预防地方性流行的最佳疫苗接种策略:一个随机模型。

Optimal vaccination policy to prevent endemicity: a stochastic model.

作者信息

Foutel-Rodier Félix, Charpentier Arthur, Guérin Hélène

机构信息

Department of Statistics, University of Oxford, Oxford, UK.

Département de Mathématiques, Université du Québec à Montréal, Montréal, Canada.

出版信息

J Math Biol. 2024 Dec 19;90(1):10. doi: 10.1007/s00285-024-02171-z.

Abstract

We examine here the effects of recurrent vaccination and waning immunity on the establishment of an endemic equilibrium in a population. An individual-based model that incorporates memory effects for transmission rate during infection and subsequent immunity is introduced, considering stochasticity at the individual level. By letting the population size going to infinity, we derive a set of equations describing the large scale behavior of the epidemic. The analysis of the model's equilibria reveals a criterion for the existence of an endemic equilibrium, which depends on the rate of immunity loss and the distribution of time between booster doses. The outcome of a vaccination policy in this context is influenced by the efficiency of the vaccine in blocking transmissions and the distribution pattern of booster doses within the population. Strategies with evenly spaced booster shots at the individual level prove to be more effective in preventing disease spread compared to irregularly spaced boosters, as longer intervals without vaccination increase susceptibility and facilitate more efficient disease transmission. We provide an expression for the critical fraction of the population required to adhere to the vaccination policy in order to eradicate the disease, that resembles a well-known threshold for preventing an outbreak with an imperfect vaccine. We also investigate the consequences of unequal vaccine access in a population and prove that, under reasonable assumptions, fair vaccine allocation is the optimal strategy to prevent endemicity.

摘要

我们在此研究反复接种疫苗和免疫力下降对人群中地方性平衡建立的影响。引入了一个基于个体的模型,该模型考虑了感染期间传播率和后续免疫力的记忆效应,并考虑了个体层面的随机性。通过让种群规模趋于无穷大,我们推导出一组描述该流行病大规模行为的方程。对模型平衡点的分析揭示了地方性平衡存在的一个标准,该标准取决于免疫力丧失率和加强剂量之间的时间分布。在这种情况下,疫苗接种政策的结果受到疫苗阻断传播的效率以及加强剂量在人群中的分布模式的影响。与间隔不规则的加强针相比,在个体层面上间隔均匀的加强针策略在预防疾病传播方面被证明更有效,因为更长时间不接种疫苗会增加易感性并促进更有效的疾病传播。我们给出了为根除疾病而遵守疫苗接种政策所需的人群临界比例的表达式,它类似于一个众所周知的预防使用效果不佳的疫苗爆发的阈值。我们还研究了人群中疫苗获取不平等的后果,并证明在合理假设下,公平的疫苗分配是预防地方性流行的最优策略。

https://cdn.ncbi.nlm.nih.gov/pmc/blobs/bd2a/11655619/a9957dd4a62d/285_2024_2171_Fig1_HTML.jpg

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