, Harvard University, Boston, MA, USA.
Vaccine. 2021 May 18;39(21):2894-2900. doi: 10.1016/j.vaccine.2021.03.023. Epub 2021 Apr 15.
Deterministic compartmental models of infectious diseases like measles typically reflect biological heterogeneities in the risk of infection and severity to characterize transmission dynamics. Given the known association of socioeconomic status and increased vulnerability to infection and mortality, it is also critical that such models further incorporate social heterogeneities.
Here, we aimed to explore the influence of integrating income-associated differences in parameters of traditional dynamic transmission models. We developed a measles SIR model, in which the Susceptible, Infected and Recovered classes were stratified by income quintile, with income-specific transmission rates, disease-induced mortality rates, and vaccination coverage levels. We further provided a stylized illustration with secondary data from Ethiopia, where we examined various scenarios demonstrating differences in transmission patterns by income and in distributional vaccination coverage, and quantified impacts on disparities in measles mortality.
The income-stratified SIR model exhibited similar dynamics to that of the traditional SIR model, with amplified outbreak peaks and measles mortality among the poorest income group. All vaccination coverage strategies were found to substantially curb the overall number of measles deaths, yet most considerably for the poorest, with select strategies yielding clear reductions in measles mortality disparities.
The incorporation of income-specific differences can reveal distinct outbreak patterns across income groups and important differences in the subsequent effects of preventative interventions like vaccination. Our case study highlights the need to extend traditional modeling frameworks (e.g. SIR models) to be stratified by socioeconomic factors like income and to consider ensuing income-associated differences in disease-related morbidity and mortality. In so doing, we build on existing tools and characterize ongoing challenges in achieving health equity.
麻疹等传染病的确定性 compartmental 模型通常反映感染风险和严重程度方面的生物学异质性，以描述传播动态。鉴于社会经济地位与感染及死亡易感性增加之间的已知关联，此类模型进一步纳入社会异质性也至关重要。
在此，我们旨在探讨将与收入相关的差异纳入传统动态传播模型参数的影响。我们开发了一个麻疹 SIR 模型，其中易感、感染和康复类别按收入五分位数分层，具有特定收入的传播率、疾病导致的死亡率和疫苗接种覆盖率。我们还利用埃塞俄比亚的二手数据提供了一个程式化示例，在其中我们研究了各种情景，展示了不同收入水平下的传播模式差异以及疫苗接种覆盖率分布情况，并量化了对麻疹死亡率差异的影响。
收入分层的 SIR 模型呈现出与传统 SIR 模型相似的动态，最贫困收入群体中的疫情高峰和麻疹死亡率有所放大。所有疫苗接种覆盖率策略都被发现能大幅降低麻疹死亡总数，对最贫困群体的效果最为显著，某些策略能明显降低麻疹死亡率差异。
纳入特定收入差异可以揭示不同收入群体之间独特的疫情模式以及疫苗接种等预防性干预措施后续效果的重要差异。我们的案例研究强调了将传统建模框架（如 SIR 模型）扩展为按收入等社会经济因素分层，并考虑随之而来的与收入相关的疾病发病率和死亡率差异的必要性。通过这样做，我们在现有工具的基础上，描述了在实现健康公平方面持续存在的挑战。
