Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario, Canada.
Bull Math Biol. 2011 Nov;73(11):2748-72. doi: 10.1007/s11538-011-9646-4. Epub 2011 Mar 16.
Ring vaccination can be a highly effective control strategy for an emerging disease or in the final phase of disease eradication, as witnessed in the eradication of smallpox. However, the impact of behavioural dynamics on the effectiveness of ring vaccination has not been explored in mathematical models. Here, we analyze a series of stochastic models of voluntary ring vaccination. Contacts of an index case base vaccinating decisions on their own individual payoffs to vaccinate or not vaccinate, and they can also imitate the behaviour of other contacts of the index case. We find that including imitation changes the probability of containment through ring vaccination considerably. Imitation can cause a strong majority of contacts to choose vaccination in some cases, or to choose non-vaccination in other cases-even when the equivalent solution under perfectly rational (non-imitative) behaviour yields mixed choices. Moreover, imitation processes can result in very different outcomes in different stochastic realizations sampled from the same parameter distributions, by magnifying moderate tendencies toward one behaviour or the other: in some realizations, imitation causes a strong majority of contacts not to vaccinate, while in others, imitation promotes vaccination and reduces the number of secondary infections. Hence, the effectiveness of ring vaccination can depend significantly and unpredictably on imitation processes. Therefore, our results suggest that risk communication efforts should be initiated early in an outbreak when ring vaccination is to be applied, especially among subpopulations that are heavily influenced by peer opinions.
环形疫苗接种可以是一种非常有效的控制策略，用于新兴疾病或在疾病根除的最后阶段，正如天花根除所见证的那样。然而，行为动态对环形疫苗接种效果的影响在数学模型中尚未得到探讨。在这里，我们分析了一系列自愿环形疫苗接种的随机模型。索引病例的接触者根据自己的个人收益来决定是否接种疫苗，他们也可以模仿索引病例的其他接触者的行为。我们发现，包括模仿在内，会极大地改变通过环形疫苗接种来遏制疾病的概率。在某些情况下，模仿可以导致大多数接触者选择接种疫苗，而在其他情况下，模仿会导致大多数接触者选择不接种疫苗——即使在完全理性（非模仿）行为下的等效解决方案导致混合选择。此外，模仿过程可能会导致从相同参数分布中采样的不同随机实现中产生非常不同的结果，从而放大向一种行为或另一种行为的适度倾向：在某些实现中，模仿会导致大多数接触者不接种疫苗，而在其他实现中，模仿会促进接种疫苗并减少二次感染的数量。因此，环形疫苗接种的有效性可能会显著且不可预测地取决于模仿过程。因此，我们的研究结果表明，当需要进行环形疫苗接种时，应在疫情爆发初期就开始进行风险沟通工作，尤其是在那些受到同伴意见严重影响的亚人群中。
