Voluntary vaccination may not stop monkeypox outbreak: A game-theoretic model

The effect of heterogeneity of relative vaccine costs on the mean population vaccination rate with mpox as an example

Mpox (formerly known as monkeypox) is a neglected tropical disease that became notorious during its 2022-2023 worldwide outbreak. The vaccination was available, but there were inequities in vaccine access. In this paper, we extend existing game-theoretic models to study a population that is heterogeneous in the relative vaccination costs. We consider a population with two groups. We determine the Nash equilibria (NE), i.e., optimal vaccination rates, for each of the groups. We show that the NE always exists and that, for a narrow range of parameter values, there can be multiple NEs. We focus on comparing the mean optimal vaccination rate in the heterogeneous population with the optimal vaccination rate in the corresponding homogeneous population. We show that there is a critical size for the group with lower relative costs and the mean optimal vaccination in the heterogeneous population is more than in the homogeneous population if and only if the group is larger than the critical size.

Knowledge, Attitude, and Behavior of the Pakistani Population Toward the Monkeypox Pandemic and the Associated Factors

Background Monkeypox (Mpox) is a virulent disease caused by orthopoxvirus. Mpox is emerging as a major global health threat. Currently, more than 100 countries are facing outbreaks. Pakistan, too, is witnessing the spread of this virus, with 11 confirmed cases and one death since its first detection in April 2023. Mpox infection can be diagnosed using polymerase chain reaction (PCR) and treated with antiviral agents. The smallpox vaccine is also proven to be effective against Mpox. Methodology This cross-sectional survey aimed to evaluate the knowledge, attitude, and behaviors (KAB) of the Pakistani population toward the Mpox pandemic and determine the factors affecting it. Data were collected through Google Forms using a validated questionnaire to assess the population's KAB. In total, 1,511 individuals were included in the final analysis. Results Study participants had good knowledge of the disease, poor attitude toward Mpox risk and severity, and poor behavior with low adherence to recommended protocols. Overall, 58% (n = 888) of the participants were male, and most of the respondents were aged between 18 and 30 years (n = 743, 49.2%). Most participants were married (n = 983, 65.1%), from urban areas (n = 837, 55.4%), and living in shared households (n = 876, 58%). Age showed a significant relationship with knowledge level and behavior, but not with attitude. The 18-30-year age group demonstrated higher knowledge levels (p = 0.007), regardless of gender. Shared households were significantly associated with a higher incidence of good knowledge (p < 0.05) compared to independent households (p = 0.038). Additionally, higher income was linked to better attitudes and behaviors. KAB outcomes also varied significantly based on marital status, individual education level, and parents' education levels. Conclusions Population dynamics such as cultural norms, religious beliefs, misperceptions about the disease associated with sexual behavior, health literacy, education level, rural and urban division of the population, gender role, migrant and refugee population, poverty, cost-seeking healthcare, and distrust in the government and healthcare system should be considered when constructing a public health policy because the behavior of the population is important for the implementation of preventive measures.

A mathematical model of visceral leishmaniasis transmission and control: Impact of ITNs on VL prevention and elimination in the Indian subcontinent

Visceral Leishmaniasis (VL) is a deadly, vector-borne, parasitic, neglected tropical disease, particularly prevalent on the Indian subcontinent. Sleeping under the long-lasting insecticide-treated nets (ITNs) was considered an effective VL prevention and control measures, until KalaNet, a large trial in Nepal and India, did not show enough supporting evidence. In this paper, we adapt a biologically accurate, yet relatively simple compartmental ordinary differential equations (ODE) model of VL transmission and explicitly model the use of ITNs and their role in VL prevention and elimination. We also include a game-theoretic analysis in order to determine an optimal use of ITNs from the individuals' perspective. In agreement with the previous more detailed and complex model, we show that the ITNs coverage amongst the susceptible population has to be unrealistically high (over 96%) in order for VL to be eliminated. However, we also show that if the whole population, including symptomatic and asymptomatic VL cases adopt about 90% ITN usage, then VL can be eliminated. Our model also suggests that ITN usage should be accompanied with other interventions such as vector control.

