Impact of Imitation Processes on the Effectiveness of Ring Vaccination

Abstract

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.

Behavioural change models for infectious disease transmission: a systematic review (2010–2015)

“…[143], Schimit & Monteiro [158], Wells et al . [159], Morsky & Bauch [160], Ruan et al . [161], Campbell & Salathe [162], Wu et al .…”

“…We retrieved 26 papers [13,20,27–31,33,37–39,44,46,54,69,89,91,93,137,143,150,152,154,156,159,164] describing a BCM with an objective function with imitation. It is recognized that some social or peer influence should be incorporated in the decision-making process of the individuals (see also models with information as a dynamic parameter).…”

Conflicts of Interest during Contact Investigations: A Game-Theoretic Analysis

“…We also note that real decision making could take into account a much richer strategic set, so that individuals could have a different strategy depending on whether or not they know how many cases there have been, what other individuals have done, or other factors (e.g. [46,61,63,[70][71][72][73]). Finally, the limitations of modeling human behavior as governed by classical economic models of rational optimization have long been noted [74]; in disease control settings or emergency responses more generally, fear [75] as well as altruism [73,76,77] have been reported.…”

“…Game theory has been used in other investigations of disease transmission [46][47][48][49][50][51][52], especially for vaccines [49,[53][54][55][56][57][58], treatment decisions [59], and the use of social distancing during an epidemic [60]. The impact of strategic behavior has been explored in the context of ring vaccination, which requires contact investigation [61][62][63]. These analyses, however, examine vaccination choice and do not explore disclosure choice.…”

Ebola vaccines in clinical trial: The promising candidates

“…56 This trial used a cluster randomization design with a ring vaccination approach, which was used for smallpox eradication in the 1970s. 57 A cluster of individuals at high risk of infection defined as contacts or contacts of contacts because of their social or geographical association with the newly confirmed Ebola patient was randomized to receive one dose of rVSV-EBOV vaccine immediately or 21-day delayed. 4123 participants were assigned to immediate vaccination group, and 3528 participants were assigned to delayed vaccination group.…”