模拟加强疫苗接种对疾病流行病学的影响。

Modelling the effect of a booster vaccination on disease epidemiology.

作者信息

Alexander M E, Moghadas S M, Rohani P, Summers A R

机构信息

Institute for Biodiagnostics, National Research Council Canada, R3B 1Y6, Winnipeg, Manitoba, Canada.

出版信息

J Math Biol. 2006 Mar;52(3):290-306. doi: 10.1007/s00285-005-0356-0. Epub 2005 Nov 10.

Abstract

Despite the effectiveness of vaccines in dramatically decreasing the number of new infectious cases and severity of illnesses, imperfect vaccines may not completely prevent infection. This is because the immunity afforded by these vaccines is not complete and may wane with time, leading to resurgence and epidemic outbreaks notwithstanding high levels of primary vaccination. To prevent an endemic spread of disease, and achieve eradication, several countries have introduced booster vaccination programs. The question of whether this strategy could eventually provide the conditions for global eradication is addressed here by developing a seasonally-forced mathematical model. The analysis of the model provides the threshold condition for disease control in terms of four major parameters: coverage of the primary vaccine; efficacy of the vaccine; waning rate; and the rate of booster administration. The results show that if the vaccine provides only temporary immunity, then the infection typically cannot be eradicated by a single vaccination episode. Furthermore, having a booster program does not necessarily guarantee the control of a disease, though the level of epidemicity may be reduced. In addition, these findings strongly suggest that the high coverage of primary vaccination remains crucial to the success of a booster strategy. Simulations using estimated parameters for measles illustrate model predictions.

摘要

尽管疫苗在大幅减少新感染病例数量和疾病严重程度方面具有有效性,但不完善的疫苗可能无法完全预防感染。这是因为这些疫苗提供的免疫力并不完全,且可能随时间减弱,导致即便初次疫苗接种率很高,仍会出现疫情复发和流行爆发。为防止疾病的地方性传播并实现根除,一些国家已推出加强疫苗接种计划。本文通过建立一个季节性强迫数学模型来探讨这一策略最终是否能为全球根除创造条件。对该模型的分析从四个主要参数给出了疾病控制的阈值条件:初次疫苗接种覆盖率;疫苗效力;衰减率;以及加强接种率。结果表明,如果疫苗仅提供临时免疫力,那么通常单次接种无法根除感染。此外,尽管加强接种计划不一定能保证控制疾病,但可能会降低流行程度。此外,这些发现强烈表明,初次疫苗的高接种覆盖率对于加强接种策略的成功仍然至关重要。使用麻疹估计参数进行的模拟说明了模型预测结果。

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