Exploring self-care practices and health beliefs among men in the context of emerging infectious diseases: Lessons from the Mpox pandemic in Brazil

Our goal was to explore self-care practices among men who have sex with men in the context of Mpox in Brazil. This study used qualitative research methods, including interviews and thematic analysis, to collect and analyze data from male participants across the Brazilian territory. The narratives unveil men's perspectives on self-care, risk reduction, and health beliefs during the Mpox pandemic. Our findings highlight a multifaceted approach to self-care among men, encompassing hygiene, physical contact management, mask usage, skin lesion vigilance, and adherence to official guidelines. Men's attitudes toward sexual behaviors emphasize the importance of reducing sexual partners, practicing safe sex, and combating misinformation through accurate information dissemination. The development of these behaviors and self-care practices can be facilitated by nurses guided by Dorothea Orem's Self-Care Theory, supported by patient-centered care, with strategies to address and confront the stigma associated with the disease and provide emotional support. Thus, the study underscores the pivotal role of self-care in mitigating infection risks, especially in the context of emerging infectious diseases. It acknowledges the impact of socio-cultural factors and healthcare policies on men's preventive measures. However, it also recognizes limitations, such as potential bias due to stigma concerns and a nonrepresentative sample. Ultimately, the research advocates for tailored education, promotion of gender equity, and healthcare empowerment to effectively manage health risks in such contexts.

A dynamic game of lymphatic filariasis prevention by voluntary use of insecticide treated nets

Lymphatic filariasis (LF) has been targeted for elimination as a public health concern by 2030 with a goal to keep the prevalence of LF infections under the 1% threshold. While mass drug administration (MDA) is a primary strategy recommended by WHO, the use of insecticide treated nets (ITN) plays a crucial role as an alternative strategy when MDA cannot be used. In this paper, we use imitation dynamics to incorporate human behavior and voluntary use of ITN into the compartmental epidemiological model of LF transmission. We find the equilibrium states of the dynamics and the ITN usage as it depends on epidemiological parameters and the cost of ITNs. We investigate the conditions under which the voluntary use of ITNs can keep the LF prevalence under the 1% threshold. We found that when the cost of using the ITNs is about 105 smaller than the perceived cost of LF, then the voluntary use of ITNs will eliminate LF as a public health concern. Furthermore, when the ITNs are given away for free, our model predicts that over 80% of the population will use them which would eliminate LF completely in regions where Anopheles are the primary vectors.

Behavioral game of quarantine during the monkeypox epidemic: Analysis of deterministic and fractional order approach

This work concerns the epidemiology of infectious diseases like monkeypox (mpox) in humans and animals. Our models examine transmission scenarios, including transmission dynamics between humans, animals, and both. We approach this using evolutionary game theory, specifically the intervention game-theoretical (IGT) framework, to study how human behavior can mitigate disease transmission without perfect vaccines and treatments. To do this, we use non-pharmaceutical intervention, namely the quarantine policy, which demonstrates the delayed effect of the epidemic. Additionally, we contemplate quarantine-based behavioral intervention policies in deterministic and fractional-order models to show behavioral impact in the context of the memory effect. Firstly, we extensively analyzed the model's positivity and boundness of the solution, reproduction number, disease-free and endemic equilibrium, possible stability, existence, concavity, and Ulam-Hyers stability for the fractional order. Subsequently, we proceeded to present a numerical analysis that effectively illustrates the repercussions of varying quarantine-related factors, information probability, and protection probability. We aimed to comprehensively examine the effects of non-pharmaceutical interventions on disease control, which we conveyed through line graphs and 2D heat maps. Our findings underscored the significant influence of strict quarantine measures and the protection of both humans and animals in mitigating disease outbreaks. These measures not only significantly curtailed the spread of the disease but also delayed the occurrence of the epidemic's peak. Conversely, when quarantine maintenance policies were implemented at lower rates and protection levels diminished, we observed contrasting outcomes that exacerbated the situation. Eventually, our analysis revealed the emergence of animal reservoirs in cases involving disease transmission between humans and animals.

Mathematical model of voluntary vaccination against schistosomiasis

Human schistosomiasis is a chronic and debilitating neglected tropical disease caused by parasitic worms of the genus Schistosoma. It is endemic in many countries in sub-Saharan Africa. Although there is currently no vaccine available, vaccines are in development. In this paper, we extend a simple compartmental model of schistosomiasis transmission by incorporating the vaccination option. Unlike previous models of schistosomiasis transmission that focus on control and treatment at the population level, our model focuses on incorporating human behavior and voluntary individual vaccination. We identify vaccination rates needed to achieve herd immunity as well as optimal voluntary vaccination rates. We demonstrate that the prevalence remains too high (higher than 1%) unless the vaccination costs are sufficiently low. Thus, we can conclude that voluntary vaccination (with or without mass drug administration) may not be sufficient to eliminate schistosomiasis as a public health concern. The cost of the vaccine (relative to the cost of schistosomiasis infection) is the most important factor determining whether voluntary vaccination can yield elimination of schistosomiasis. When the cost is low, the optimal voluntary vaccination rate is high enough that the prevalence of schistosomiasis declines under 1%. Once the vaccine becomes available for public use, it will be crucial to ensure that the individuals have as cheap an access to the vaccine as possible.

A fractional order Monkeypox model with protected travelers using the fixed point theorem and Newton polynomial interpolation

This study formulates a Monkeypox model with protected travelers. The fixed point theorem is used to obtain the existence and uniqueness of the solution with Ulam-Hyers stability for the analysis of the solution to the model. The Newton polynomial interpolation scheme is employed to solve an approximate solution of the fractional Monkeypox model. The numerical simulations and the graphical representations suggest that the fractional order affects the dynamics of the Monkeypox. The fractional order shows other underlining transmission trends of the Monkeypox disease. We conclude that the result obtained for each compartment conforms to reality as the fractional order approaches unity.

Rational social distancing in epidemics with uncertain vaccination timing

During epidemics people may reduce their social and economic activity to lower their risk of infection. Such social distancing strategies will depend on information about the course of the epidemic but also on when they expect the epidemic to end, for instance due to vaccination. Typically it is difficult to make optimal decisions, because the available information is incomplete and uncertain. Here, we show how optimal decision-making depends on information about vaccination timing in a differential game in which individual decision-making gives rise to Nash equilibria, and the arrival of the vaccine is described by a probability distribution. We predict stronger social distancing the earlier the vaccination is expected and also the more sharply peaked its probability distribution. In particular, equilibrium social distancing only meaningfully deviates from the no-vaccination equilibrium course if the vaccine is expected to arrive before the epidemic would have run its course. We demonstrate how the probability distribution of the vaccination time acts as a generalised form of discounting, with the special case of an exponential vaccination time distribution directly corresponding to regular exponential discounting.

Monkeypox: a review of epidemiological modelling studies and how modelling has led to mechanistic insight

Human monkeypox (mpox) virus is a viral zoonosis that belongs to the Orthopoxvirus genus of the Poxviridae family, which presents with similar symptoms as those seen in human smallpox patients. Mpox is an increasing concern globally, with over 80,000 cases in non-endemic countries as of December 2022. In this review, we provide a brief history and ecology of mpox, its basic virology, and the key differences in mpox viral fitness traits before and after 2022. We summarize and critique current knowledge from epidemiological mathematical models, within-host models, and between-host transmission models using the One Health approach, where we distinguish between models that focus on immunity from vaccination, geography, climatic variables, as well as animal models. We report various epidemiological parameters, such as the reproduction number, R0, in a condensed format to facilitate comparison between studies. We focus on how mathematical modelling studies have led to novel mechanistic insight into mpox transmission and pathogenesis. As mpox is predicted to lead to further infection peaks in many historically non-endemic countries, mathematical modelling studies of mpox can provide rapid actionable insights into viral dynamics to guide public health measures and mitigation strategies.

Imperfect vaccine can yield multiple Nash equilibria in vaccination games

As infectious diseases continue to threaten communities across the globe, people are faced with a choice to vaccinate, or not. Many factors influence this decision, such as the cost of the disease, the chance of contracting the disease, the population vaccination coverage, and the efficacy of the vaccine. While the vaccination games in which individuals decide whether to vaccinate or not based on their own interests are gaining in popularity in recent years, the vaccine imperfection has been an overlooked aspect so far. In this paper we investigate the effects of an imperfect vaccine on the outcomes of a vaccination game. We use a simple SIR compartmental model for the underlying model of disease transmission. We model the vaccine imperfection by adding vaccination at birth and maintain a possibility for the vaccinated individual to become infected. We derive explicit conditions for the existence of different Nash equilibria, the solutions of the vaccination game. The outcomes of the game depend on the complex interplay between disease transmission dynamics (the basic reproduction number), the relative cost of the infection, and the vaccine efficacy. We show that for diseases with relatively low basic reproduction numbers (smaller than about 2.62), there is a little difference between outcomes for perfect or imperfect vaccines and thus the simpler models assuming perfect vaccines are good enough. However, when the basic reproduction number is above 2.62, then, unlike in the case of a perfect vaccine, there can be multiple equilibria. Moreover, unless there is a mandatory vaccination policy in place that would push the vaccination coverage above the value of unstable Nash equilibrium, the population could eventually slip to the "do not vaccinate" state. Thus, for diseases that have relatively high basic reproduction numbers, the potential for the vaccine not being perfect should be explicitly considered in the models.